Co-reporter:Weixing Yang, Yu Zhang, Tianyu Liu, Rui Huang, Songgang Chai, Feng Chen, and Qiang Fu
ACS Sustainable Chemistry & Engineering October 2, 2017 Volume 5(Issue 10) pp:9102-9102
Publication Date(Web):September 1, 2017
DOI:10.1021/acssuschemeng.7b02012
Graphene films receive tremendous attention due to their ultrahigh electrical and thermal conductivities, which show great application prospects in modern electronic devices. However, the brittleness and low strength of graphene films largely limit their use in advanced applications. And the preparation processes of graphene films reported so far are also not completely green. In this work, a novel strong and green graphene composite film with outstanding electromagnetic interference shielding effectiveness (EMI SE), electrical and thermal conductivities was successfully fabricated by using nanofibrillated cellulose (NFC) as dispersing agent and mechanical compression. In this way, graphene nanosheets (GNs) were not only efficiently dispersed in the aqueous solution but also linked together by NFC to enhance mechanical strength of the prepared films. Simultaneously, mechanical compression could powerfully induce strong alignment and increase the contact area of the GNs. As a result, the optimum electrical and thermal conductivities of the obtained films reached up to 988.2 S cm–1 and 240.5 W m–1 K–1, respectively, along with a high tensile strength of 61 MPa and a superior EMI SE of 43 dB with only ≈13 μm in thickness. Even more, the resultant films revealed excellent flame resistance. And the NFC can be removed by burning the films, resulting in complete graphene films with much higher electrical and thermal conductivities. The manufacturing route in our study is facile, cost-effective and completely green for the preparation of strong and highly conductive graphene-based thin films.Keywords: Electrical conductivity; Electromagnetic interference shielding; Graphene; Nanofibrillated cellulose; Thermal conductivity;
Co-reporter:Dongyu Bai, Huili Liu, Hongwei Bai, Qin Zhang, and Qiang Fu
Macromolecules October 10, 2017 Volume 50(Issue 19) pp:7611-7611
Publication Date(Web):September 29, 2017
DOI:10.1021/acs.macromol.7b01794
Stereocomplex (SC) crystallization between high-molecular-weight poly(l-lactide) (PLLA) and poly(d-lactide) (PDLA) provides a promising route to substantially improve the properties of polylactide (PLA), but conventional melt processing of the SC-type PLA (SC-PLA) is nearly impossible primarily due to the poor crystallization memory effect as well as serious thermal degradation after complete melting of SC crystallites with high melting temperatures of above 220 °C. Recently, we reported an innovative low-temperature (180–210 °C) sintering technology for fabricating SC-PLA products from its nascent powder. Unfortunately, its practical application has been significantly hindered by an extremely high pressure of 1 GPa, which must be utilized to ensure good surface wetting of the densified powder particles. With this challenge in mind, herein, the role of powder crystallinity in the low-temperature sintering has been investigated. Interestingly, we first demonstrate that depressing powder crystallinity is favorable for the particle wetting under a much lower pressure during the densification stage of the nascent powders because the deformation of the powders becomes easier with the decrease in the fraction of rigid crystal network. Moreover, during the subsequent interface welding stage, more PLLA/PDLA chains could be involved in the interdiffusion and SC crystallization across particle interfaces, thus forming large amounts of new SC crystallites capable of tightly welding the interfaces. As a consequence, SC-PLA sheets with excellent heat resistance and mechanical properties have been successfully fabricated by sintering under a pressure of as low as 300 MPa. Overall, these fascinating findings not only provide new fundamental understandings on the role of initial crystallinity in the low-temperature sintering of SC-PLA powder but also indicate an avenue toward industrial-scale fabrication of SC-PLA products from low-crystallinity nascent powder using conventional polymer sintering equipment.
Co-reporter:Yuanlin Luo, Yilong Ju, Hongwei Bai, Zhenwei Liu, Qin Zhang, and Qiang Fu
The Journal of Physical Chemistry B June 29, 2017 Volume 121(Issue 25) pp:6271-6271
Publication Date(Web):June 6, 2017
DOI:10.1021/acs.jpcb.7b03976
Stereocomplex (SC) crystallites, formed between poly(l-lactide) (PLLA) and poly(d-lactide), exhibit great potential to substantially enhance crystallization rate of PLLA-based materials as an eco-friendly nucleating agent. However, the nucleation efficiency of the SC crystallites is still far below an expected level, mostly on account of their strong aggregation tendency in PLLA/PDLA melts. Herein, taking PLLA/poly(ethylene-methyl acrylate-glycidyl methacrylate) (E-MA-GMA) blends as an example, we report a unique and facile strategy to control the dispersion and distribution of SC crystallites within the PLLA matrix by using elastomeric E-MA-GMA as carrier for the incorporation of PDLA. To do this, PDLA was first blended with E-MA-GMA or chemically grafted onto the E-MA-GMA. During subsequent melt-blending of PLLA and the E-MA-GMA/PDLA master batch, the PDLA chain clusters predispersed in the E-MA-GMA phase can gradually migrate into PLLA matrix and then collaborate with the matrix chains to form large amounts of tiny and well-dispersed SC crystallites. Compared with the SC-crystallite agglomerates formed by the direct melt-blending of PLLA and PDLA components, such tiny SC crystallites are much more effective in accelerating PLLA matrix crystallization. More interestingly, when PDLA chains are grafted onto the EMA-GMA, the formed SC crystallites tend to preferentially distribute at the blend interface and thus induce not only optimal nucleation efficiency but also superior impact toughness because these interface-localized SC crystallites can also serve as bridges to enhance interface adhesion. This work could open a new avenue in designing heat-resistant and supertough PLLA blends via controllable construction of SC crystallites.
Co-reporter:Shuman Xu;Wenjin Yu;Mengfan Jing;Rui Huang;Qin Zhang
The Journal of Physical Chemistry C February 2, 2017 Volume 121(Issue 4) pp:2108-2117
Publication Date(Web):January 10, 2017
DOI:10.1021/acs.jpcc.6b11783
Stretchable sensors have drawn a great deal of attention due to their importance and necessity in high-technology areas. However, it is difficult to obtain sensors with high sensitivity accompanied by high tenacity. Taking advantage of the very large aspect ratio and amphiphilicity of nanofibrillated cellulose (NFC), in this study, we fabricated polyurethane (TPU)/multiwall carbon nanotube (CNT) nanocomposites with excellent dispersion using NFC as stabilizer. Then the mechanical and electrical properties, particularly the stretching sensitivity of the prepared TPU/NFC@CNTs nanocomposites, were investigated. It was found that the prepared TPU/NFC@CNTs has much better mechanical properties and electrical conductivity compared with those of TPU/CNTs composites. More importantly, a linear change of electrical conductivity as a function of stretching is observed for at least strains up to 300% and a very high sensitivity whose gauge factor close to 50 could be achieved. The excellent stretching sensitivity could be attributed to the unique role of NFC: (1) assisting the dispersion of CNTs, (2) enhancing the interaction between NFC and TPU matrix as due to its amphiphilicity, and (3) increasing the overall aspect ratio of CNTs via connecting many tiny CNTs bundled together along the long axis.
Co-reporter:Hongju Zhou, Hua Deng, Li Zhang, and Qiang Fu
ACS Applied Materials & Interfaces August 30, 2017 Volume 9(Issue 34) pp:29071-29071
Publication Date(Web):August 9, 2017
DOI:10.1021/acsami.7b07947
The low efficiency of thermal conductive filler is an unresolved issue in the area of thermal conductive polymer composites. Although it is known that minimizing phonon or electron interfacial scattering is the key for achieving high thermal conductivity, the enhancement is generally limited by preparation methods that can yield the ideal morphology and interfaces. Herein, low temperature expandable graphite (LTEG) is added into a commercial impact modifier (Elvaloy4170), which is then coated onto poly(butylene terephthalate) (PBT) particles with various sizes at millimeter scale between their melting temperatures. Thus, macroscopic segregated filler networks with several considerations are constructed: high LTEG loading leads to a short distance between fillers and a robust filler network; continuous Elvaloy-LTEG phase leads to a continuous filler network; and good interaction among filler and matrix leads to good interfacial interaction. More importantly, the rather large size of PBT particles provides the filler networks with low specific interfacial area, which minimizes the interfacial scattering of phonons or electrons. Relative to homogeneous composites with an identical composition, the thermal conductivity is enhanced from 6.2 to 17.8 W/mK. Such an enhancement span is the highest compared with results reported in the literature. Due to possible “shortcut” behavior, much higher effectiveness can be achieved for the current system than found in literature results when the Elvaloy-LTEG phase is considered as filler, with the effectiveness even exceeding the upper limit of theoretical calculation for highly loaded Elvaloy-LTEG phase with relatively large PBT particle sizes. This could provide some guidelines for the fabrication of highly thermal conductive polymer composites as well as multifunctional polymer composites.Keywords: electrical conductivity; EMI shielding ability; polymer composites; segregated structure; thermal conductivity;
Co-reporter:Kai Wu, Chuxin Lei, Rui Huang, Weixing Yang, Songgang Chai, Chengzhen Geng, Feng Chen, and Qiang Fu
ACS Applied Materials & Interfaces 2017 Volume 9(Issue 8) pp:
Publication Date(Web):February 6, 2017
DOI:10.1021/acsami.6b16586
It is still a challenge to fabricate polymer-based composites with excellent thermal conductive property because of the well-known difficulties such as insufficient conductive pathways and inefficient filler–filler contact. To address this issue, a synergistic segregated double network by using two fillers with different dimensions has been designed and prepared by taking graphene nanoplates (GNPs) and multiwalled carbon nanotubes (MWCNT) in polystyrene for example. In this structure, GNPs form the segregated network to largely increase the filler–filler contact areas while MWCNT are embedded within the network to improve the network-density. The segregated network and the randomly dispersed hybrid network by using GNPs and MWCNT together were also prepared for comparison. It was found that the thermal conductivity of segregated double network can achieve almost 1.8-fold as high as that of the randomly dispersed hybrid network, and 2.2-fold as that of the segregated network. Meanwhile, much higher synergistic efficiency (f) of 2 can be obtained, even greater than that of other synergistic systems reported previously. The excellent thermal conductive property and higher f are ascribed to the unique effect of segregated double network: (1) extensive GNPs–GNPs contact areas via overlapped interconnections within segregated GNPs network; (2) efficient synergistic effect between MWCNT network and GNPs network based on bridge effect as well as increasing the network-density.Keywords: graphene nanoplates; multiwalled carbon nanotubes; segregated double network; synergy; thermal conductivity;
Co-reporter:Zhenwei Liu;Hongwei Bai;Yuanlin Luo;Qin Zhang
RSC Advances (2011-Present) 2017 vol. 7(Issue 18) pp:11076-11084
Publication Date(Web):2017/02/07
DOI:10.1039/C6RA27401C
Selective localization of conductive nanofillers in one phase of co-continuous polymer blends provides an efficient method to greatly reduce the electrical percolation threshold of conductive polymer composites. However, it is still a big challenge to achieve very low percolation thresholds because the critical content for the complete continuity of the selectively filled phase is generally high. In this contribution, taking poly(L-lactide)/thermoplastic polyurethane/carbon nanotubes (PLLA/TPU/CNTs) composite as an example, we demonstrate a facile and versatile strategy for the fabrication of highly conductive PLLA-based composites with very low percolation threshold as well as excellent stiffness–toughness balance via constructing stereocomplex (SC) crystallites in PLLA melt to effectively tailor the phase transition behavior of the blend matrices. To do this, small amounts of poly(D-lactide) (PDLA) capable of co-crystallizing with the PLLA chains to form SC crystallites were incorporated into the composites by melt mixing at 190 °C. These SC crystallites can serve as physical cross-linking points to significantly increase PLLA melt-viscosity and subsequently induce the formation of co-continuous structure in the PLLA/TPU blend matrix at a much lower content of the CNTs-filled TPU phase. As a result, the obtained composites not only show a dramatically reduced percolation threshold (0.3 wt%) but also exhibit a balanced impact toughness and mechanical strength. Importantly, the strategy to promote the complete continuity of the CNTs-filled phase in blend matrix is low-cost and scalable, opening up a new avenue for the design and engineering of highly conductive PLLA-based composites.
Co-reporter:Yao Jing;Li Zhang;Rui Huang;Dongyu Bai;Hongwei Bai;Qin Zhang
Journal of Materials Chemistry A 2017 vol. 5(Issue 37) pp:19729-19737
Publication Date(Web):2017/09/26
DOI:10.1039/C7TA05379G
Stereocomplex (sc) crystallization between poly(L-lactide) (PLLA) and poly(D-lactide) (PDLA) exhibits great potential for the development of high-performance polylactide (PLA) materials because sc crystallites possess many superior physicomechanical properties compared to homo-crystallites. However, it remains a challenge to fabricate electrospun sc-PLA membranes with sufficient mechanical strength and structural integrity for practical applications due to the weak adhesion between fibers. Herein, we devise a new low-temperature sintering mechanism that leads to substantially improved inter-fiber adhesion and the resultant membrane performance. We find that sintering below the melting temperature of sc crystallites can induce the interdiffusion of PLLA/PDLA chain segments from adjacent sc-PLA fibers across the intersections, which subsequently co-crystallize into new sc crystallites capable of tightly welding these fibers together. As a result, the tensile strength and Young's modulus of the electrospun membranes are significantly enhanced from 0.9 MPa and 23.7 MPa to 11.1 MPa and 546.2 MPa, respectively. Critically, the mechanical enhancement is achieved without changing the original porous structure of the electrospun membranes, which is distinctly different from the destroyed membrane structure obtained by conventional thermal annealing at a temperature near the melting temperature of sc crystallites. We further demonstrate that the sintered membranes have excellent chloroform/water separation ability without being destroyed or even swollen. Our overall findings suggest a highly effective approach to fabricate PLA nanofibrous membranes with superior mechanical strength and unprecedented separation performance through interfacial stereocomplex crystallization.
Co-reporter:Weixing Yang;Zedong Zhao;Kai Wu;Rui Huang;Tianyu Liu;Hong Jiang;Feng Chen
Journal of Materials Chemistry C 2017 vol. 5(Issue 15) pp:3748-3756
Publication Date(Web):2017/04/13
DOI:10.1039/C7TC00400A
With the extensive use of portable and wearable electronic devices, ultrathin electromagnetic interference (EMI) shielding materials with excellent thermal management are increasingly desirable. In this study, ultrathin and highly aligned reduced graphene oxide (RGO)/cellulose nanofiber (CNF) composite films with excellent EMI shielding performance and strong anisotropy of thermal conductivity were fabricated by vacuum-assisted filtration followed by hydroiodic acid (HI) reduction. The obtained 50 wt% RGO/CNF composite films, which are only ≈23 μm in thickness, possess the remarkable electrical conductivity of ≈4057.3 S m−1 and outstanding EMI shielding effectiveness (SE) of ≈26.2 dB owning to the uniform dispersion and self-alignment into the layered structure of RGO. In addition, the RGO/CNF composite films with 50 wt% RGO loadings possess high in-plane thermal conductivity (K ≈ 7.3 W m−1 K−1) and, unexpectedly, very low cross-plane thermal conductivity (K⊥ ≈ 0.13 W m−1 K−1), resulting in strong anisotropy of the thermal conductivity (K/K⊥ ≈ 56). Thus, these ultrathin RGO/CNF composite films have great application potential as effective lightweight shielding materials against electromagnetic microwaves and heat, especially in flexible portable electronic devices and wearable devices.
Co-reporter:Wen-jin Yu;Shu-man Xu;Li Zhang 傅强
Chinese Journal of Polymer Science 2017 Volume 35( Issue 9) pp:1132-1142
Publication Date(Web):19 July 2017
DOI:10.1007/s10118-017-1954-1
In this work, completely immiscible polyethylene/polyamide12 (PE/PA12) blends were prepared by high shear extruder. The morphology and mechanical properties of the blends were investigated as a function of rotation speed. It was found that the high shear processing is an effective method to improve the dispersion of the PA12 phase in PE matrix when PA12 contents are 5 wt% and 10 wt%, and the dispersed phase particle size is reduced with the increase of rotation speed from 100 r/min to 500 r/min. However, with further increase of PA12 content to 20 wt%, high shear processing has no effect on the phase morphology of the blends. Accordingly, a largely increased elongation at break and impact strength are observed for PE/PA12/95/5 and PE/PA12/90/10 blends obtained at high rotation speeds but no effect on the property of PE/PA12/80/20. Annealing experiment demonstrated that the obtained phase morphology is not stable thus compatibilizer should be introduced in the future work. This work could provide a guideline for the application of high shear processing in the preparation of polymer blends with huge polarity difference.
Co-reporter:Yi-lan Guo;Run-zhi Zhang;Kai Wu;Feng Chen 陈枫
Chinese Journal of Polymer Science 2017 Volume 35( Issue 12) pp:1497-1507
Publication Date(Web):05 September 2017
DOI:10.1007/s10118-017-1985-7
In this article, hybrid fillers with different dimensions, namely, 2-dimensional (2-D) expanded graphite (EG) and 1-dimensional (1-D) multi-walled carbon nanotubes (CNTs), were added to aromatic nylon MXD6 matrix via melt-blending, to enhance its thermal and electrical conductivity as well as electromagnetic interference shielding effectiveness (EMI SE). For ternary composites of MXD6/EG/CNTs, the electrical conductivity reaches up nine orders of magnitude higher compared to that of the neat MXD6 sample, which turned the polymer-based composites from an insulator to a conductor, and the thermal conductivity has been enhanced by 477% compared with that of neat MXD6 sample. Meanwhile, the EMI SE of ternary composite reaches ~50 dB at the overall filler loading of only 18 wt%. This work can provide guidance for the preparation of polymer composites with excellent thermal and electrical conductivity via using hybrid filler.
Co-reporter:Huili Liu, Hongwei Bai, Dongyu Bai, Zhenwei Liu, Qin Zhang, Qiang Fu
Polymer 2017 Volume 108() pp:38-49
Publication Date(Web):13 January 2017
DOI:10.1016/j.polymer.2016.11.034
•A facile strategy to anchor MWCNTs at the interface of PLLA/EGD blends has been reported.•Many MWCNTs are firmly anchored at the blend interface by SC crystallites.•The SC crystallites can be rapidly formed at the blend interface during melt mixing.•The anchored MWCNTs can remarkably enhance interfacial strength and impact toughness of the blends.•The interfacial localization of MWCNTs facilitates the formation of conductive pathway.Selective localization of nanoparticles at the interface of immiscible polymer blends has been witnessed as an efficient method to improve blend properties and even provide some added functionalities. Nevertheless, it is still a great challenge to achieve thermodynamically stable interface-localization of the nanoparticles mainly due to their low interfacial stabilities as well as high transfer speeds between the blend phases, especially for those with high aspect ratios. In this work, taking poly(l-lactide)/poly(d-lactide) grafted ethylene-acrylic ester copolymer/multi-walled carbon nanotubes (PLLA/EGD/MWCNTs) ternary composite as an example, we describe a new and facile strategy to address this challenge via anchoring high-aspect-ratio MWCNTs at the interface of PLLA/EGD blends using interface-localized stereocomplex (SC) crystallites as anchoring agents. During melt mixing of EGD with PLLA/MWCNTs mixture, such SC crystallites can be rapidly formed at the blend interface to prevent MWCNTs transferring from the thermodynamically unfavorable PLLA matrix into favorable EGD phase as physical barriers, and meanwhile some of these transferring MWCNTs could serve as nucleating agents to induce SC crystallization on their surfaces. As a result, many MWCNTs are firmly anchored at the blend interface by these SC crystallites. The anchored MWCNTs can not only function as effective interfacial enhancers to remarkably enhance interfacial strength and resulting impact toughness of PLLA/EGD blends but also enable the formation of electrical conductive pathway in the network-like PLLA/EGD blends at a much lower percolation threshold. This wok could offer a promising opportunity for preparing high-performance and multifunctional PLLA-based composites through controlling particle localization at the interface of immiscible PLLA blends with the aid of SC crystallization.
Co-reporter:Chengzhen Geng, Hongwei Bai, Qiang Fu, Feng Luo
Polymer Testing 2017 Volume 60(Volume 60) pp:
Publication Date(Web):1 July 2017
DOI:10.1016/j.polymertesting.2017.03.019
Polypropylene (PP) was compounded with β-nucleating agent and injection-molded at 180 °C or 220 °C. The samples were subsequently treated by supercritical carbon dioxide (scCO2) at different temperatures. Results show that processing temperature and scCO2 treatment could strongly influence the tensile and impact properties of β-nucleated PP. In particular, the sample processed at 220 °C and treated at 120 °C exhibit much enhanced impact strength (4.8 times that of its untreated counterpart). FTIR, WAXD, SEM and DMA were performed to explore the effects of processing temperature and scCO2 treatment on structure of the samples. Deformation-induced plastic flow and micro-voids were also evaluated to construct structure-property relations. It was found that the influence of processing temperature on mechanical properties is mainly associated with the β-form content and β-crystalline morphology, while the structural changes in the crystalline lamellar scale may be responsible for the toughening effect of scCO2 treatment.
Co-reporter:Tianyu Liu, Fangyu Xiang, Xiaodong Qi, Weixing Yang, Rui Huang, Qiang Fu
Polymer 2017 Volume 126(Volume 126) pp:
Publication Date(Web):22 September 2017
DOI:10.1016/j.polymer.2017.08.047
•The in-situ formation of polylactide stereocomplex crystallites (sc-PLA) in the PMMA matrix has been achieved by simple melt-blending.•The morphology and dispersion of sc-PLA micro-particles have been systematically studied.•The sc-PLA micro-particles could largely enhance the mechanical property and shape memory performance of PMMA without the sacrifice of its excellent optical transparency.Optically transparent poly(methyl methacrylate) (PMMA)-based blends with significantly enhanced mechanical and shape memory properties have been successfully prepared via in-situ formation of micro-scale polylactide stereocomplex crystallites (sc-PLA) in the PMMA matrix in this work. To achieve this goal, a certain content of poly(l-lactide) (PLLA) was firstly melt-blended with PMMA to obtain completely miscible PMMA/PLLA blends, and then an equimolar poly(d-lactide) (PDLA) was incorporated into the blends, giving rise to the in-situ formation of sc-PLA between PLLA and PDLA. In this way, the micro-scale sc-PLA particles were successfully fabricated and homogeneously dispersed in the PMMA matrix. Consequently, these resultant PMMA/sc-PLA blends possess extremely superior optical transparency, even when the content of sc-PLA reaches up to 12 wt%. A further increase in the content of sc-PLA would lead to the formation of sc-PLA network and aggregation, resulting in the deterioration of optical transparency. Moreover, the incorporation of sc-PLA micro-particles significantly enhances the mechanical property of PMMA and the maximum (≈103 MPa) of these blends demonstrates 50% increase than that (≈70 MPa) of PMMA. More importantly, it has been found that the shape recovery performance of PMMA could be effectively improved by the incorporation of sc-PLA. The optimal shape recovery ratio (86%) and high shape fixing ratio (almost 100%) can be obtained for the PMMA/sc12 blend which exhibits excellent optical transparency. It is reasonable to believe that these optically transparent blends with largely enhanced mechanical and shape memory properties possess great application potential in advanced shape memory fields.Optically transparent poly(methyl methacrylate) (PMMA)-based blends with significantly enhanced mechanical and shape memory properties have been successfully prepared via in-situ formation of micro-scale polylactide stereocomplex crystallites in the PMMA matrix in this work.Download high-res image (278KB)Download full-size image
Co-reporter:Guopeng Sui, Wenjin Yu, Qin Zhang, Feng Chen, Qiang Fu
Polymer 2017 Volume 123(Volume 123) pp:
Publication Date(Web):11 August 2017
DOI:10.1016/j.polymer.2017.07.007
•The relationship between rotation speed and the average MWCNT length was systematically studied.•The high-shear processing is an efficient method to achieve excellent dispersion of MWCNT in olefin block copolymer.•The optimal balance between the dispersion and shortening of MWCNTs was obtained at the rotation speed of 500 rpm.Melt blending is a promising and practical method to prepare electrical conductive polymer composites containing multiwalled carbon nanotubes (MWCNTs). The key is to achieve a good dispersion of MWCNTs in polymer matrix. In this study, olefin block copolymer (OBC)/MWCNTs composites were prepared using co-rotating twin-screw extruder with high rotation speed and the influence of screw rotation speed on the dispersion, shortening of MWCNTs and the macro-properties of composites was systematically investigated. It was found that the entangled agglomerates of MWCNTs could be easily destroyed by using high rotation speed and an improved dispersion of MWCNTs was observed as increasing of rotation speed from 50 to 500 rpm. However, with further increasing of rotation speed from 500 to 1000 rpm, no better dispersion was evidenced but a reduction of nanotubes length was detected. As a result, the best electrical conductivity and mechanical properties of OBC/MWCNTs composites were achieved via using the rotation speed of 500 rpm. And the electrical percolation threshold obtained was about 1.5 wt%. This study provides significant guidance for large-scale preparation of conductive composites materials by using co-rotating twin-screw extruder with high rotation speed.Download high-res image (162KB)Download full-size image
Co-reporter:Yongsheng Zhao, Yanling Zhu, Guopeng Sui, Feng Chen, Qiang Fu
Polymer 2017 Volume 109() pp:137-145
Publication Date(Web):27 January 2017
DOI:10.1016/j.polymer.2016.12.025
•OBC can be fully miscible with small amount of UHMWPE while phase separation occurs when the content of UHMWPE is large.•Small addition of UHMWPE favors increased tie-effect.•Increased tie-effect is helpful to the elasticity retaining as well as strength enhancement.•Large addition of UHMWPE gives rise to phase separation and mixed shish-kebabs, leading to elastomer-to-plastic transition.In this study, the crystalline morphology and mechanical property of Olefin Block Copolymer (OBC) were tailored by adding a small amount (up to 10 wt%) of ultrahigh molecular weight polyethylene (UHMWPE). To do this, OBC and UHMWPE was solution blended first and then subjected to compression molding or injection molding, respectively. It was found that a small quantity of UHMWPE (0.5 wt%, 1 wt%) can be fully mixed with OBC, while phase separation occurs when UHMWPE content is higher than 2.5 wt%, as suggested by SEM and DSC results. For compression molded samples, an obvious increase of Young's modulus from 12 MPa to 22 MPa while maintaining the good elasticity of OBC was observed as the content of UHMWPE is less than 2.5 wt% (in the phase miscible range). With further increasing of UHMWPE content to 10 wt%, only slightly increased Young's modulus is seen. Thus the miscibility between OBC and UHMWPE plays an important role in determining the mechanical property for compression molded samples. However, a continuous increase of Young's modulus was observed with the increase of UHMWPE content for samples obtained via injection molding, with a slight increase (from 23 MPa to 40 MPa) as the content of UHMWPE is less than 2.5 wt%, while with a large increase (from 40 MPa to 156 MPa) as the content of UHMWPE increases from 2.5 wt% to 10 wt%, accompanied with a greatly decrease of elongation (from 1100% to 50%). Even elastomer-to-plastic transition takes place when the content of UHMWPE is large (5 wt%, 10 wt%). Structural analysis of injection-molded samples shows that shish-kebab-like structures can be successfully induced as addition of UHMWPE along with gradually increased crystal orientation. It was interesting to find that small-addition of UHMWPE favors increased tie-effect due to the miscibility between OBC and UHMWPE, which is helpful to the elasticity retaining as well as strength enhancement, while large-addition of UHMWPE gives rise to phase separation and mixed shish-kebabs (OBC/UHMWPE hybrid shish-kebabs and UHMWPE homo-shish-kebabs), leading to elastomer-to-plastic transition.
Co-reporter:Hao Xiu, Xiaodong Qi, Hongwei Bai, Qin Zhang, Qiang Fu
Polymer Degradation and Stability 2017 Volume 143(Volume 143) pp:
Publication Date(Web):1 September 2017
DOI:10.1016/j.polymdegradstab.2017.07.002
Adding titanium dioxide (TiO2) into Polylactide (PLA) matrix is an efficient way to improve the UV-resistance of PLA for outdoor applications. In this work, soft poly(ester)urethane elastomer was used to tailor the dispersion and distribution of TiO2 nanoparticles and improve the toughness of PLA as well. It was observed that TiO2 nanoparticels are selectively located at the interface between PU dispersed phase and PLA matrix to form a so called soft core-rigid shell structure. Interestingly, the addition of PU gives a significant rise to not only toughness, but also UV-resistance of PLA/TiO2 composites. According to Fourier transform infrared spectroscopy (FTIR), the anhydride as the main photoproducts was confirmed for all the prepared samples, including PLA, PLA/PU blends, PLA/TiO2 and (PLA/TiO2)PU nanocomposites, which indicates that the addition of PU or/and TiO2 does not alter the photooxidation chemical mechanism of PLA. The enhancement of anti-UV performance is mainly ascribed to good UV-absorption ability of PU and TiO2 nanoparticels.
Co-reporter:Wenjing Ji, Hua Deng, Qiang Fu
Composites Science and Technology 2017 Volume 151(Volume 151) pp:
Publication Date(Web):20 October 2017
DOI:10.1016/j.compscitech.2017.07.022
High dielectric constant filler is often used to improve the dielectric properties of polymer. Most studies are focused on the uniform filler dispersion and interface between filler and polymer. Herein, multi-layered films containing BaTiO3 and multi-wall carbon nanotubes (MWCNTs) as fillers, with different filler distributions were designed and prepared, including alternating distribution of layers with/without filler; core-shell distribution with filler concentrated at core or shell; and uniform distribution. The overall filler content in these films was kept constant. These films have almost the same dielectric loss. Interestingly, it was noted that the largest dielectric constant is achieved for sample with filler concentrated at the shell (around 50% higher than the rest at low frequency). Interfacial polarization and filler localization are thought to play important role. However, classic Series model does not take these issues into account. To understand this, a modified Series model was proposed to calculate the dielectric constant of multi-layered films by considering these issues. Such equation is much more accurate at describing experimental results from current study as well as some published literature than classic Series model. Our work demonstrates the importance of hierarchical structure in polymer composites for dielectric property and heterogeneous distribution of filler could be much better than uniform distribution.
Co-reporter:Kai Wu, Yuanwei Li, Rui Huang, Songgang Chai, Feng Chen, Qiang Fu
Composites Science and Technology 2017 Volume 151(Volume 151) pp:
Publication Date(Web):20 October 2017
DOI:10.1016/j.compscitech.2017.07.014
With the rapid development of high performance capacitors for energy storage, materials with both giant dielectric constant and low dielectric loss are urgently needed. Adding conductive filler could largely enhance the dielectric constant of polymer matrix but also greatly increase the dielectric loss. In this study, we provide a new strategy by using hybrid fillers to construct a segregated double network, where conductive multi-walled carbon nanotubes (MWCNT) network is wrapped by insulating hexagonal boron nitride (h-BN) network to destroy the continuity of embedded MWCNT network. To do this, pre-fabricated micron-sized PS/MWCNT particles were completely coated by h-BN through π-π interaction. As a result, the MWCNT network inside h-BN network provides good conductivity while h-BN network provides the isolation effect but do not increase the distance between two adjacent MWCNT agglomerations, which together can maintain the high dielectric constant and decrease the dielectric loss. Therefore, a high dielectric constant of 123 is achieved while a relatively low dielectric loss is also kept as 0.36. More importantly, this special structure of segregated double network also leads to obviously enhanced thermal conductivity which is 2.23-fold of that of the composites with randomly dispersed hybrid fillers. This high thermal conductivity is ascribed to the high synergistic efficiency between segregated h-BN network and dense MWCNT network. We believe that these good comprehensive performances promise this structure to offer a unique and effective way to prepare high-performance dielectric materials with not only high dielectric constant and low dielectric loss, but also good capability of heat dissipation.
Co-reporter:Junjin Che, Kai Wu, Yunjie Lin, Ke Wang, Qiang Fu
Composites Part A: Applied Science and Manufacturing 2017 Volume 99(Volume 99) pp:
Publication Date(Web):1 August 2017
DOI:10.1016/j.compositesa.2017.04.001
Utilizing the synergistic effect of various fillers is an efficient strategy to enhance the thermal conductivity of polymer composites, in which the key is to modulate their dispersion and network formation in polymer matrix. In this work, expanded graphite (EG) was individually added into high density polyethylene (HDPE) to fabricate first the binary composites through melt blending. The electrical conductivity of the prepared composites was measured to determine the percolation threshold for HDPE/EG composites. Then HDPE/EG composites with three compositions, representing below percolation, just percolation and above percolation, respectively, were chosen as matrix and melt mixed with carbon nanotubes (CNTs) to make HDPE/EG/CNTs ternary composites. It was found that adding CNTs results in a linear increase of thermal conductivity for HDPE/EG composites with composition below percolation, along the line by adding the same amount of EG. While a jump of thermal conductivity was observed by adding CNTs for HDPE/EG composites with composition just and above percolation. The electrical conductivity and rheology property were measured and SEM experiment was carried out to explore the filler dispersion and their network formation in HDPE matrix. All the results suggested a possible location CNTs in EG filler network for HDPE/EG composites with composition just and above percolation. Thus the formation of CNTs network within EG network is attributed to the main reason for the largely enhanced thermal property. This work endows a new enlightenment to fabricate the composites with a great thermal conductivity.
Co-reporter:Rui Huang;Gang Wang;Shuo Guo;Ke Wang
Physical Chemistry Chemical Physics 2017 vol. 19(Issue 40) pp:27828-27838
Publication Date(Web):2017/10/18
DOI:10.1039/C7CP04741J
Among all the polymorphs of poly(vinylidene fluoride) (PVDF), the polar γ-form possesses the highest melting point and electrical breakdown strength as well as the strongest solvent and irradiation resistance, which are beneficial for the durability of PVDF products. Since the γ-form is neither kinetically favorable nor the most thermodynamically stable, it is still difficult to attain the exclusive γ-polymorph, particularly in the case of neat PVDF. In this study, the melt isothermal crystallization of PVDF films was carried out between two KBr wafers. Owing to the characteristics of KBr wafer, including no IR absorbance and high optical transmittance, the crystallographic features originating from the KBr substrate can be conveniently elucidated through the in situ inspected techniques of FTIR and PLM. The KBr wafers significantly accelerated the crystallization kinetics of α-crystals, and then readily triggered the solid-state α- to γ-transformation of the pre-formed α-spherulites, resulting in a 10 μm-thick, neat PVDF film with an absolute crystallinity of 35% and a relative γ fraction as high as 94%. When the film thickness was increased to 40 μm, the crystallization rate of the α-form was still rapid, but the solid-state transformation was not appreciable. These interesting crystallographic phenomena are attributed to the existence of ion–dipole interaction between the –CF2 or –CH2 of PVDF chains and the surface of KBr wafer. Unlike most traditional substrate-dominated crystallizations that prevail in a surface epitaxy manner, in which the target films are of ultra-thin thickness (of the order of 10 nm), the ion–dipole interaction promotes the effective thickness to a ten micron level, which enables its production and application at scalable level. Moreover, the triggering of α- to γ-transformation via external fields could be an alternative for achieving the γ-dominant PVDF products, particularly when the introduction of external additives is prohibited.
Co-reporter:Wei Xue;Cong Lv;Yao Jing;Feng Chen 陈枫 傅强
Chinese Journal of Polymer Science 2017 Volume 35( Issue 8) pp:992-1000
Publication Date(Web):25 June 2017
DOI:10.1007/s10118-017-1937-2
In this work, the effect of dioctadecyl dimethyl ammonium chloride (DDAC, a kind of alkyl ammonium salt) on polar β phase content and the diameter of electrospun PVDF nanofibers was investigated for the first time. Our experimental results show that the diameter of the electrospun PVDF nanofiber could be largely reduced and the content of polar β phase also become dominant immediately by just adding a little amount of DDAC. When the mass fraction of DDAC reached 4%, the content of polar β phase increased by about 39.1% compared with PVDF nanofibers without DDAC. Besides, the crystallinity of PVDF nanofibers also increased with the addition of DDAC. Based on the results, the possible mechanism of cooperative effect between electrospinning and DDAC on fiber diameter and formation of β phase in PVDF was discussed.
Co-reporter:Zhenwei Liu, Yuanlin Luo, Hongwei Bai, Qin Zhang, and Qiang Fu
ACS Sustainable Chemistry & Engineering 2016 Volume 4(Issue 1) pp:111
Publication Date(Web):November 17, 2015
DOI:10.1021/acssuschemeng.5b00816
As an eco-friendly polymer with tremendous potential to replace traditional petroleum-based and nonbiodegradable polymers, the current use of poly(l-lactide) (PLLA) in large-scale commercial applications still faces some barriers mostly associated with its inherent brittleness and poor heat resistance. In this work, we propose a novel and facile strategy to simultaneously address these obstacles by introducing small amounts of poly(d-lactide) (PDLA) into thermoplastic polyurethane (TPU) toughened PLLA blends through melt-blending. The results manifest that the introduced PDLA chains can readily interact with PLLA matrix chains and rapidly cocrystallize into stereocomplex (sc) crystallites capable of acting as an efficient rheology modifier to dramatically improve melt viscoelasticity of the PLLA matrix and subsequently induce the morphological change of the dispersed TPU phase from a typical sea–island structure to a unique networklike structure, thus endowing PLLA/TPU/PDLA blends with remarkably improved impact toughness as compared to its PLLA/TPU counterparts. Moreover, the formed sc crystallites can also serve as a highly efficient nucleating agents to substantially accelerate matrix crystallization, which makes it possible to prepare PLLA/TPU blends with a highly crystalline matrix using conventional injection molding technology. More interestingly, the improvement in the matrix crystallization can significantly enhance the heat resistance of the blends without evidently weakening the contribution of the tailored phase morphology to the toughness improvement. These inspiring findings suggest that the construction of sc crystallites in the matrix could be a promising avenue toward fabricating high-performance PLLA/elastomer blends via simultaneously tuning phase morphology and matrix crystallization.Keywords: Heat resistance; poly(l-Lactide); Polyurethane; Stereocomplex; Toughness;
Co-reporter:Huixian zhang, Hongwei Bai, Zhenwei Liu, Qin Zhang, and Qiang Fu
ACS Sustainable Chemistry & Engineering 2016 Volume 4(Issue 7) pp:3939
Publication Date(Web):May 31, 2016
DOI:10.1021/acssuschemeng.6b00784
As a sustainable alternative to conventional petrochemical-based polymers, biobased and biodegradable poly(l-lactide) (PLLA) exhibits tremendous application potential in the textile industry due to its attractive elastic recovery, moisture regain, and flammability. However, the commercial adoption of PLLA textile fibers still faces some hurdles mainly associated with their poor heat resistance (i.e., high thermal shrinkage or low dimensional stability) because the low crystallization rate makes PLLA difficult to crystallize during melt spinning. Herein, we report a simple but robust strategy to address this hurdle via simultaneously manipulating crystallinity and lamellae orientation with the aid of a highly active nucleating agent (NA) that can be completely dissolved in PLLA melt and reorganize into fine fibrils upon cooling. By taking full advantage of strong elongational flow field involved in the melt spinning, the NA fibrils with high nucleation efficiency on PLLA crystallization tend to align along the flow direction and subsequently serve as nucleation templates to induce the growth of kebab-like PLLA lamellae perpendicular to their long axis, finally forming large amounts of highly orientated crystal structure in melt-spun PLLA fibers. In this way, the crystallization manipulation imparts the PLLA fibers with an impressive combination of superior mechanical strength and heat resistance. Compared with neat PLLA fiber, a prominent increase of 78% in tensile strength and a substantial decline of 1069% in boiling water shrinkage are achieved in the fiber nucleated with 0.3 wt % NA. This work could open up an avenue toward the design and development of high-performance PLLA fibers by using fibrillar nucleating agent as a nucleation template to tailor effectively crystallization in the melt spinning process.Keywords: Crystallization; Fiber; Heat resistance; Nucleating agent; Poly(l-lactide)
Co-reporter:Kai Wu, Chuxin Lei, Weixing Yang, Songgang Chai, Feng Chen, Qiang Fu
Composites Science and Technology 2016 Volume 134() pp:191-200
Publication Date(Web):6 October 2016
DOI:10.1016/j.compscitech.2016.08.015
Adding conductive filler is an effective way to enhance the dielectric constant while usually also increases the dielectric loss of polymer. In this study, we demonstrated that polymer composites with much improved dielectric constant while maintaining ultra-low dielectric loss could be achieved via using hybrid filler and controlling the dispersion of conductive filler in polymer matrix. To do this, the graphene oxide was designed to be immobilized on the surface of large-sized insulating hexagonal boron nitride (h-BN) via electrostatic self-assembly, and afterwards introducing this hybrid filler into epoxy accompanied with chemical reduction. In this case, since the reduced graphene oxide (rGO) sheets were fixed on the surface of h-BN, rGO sheets were well separated from each other even at high loading. Hence not only significantly enhanced dielectric constant was observed, but also a very low dielectric loss comparable to that of neat epoxy was achieved. This low dielectric loss was believed to be ascribed to both embedded insulating network of h-BN to inhibit the mobility of charge carrier and well-separated rGO sheets via immobilization. In addition to obviously improved dielectric properties, the nanocomposites also exhibited good thermal conductivity. We believe that this special structure will provide a new thought for fabricating dielectric materials with much enhanced dielectric constant as well as well-suppressed dielectric loss.
Co-reporter:Shuman Xu, Wenjin Yu, Xuelin Yao, Qin Zhang, Qiang Fu
Composites Science and Technology 2016 Volume 131() pp:67-76
Publication Date(Web):2 August 2016
DOI:10.1016/j.compscitech.2016.05.014
In this study, nano-fibrillated cellulose (NFC) was used to stabilize the dispersion of chemical reduced graphene oxide (rGO) in aqueous system. Owing to the hydrophobic interactions between the rGO sheets and specific crystalline faces (hydrophobic (200) planes) of NFC as well as electrostatic repulsion between the NFC, a homogenous dispersion of NFC/rGO in water was obtained with good stability. Then the prepared NFC/rGO solution was simultaneously merged into water soluble polyvinyl alcohol (PVA) to obtain PVA/NFC/rGO composite freestanding films via a casting method. It was found that the conductivity of the composite films changed rapidly as changing of relative humidity (RH) and exhibited a good repeatability between RH at 50%–70%. Compared to PVA/rGO film without NFC, PVA/NFC/rGO film exhibited higher conductivity, sensitivity as well as faster response (lower hysteresis). Thus the prepared PVA/NFC/rGO films could serve as an effect humidity sensor. It was suggested that NFC played several roles in the composite films: (1) as compatibilizer to enhance the dispersion of rGO in PVA matrix, (2) as a bridge to enhance the load transfer and humidity transfer between PVA and rGO, and (3) as water absorber to enhance the sensitivity of humidity.
Co-reporter:Hao Xiu, Xiaodong Qi, Zhenwei Liu, Yan Zhou, Hongwei Bai, Qin Zhang, Qiang Fu
Composites Science and Technology 2016 Volume 127() pp:54-61
Publication Date(Web):28 April 2016
DOI:10.1016/j.compscitech.2016.02.025
Bio-degradable polylactide (PLA) based composites has attracted much attention both in academic research and industrial applications in recent decades due to the increasing environmental concerns. In this work, we tried to obtain PLA based composites with good stiffness-toughness balanced properties by adjusting carbon fiber (CF) network in polylactide (PLA) matrix via adding a small amount of soft poly(ether)urethane (PU). It was interesting to find that PU could serve as “solder” to weld CF into a more perfect network due to the fact that PU has stronger interaction with CF as compared with PLA and improve the interface interaction between CF and PLA meanwhile. The self-weld CF network structure was confirmed by SEM characterizations, rheology and conductivity tests. More importantly, the formation of self-weld network structure constructed by both stiff CF and ductile PU elastomer can simultaneously improve tensile strength, impact toughness and even electrical conductivity of PLA. This inspiring result demonstrates that the addition of soft elastomer which has a strong interaction with fiber into fiber-reinforced polymers could be a universal platform to improve the performance of polymer composites via tuning fibers network and the interfacial interaction between fibers and polymer matrix.
Co-reporter:Xiaodong Qi, Peng Dong, Zhenwei Liu, Tianyu Liu, Qiang Fu
Composites Science and Technology 2016 Volume 125() pp:38-46
Publication Date(Web):23 March 2016
DOI:10.1016/j.compscitech.2016.01.023
In this study, we reported a rapid electroactive ternary shape memory polymer (SMP) composites containing multiwalled carbon nanotubes (MWCNTs) and two biodegradable polyesters, namely poly(propylene carbonate) (PPC) and poly(lactic acid) (PLA). To do this, binary polymer blends were firstly prepared, and a good shape memory behavior was observed for blends with co-continuous phase morphology, where by PPC acted as the switching domain due to its good elasticity and PLA acted as the fixing domain due to its high modulus. Then MWCNTs were incorporated into PPC/PLA co-continuous phase (PPC70/PLA30, PPC50/PLA50) by simple melting blending to realize the electroactive shape memory properties. It was found that MWCNTs tended to locate more in the PPC phase than in the PLA phase. The selective localization of MWCNTs not only led to an improvement in the recovery force, but also imparted composites with high electrical conductivity in a low percolation threshold. The composites showed rapid electroactive shape memory behavior, which reached a shape recovery ratio of 97% within 30 s at 30 V. Our work provides a simple approach to utilize the selective localization of MWCNTs in the continuous phase to fabricate rapid electrical actuated SMPs with low MWCNTs loadings, which can be scaled up industrially.
Co-reporter:Zhiqiang Wu, Gang Wang, Mengwei Zhang, Ke Wang and Qiang Fu
Soft Matter 2016 vol. 12(Issue 2) pp:594-601
Publication Date(Web):12 Oct 2015
DOI:10.1039/C5SM02030A
Nucleating agent (NA) species with solubility and self-assembly abilities can readily and effectively manipulate the crystalline morphology of semicrystalline polymers through the construction of heterogeneous frameworks prior to the primary crystallization of basal resins. However, the solubility of NA species is difficult to assess by the current traditional methods. In this study, gradient temperature field (g-T field) was utilized for the first time to ascertain the dissolution and self-assembly behaviors of β-NA in the melts of isotactic polypropylene (iPP). The g-T field technique can facilely assess the soluble behavior of β-NA by determining the transformation between several NA frameworks, namely the needle-, flower- and dendrite-like supramolecular structures. Clarifying the soluble behavior of β-NA is of great significance to guide the formation of various crystalline frameworks under the homo-temperature fields and control the resultant crystalline morphology of β-modified iPP. Some interesting findings are summarized as follows: (1) an in situ observation under the g-T field clearly indicates the sequential occurrence of various nucleation and crystallization events in the same observed window, and proves the migration of well molten β-NA, (2) the exact correlation between Tf and framework type reveals that an abrupt transformation (over the narrow temperature range of 1 °C) occurred between needle-like and dendrite-like frameworks, (3) the primary crystallization of iPP is strongly dependent on the construction mode of the β-NA framework.
Co-reporter:Sha Deng, Rui Huang, Mi Zhou, Feng Chen, Qiang Fu
Carbohydrate Polymers 2016 Volume 154() pp:129-138
Publication Date(Web):10 December 2016
DOI:10.1016/j.carbpol.2016.07.101
•Exfoliation and acylation of microfibrillated cellulose (MFC) was realized.•Modified MFC films showed largely enhanced tensile strength and toughness.•Excellent water resistance and water vapor permeability were achieved.•Optical performance of the modified films was also improved.•We provide an efficient and easily industrialized method for MFC modification.Cellulose films with excellent mechanical strength are of interest to many researchers, but unfortunately they often lack the ductility and water resistance. This work demonstrates an efficient and easily industrialized method for hydrophobic cellulose films made of modified microfibrillated cellulose (MFC). Prior to film fabrication, the simultaneous exfoliation and acylation of MFC was achieved through the synergetic effect of mechanical and chemical actions generated from ball milling in the presence of hexanoyl chloride. Largely enhanced tensile strength and elongation at break have been achieved (4.98 MPa, 4.37% for original MFC films, 140 MPa, 21.3% for modified ones). Due to hydrophobicity and compact structure, modified films show excellent water resistance and decreased water vapor permeability. Moreover, optical performance of modified films is also improved compared with the original MFC films. Our work can largely expand the application of this biodegradable resource and ultimately reduce the need for petroleum-based plastics.
Co-reporter:Xiaodong Qi, Mengfan Jing, Zhenwei Liu, Peng Dong, Tianyu Liu and Qiang Fu
RSC Advances 2016 vol. 6(Issue 9) pp:7560-7567
Publication Date(Web):14 Jan 2016
DOI:10.1039/C5RA22215J
A novel biodegradable polymer-based composite with excellent dual-responsive shape memory properties based on poly(propylene carbonate) (PPC)/microfibrillated cellulose (MFC) was prepared. MFC was modified by a one-step mechanical–chemical approach involving ball milling and an esterification reaction to improve its dispersion. The shape memory properties of PPC/MFC-BR composites and PPC/unmodified MFC composites were compared, and the former showed better shape memory properties due to the uniform dispersion of MFC-BR which ensured a higher fraction of the interfacial zone than unmodified MFC. Here, MFC-BR fibers act as multifunctional cross-links, reinforcing fillers, and relaxation retarders. In addition, the composites with a MFC-BR content of 5–10 wt% showed a good shape memory effect upon exposure to water at 30 °C due to the hydrophilicity of MFC-BR. The mechanism was mainly ascribed to water molecules destroying the hydrogen bonding at the polymer–filler interfaces, which reduced the glass transition temperature and increased the flexibility of the polymer chains. Our work provides a composite approach to tune the shape memory behavior of polymer composites and may contribute to the application of PPC in the smart materials field.
Co-reporter:Xiaoyu Li, Hua Deng, Qin Zhang, Feng Chen and Qiang Fu
RSC Advances 2016 vol. 6(Issue 30) pp:24843-24852
Publication Date(Web):25 Feb 2016
DOI:10.1039/C5RA28118K
The dynamic percolation behavior of conductive fillers in conductive polymer composites (CPCs) has drawn wide interest due to its crucial influence on the final properties. It is thought that the viscosity of the neat polymer, filler–polymer interaction and entanglement in the filler network are crucial issues. Meanwhile, the structure and related characteristics of the filler is an important parameter for determining filler properties and various functionalities. However, their influence on the filler dynamic self-assembly process in a polymer matrix has been barely investigated. Herein, three types of carbon black (CB) with different dibutyl phthalate (DBP) absorption have been used to study the electrical percolation behavior in thermoplastic polyurethane with methods including in situ electrical measurement during isothermal annealing, scanning electron microscopy (SEM), and rheological study as well as theoretical analysis. It is observed that a higher DBP value leads to a lower percolation threshold. During dynamic percolation, the activation energy increases almost linearly with DBP absorption. It is thought that the more stable pre-formed conductive networks for CB with more DBP are responsible. Thus, the driving force for the self-assembly process is lower for CB with more DBP. This study provides new insight for the dynamic self-assembly process of a functional filler in a polymer matrix.
Co-reporter:Jia Dai, Hongwei Bai, Zhenwei Liu, Liang Chen, Qin Zhang and Qiang Fu
RSC Advances 2016 vol. 6(Issue 21) pp:17008-17015
Publication Date(Web):03 Feb 2016
DOI:10.1039/C6RA00051G
Despite its attractiveness as an “green” substitute for conventional petroleum-based polymers, the current application of plant-derived biodegradable poly(L-lactide) (PLLA) in many fields has been greatly limited by its inherent brittleness and poor heat resistance. Herein, taking thermoplastic polyurethane (TPU) toughened PLLA as an example, we report a facile and promising strategy for the fabrication of super-toughened and heat-resistant PLLA/elastomer blends by incorporating small amounts (e.g., 2.5 wt%) of poly(D-lactide) (PDLA) into the blends through melt-blending and subsequent injection molding. The incorporated PDLA chains can readily collaborate with neighboring PLLA matrix chains during the melt-blending process to co-crystallize into stereocomplex (sc) crystallites in the PLLA matrix of the blend melts. Thus, these sc crystallites can behave as a highly efficient nucleating agent to significantly accelerate matrix crystallization, allowing for the preparation of PLLA blends with a highly crystallized PLLA matrix using practical injection molding. The highly crystallized matrix can provide the PLLA/TPU blends with dramatically improved impact toughness and heat resistance as compared with the amorphous one. Meanwhile, the role of these sc crystallites as a rheology modifier to induce the unexpected morphological change from the dispersed TPU phase from the sea-island structure to the unique network-like structure with a much higher toughening efficiency is also observed.
Co-reporter:Di Han, Qin Zhang, Feng Chen and Qiang Fu
RSC Advances 2016 vol. 6(Issue 23) pp:18924-18928
Publication Date(Web):05 Feb 2016
DOI:10.1039/C6RA00218H
Herein, we report a novel strategy to use Janus polyhedral oligomeric silsesquioxane (POSS)–[60]fullerene (C60) (JPC) giant molecules as compatibilizer for immiscible polystyrene (PS)/polymethyl methacrylate (PMMA) blends. It was found that the domain sizes of the dispersed PMMA phase decrease in PS matrix, and tensile strength and elongation of PS/PMMA blends were largely enhanced by adding a small amount of JPC. More importantly, both interfacial tension analyses and elemental Si distribution in the blends suggest a possible location of the JPC at the PS/PMMA interfaces. Our studies provide not only a new idea for the compatibilization of polymer blends, but also for precisely controlling the positions of nanoparticles in a polymer matrix, which is also of great importance for the preparation of polymer nanocomposites with high-performance and excellent functionality.
Co-reporter:Tiannan Zhou, Xiaodong Qi, Hongwei Bai and Qiang Fu
RSC Advances 2016 vol. 6(Issue 41) pp:34153-34158
Publication Date(Web):30 Mar 2016
DOI:10.1039/C6RA02225A
How reduced graphene oxide (rGO) and graphene oxide (GO) affect the performance of chitosan (CS) nanocomposites is discussed in this paper. A special two-step reduction method was used to prepare the CS–rGO nanocomposite films, firstly, the CS–GO nanocomposite films were prepared by the solution casting method, and secondly, the prepared CS–GO films were immersed into a reducing agent aqueous solution in which the reducing agents could diffuse onto the surface of the GO sheets and then reduce them. So this method could avoid the phenomena of aggregation, morphology change and rearrangement of the GO sheets, which would happen if they are directly reduced in the CS–GO solution with or without a surfactant. The results show that the loading of the two kinds of fillers can enhance the tensile strength of the nanocomposites, but the mechanism is different, one reason is due to the strong interfacial interaction between GO and CS, and another one may be due to the high mechanical strength of rGO and the recrystallization of the CS matrix during the reduction process. This work provides a new way to analyze the interfacial interaction between the filler and CS matrix, and also could be used in other polymer systems to find the essential mechanism of how the filler could affect on the mechanical properties of nanocomposites.
Co-reporter:Sha Deng, Yanlin Zhu, Xiaodong Qi, Wenjing Yu, Feng Chen and Qiang Fu
RSC Advances 2016 vol. 6(Issue 51) pp:45578-45584
Publication Date(Web):04 May 2016
DOI:10.1039/C6RA09521F
In recent decades, great efforts have been devoted to prepare materials with enhanced thermal conductivity due to the growing interest in thermal conductive materials. Herein, we illustrate a facile strategy to improve the thermal conductivity of polyvinylidene fluoride/expanded graphite (PVDF/EG) composites by pre-treatment of EG via ball milling. Before incorporating EG into PVDF via conventional melt processing, EG powders were treated by shear-force-dominated ball milling. In this way, the loose and porous vermicular structure of EG could be effectively destroyed and exfoliated to graphite nanosheets (GNSs). As a result, the PVDF/GNSs composites show improved thermal conductivity owing to their larger specific surface area. With the filler content fixed at 15 wt%, the thermal conductivity of treated PVDF/GNSs composites can reach 1.29 W m−1 K−1, 42.5% higher than that of PVDF/EG (0.90 W m−1 K−1). Moreover, the electromagnetic interference (EMI) shielding property and tensile strength of PVDF/CNSs composites are also remarkably improved. Our work proves to be a simple and easily industrialized method for EG treatment which has great potential for improving the thermal conductivity of polymer composites in lighting devices and electromagnetic shielding applications.
Co-reporter:Guopeng Sui, Yongsheng Zhao, Qin Zhang and Qiang Fu
RSC Advances 2016 vol. 6(Issue 60) pp:54785-54792
Publication Date(Web):02 Jun 2016
DOI:10.1039/C6RA11451B
As a promising substitute for traditional thermoplastic elastomers, olefin block copolymers (OBCs) exhibit a marvelous application potential in many fields. To further improve the mechanical properties of OBCs, in this paper, quaternary ammonium salt cetyltrimethyl ammonium bromide (CTAB) was firstly introduced as a modifier for the non-covalent functionalization of graphene oxide (GO), then the modified GO (CTAB-GO) was used as a reinforcing agent for OBCs. With the incorporation of CTAB, a fine dispersion of GO in organic solvent and later in the OBC matrix have been achieved. As a result, the mechanical performance is largely improved, e.g., the increases of tensile strength, elongation at break and Young's modulus are 30%, 13% and 78%, respectively, with 1.0 wt% CTAB-GO incorporation. It is also observed that CTAB-GO exhibits a stronger nucleation ability on crystallization of OBC than pristine GO, which leads to a higher crystallization temperature and smaller size of crystals.
Co-reporter:Sha Deng, Jinwen Wang, Guiying Zong, Feng Chen, Songgang Chai and Qiang Fu
RSC Advances 2016 vol. 6(Issue 12) pp:10185-10191
Publication Date(Web):18 Jan 2016
DOI:10.1039/C5RA26272K
The thermal conductivity of expanded graphite (EG)/polymer composites is investigated in terms of polymer chain structures. The EG/polyphenylene sulfide (PPS) composite with a backbone of benzene rings shows the continuous highest thermal conductivity and the fastest rate of enhanced ratio at the same content. Then it is followed by EG/syndiotactic polystyrene (sPS) composites with side groups of regularly arranged benzene rings. The last are the EG/amorphous polystyrene (aPS) composites with side groups of randomly arranged benzene rings. Our results show that the chain structures of polymer matrices have a great influence on the interaction and crystallization of EG/polymer composites, which leads to the different thermal behavior. More precisely, the strong π–π interaction between EG and polymer, the nucleation of crystal at the interface of EG/polymer and the relatively rich EG content in the amorphous phase are benefits to the enhancement of thermal conductivity. These factors are proved to be extremely important for the design of high thermally conductive composites in the fields of science and engineering.
Co-reporter:Kai Wu, Linyu Wu, Weixing Yang, Songgang Chai, Feng Chen and Qiang Fu
RSC Advances 2016 vol. 6(Issue 57) pp:51900-51907
Publication Date(Web):23 May 2016
DOI:10.1039/C6RA10129A
It has been demonstrated that introducing another non-conductive particle into conductive filler filled composites could result in a better conductivity due to a volume exclusion effect. It was also reported that combining electrically conductive fillers with different geometric shapes and aspect ratio together could enhance the electrical conductivity due to the synergistic effect. To further explore these two effects on the electrical property enhancement, we firstly encapsulated neat silica (SiO2) with graphene oxide (GO) through electrostatic self-assembly to render SiO2 with surface conductivity. Then neat SiO2 or SiO2@GO together with multi-walled carbon nanotubes (MWCNT) were mixed with polystyrene (PS) to prepare conductive composites. In this way, the volume exclusion effect in the PS/MWCNT/SiO2 system and combined effect of volume exclusion and synergy in the PS/MWCNT/SiO2@rGO system could be investigated and compared. An obvious increased conductivity was observed only in the transition composition region for the PS/MWCNT/SiO2 system compared with the PS/MWCNT system. However, a largely enhanced conductivity was achieved through the composition region for the PS/MWCNT/SiO2@rGO system compared with the PS/MWCNT/SiO2 system and PS/MWCNT, accompanied by great enhancement of the electromagnetic interference (EMI) shielding effectiveness. Given the SEM characterization and rheological properties, we attributed this obvious enhanced electrical property to both a volume exclusion effect and a synergistic effect.
Co-reporter:Hongju Zhou, Hua Deng, Li Zhang, Zhiqiang Wu, Sha Deng, Weixing Yang, Qin Zhang, Feng Chen, Qiang Fu
Composites Part A: Applied Science and Manufacturing 2016 82() pp: 20-33
Publication Date(Web):March 2016
DOI:10.1016/j.compositesa.2015.11.030
The distribution of functional filler is known to have significant influence on various functionalities, yet, not been systematically investigated. Herein, we use a blends system based on PA12/PA6 containing SiC and low-temperature expandable graphite (LTEG) to study it. The effect of filler distribution in such blends on various functionalities including: thermal conductivity, electrical conductivity, and electromagnetic interference (EMI) shielding ability, has been systematically studied. Further study on altering filler distribution with polished PA6-LTEG and PA6-LTEG in different sizes reveals that, polished particle surface results in reduced electrical and thermal conductivity; and smaller particle size leads to enhanced electrical conductivity, thermal conductivity and EMI shielding ability. Finally, theoretical approach on thermal conductivity demonstrates that the system illustrates very effective contribution in thermal conductivity from large PA6-LTEG “filler” comparing to much smaller traditional fillers. Such study could provide a guideline for the processing of functional polymer composites.
Co-reporter:Bowen Yu, Chengzhen Geng, Mi Zhou, Hongwei Bai, Qiang Fu, Bobing He
Composites Part B: Engineering 2016 Volume 92() pp:413-419
Publication Date(Web):1 May 2016
DOI:10.1016/j.compositesb.2016.02.040
•For the first time, the combined effects of elastomer and annealing on the toughness of polypropylene/glass fiber composites were investigated.•The interplay between extrinsic toughening effect of glass fiber and intrinsic toughening effects of elastomer/annealing was discussed.•A synergetic effect between GF extrinsic toughening and annealing-related toughening was demonstrated.•The intrinsic toughening mechanism of elastomer will be suppressed by glass fiber irrespective of the support of annealing.There are principally two mechanisms to improve the impact resistance of polymer-based composites, intrinsic toughening and extrinsic toughening. But the interplay between them is far from being well understood. Here, glass fiber was incorporated into polypropylene to promote extrinsic toughening mechanism, while addition of elastomer and annealing were adopted for intrinsic toughening. In this way, the interaction among glass fiber, elastomer and annealing could be discussed based on various characterizations, and their combined effect on mechanical properties of the composites could be determined. The results show that the intrinsic toughening mechanism of elastomer will be suppressed by glass fiber irrespective of the support of annealing, though annealing could work synergistically with glass fiber to toughen polypropylene. The possible structure-property relations are discussed. This work will provide deeper insight into the toughening behavior of polymer composites and practical guidance for the design of composites with excellent stiffness-toughness balance.
Co-reporter:Yanling Zhu, Yongsheng Zhao, Qiang Fu
Polymer 2016 Volume 103() pp:405-414
Publication Date(Web):26 October 2016
DOI:10.1016/j.polymer.2016.09.023
•The crystalline morphologies transform β-spherulites into large quantity of β-transcrystals (β-TCs) by adding small amounts of EA-UFPR.•The transformation mechanism is related to the hindering effect of EA-UFPR on the self-assembly of β nucleating agent (β-NA) due to the possible hydrogen-bonding interaction between β-NA and EA-UFPR.•The membrane with uniformly distributed pores and high porosity can be achieved from the samples with β-TC networks.Lots of works have been done on the pore formation of β nucleated PP membranes during stretching, and most of these works focus on the effects of crystal form and processing conditions on the performance of PP membrane. In our work, the crystalline morphology of β crystal was modulated by adding a small amount of ultrafine full-vulcanized powder rubber (EA-UFPR), and subsequently, the influence of crystalline morphology on pore-size distribution and porosity was investigated. It was interesting to find that the crystalline morphology changes from spherulites into large quantity of β-transcrystals (β-TCs) by adding EA-UFPR. The related transformation mechanism was investigated by polarized optical microscope (POM), differential scanning calorimetry (DSC) and rheological tests. It was found that the fibrils of β nucleating agent could be directly absorbed on the surface of EA-UFPR particles due to the possible hydrogen-bond interaction between them as evidenced by FTIR, which hindering the self-assembly of these fibrils into big framework. As a result, the tiny fibrils with fine dispersion induce the formation of β-TC networks instead of isolated spherulites. Furthermore, the membrane with uniformly distributed pores and high porosity can be achieved from the samples with β-TC networks. This is possibly related to their loosely-packed lamella and de-bonding of EA-UFPR particles during microvoids formation. This work provides a convenient and reliable strategy for the preparation of PP microporous membranes with high performance.
Co-reporter:Yi Zhou, Hua Deng, Feilong Yu, Hongwei Bai, Qin Zhang, Feng Chen, Ke Wang, Qiang Fu
Polymer 2016 Volume 99() pp:49-58
Publication Date(Web):2 September 2016
DOI:10.1016/j.polymer.2016.06.013
•The processing condition induced changes in flow field, temperature field, viscosity and shear time.•The changes as above largely influence the confinement of melt during processing, thus, their final phase morphology.•The moderate injection condition and thin mold favors the formation of alternating multi-layer structure.•The confinement of flow plays a key role on formation of alternating multi-layer structure.Polymeric materials with alternating multi-layer structure have gained much attention in the field of biomimic, where many methods were used to prepare materials with such structure for various functionalities. A simple method based on high speed thin-wall injection molding (HSTWIM) has been proposed in our previous studies for the easy fabrication of multi-layer functional polymeric materials. Herein, the effect of various injection processing parameters: injection distance, injection speed, mold temperature and mold thickness on the phase morphology and molecular orientation is studied. The processing condition induced changes in flow field, temperature field, viscosity and shear time are thought to largely influence the confinement of melt during processing, thus, their final phase morphology. It is observed that moderate injection distance, moderate injection speed, moderate mold temperature and thin mold favors the formation of such alternating multi-layer structure. Such study could provide guidelines for the fabrication of functional multi-layered structure through HSTWIM as well as control of phase morphology through confined flow.
Co-reporter:Hao Xiu, Yan Zhou, Chunmei Huang, Hongwei Bai, Qin Zhang, Qiang Fu
Polymer 2016 Volume 82() pp:11-21
Publication Date(Web):15 January 2016
DOI:10.1016/j.polymer.2015.10.034
•Three kinds of CB with different self-networking capabilities were used to tailor the phase morphology of PLA/PU blends.•CB with high self-networking capability could lead to an easier formation of more stable co-continuous-like structure.•The kinetics of CB self-networking in PLA/PU blends was studied by rheology.•The rheology-self-networking of fillers-phase morphology triadic correlation in fillers-filled polymer blends was established.Polymer blending has been intensively investigated in recent decades because it is a simple way to achieve high-performance polymeric materials. It has been demonstrated that the properties of polymer blends are largely determined by its phase morphology. Recently, a change of sea-island morphology to a unique co-continuous-like structure was observed by adding a small amount of filler particles with self-networking capability in polymer blends. The formation of co-continuous-like structure can impart polymer blends with a good stiffness-toughness balance. However, the underlying mechanism for the formation and evolution of this structure is still not clear. In this work, three types of carbon black (CB) with different self-networking capabilities was used to tailor the phase morphology of polylactide (PLA)/poly(ether)urethane (PU) blend with fixed ratio (85/15 wt/wt). It was found that adding CB with high self-networking capability could lead to an easier formation of co-continuous-like structure compared with those with low self-networking capability, as confirmed by SEM observations. The CB induced co-continuous-like structure was further investigated by rheology time sweep tests. It was found that the formation process and stability of co-continuous-like structure is not only dependent on CB content and CB self-networking capability, but also on sweep temperature and frequency. This work gives a deep insight into the key role of the self-networking capability of fillers in controlling the phase morphology of immiscible polymer blends which can provide guidance for preparing high-performance polymeric materials.
Co-reporter:Sha Deng;Xiao-dong Qi;Yan-ling Zhu;Hong-ju Zhou
Chinese Journal of Polymer Science 2016 Volume 34( Issue 10) pp:1270-1280
Publication Date(Web):2016 October
DOI:10.1007/s10118-016-1836-y
In the field of polymer/graphene nanocomposites, massive production and commercial availability of graphene are essential. Exfoliation of graphite to obtain graphene is one of the most promising ways to large-scale production at extremely low cost. In this work we illustrate a facile strategy for mass production of few-layered (≤ 10) graphene (FLG) via the newly explored ball milling. The achieved FLG concentration was determined by UV/Vis spectroscopy. The formation of FLG was proved by measuring the flake thickness by atomic force microscopy (AFM). Further Raman spectral studies indicated that the crystal structure of exfoliated flakes was preserved satisfactorily during this shear-force dominating process. To increase the maximum concentration obtainable, it’s critical to make a good parameter assessment. N-methylpyrrolidone (NMP) was used as a dispersing medium and the effect of milling parameters was systematically and quantitatively investigated, thus providing a criterion to optimize the milling process. We established the optimal values for solvent volume and initial weight of graphite. As for milling time, the production of FLG was enhanced with continuous milling according to the power law, but not linearly with increasing milling time. Moreover, the possible mechanism involved in milling process was also explored. Our work provides a simple method for graphite exfoliation and has great potential for improving thermal and electrical conductivity of polymer composites in the fields of engineering.
Co-reporter:Xiaodong Qi, Yilan Guo, Yuan Wei, Peng Dong, and Qiang Fu
The Journal of Physical Chemistry B 2016 Volume 120(Issue 42) pp:11064-11073
Publication Date(Web):October 4, 2016
DOI:10.1021/acs.jpcb.6b08536
The importance of filler–matrix interactions is generally recognized for mechanical property enhancement; their direct impact by physical confinement on diverse functional properties has remained poorly explored. We report here our effort in achieving versatile shape memory performances for a biodegradable poly(propylene carbonate) (PPC) matrix containing high contents of graphene oxide (GO). The excellent dispersion in the entire filler range (up to 20 wt %) allows precise morphological tuning, along with physical filler–matrix interactions, contributing overall to a strong nanoconfinement effect that positively affects the thermomechanical properties of nanocomposites. Only one glass-transition temperature (Tg) of PPC is detected when the GO content is below 10 wt %, corresponding to a slightly confined system, whereas two distinct Tg’s are observed with a GO content over 10 wt %, corresponding to a highly confined system. As such, a tunable multishape memory effect can be achieved simply by tuning the filler contents. A dual-shape memory effect (DSME) is observed for a slightly confined system, whereas a triple-shape memory effect (TSME) can be achieved by deformation at two distinct Tg’s for a highly confined system. More importantly, it is interesting to find that the switch temperature (Tsw) evolves linearly with the programing temperature (Tprog) for both slightly and highly confined systems, with Tsw ≈ Tprog for a highly confined system but Tsw < Tprog for a slightly confined system. Our work suggests a highly flexible approach to take advantage of the strong nanoconfinement effect by tuning the content of GO within a single polymer to access versatile SMEs, such as DSME and TSME, and the temperature memory effect.
Co-reporter:Huili Liu, Dongyu Bai, Hongwei Bai, Qin Zhang and Qiang Fu
Journal of Materials Chemistry A 2015 vol. 3(Issue 26) pp:13835-13847
Publication Date(Web):25 May 2015
DOI:10.1039/C5TA02017D
In recent years, there has been growing interest in developing poly(L-lactide)/carbon nanotube (PLLA/CNT) nanocomposites due to their considerable application value and potential. Unfortunately, the fabrication of high-performance PLLA/CNT nanocomposites still faces several obstacles mainly related to the low crystallization rate of the PLLA matrix as well as poor interfacial adhesion between the matrix and CNTs. In this work, we demonstrate a facile and promising route to simultaneously address these limitations by compositing PLLA with poly(D-lactide) grafted multi-walled carbon nanotubes (MWCNTs-g-PDLA) which can be synthesized via in situ ring-opening polymerization of D-lactide on the MWCNT surface. During melt-mixing of PLLA with the as-prepared MWCNTs-g-PDLA, the grafted PDLA chains and PLLA matrix chains tend to arrange side by side at the composite interface and finally co-crystallize into stereocomplex (SC) crystallites capable of serving as not only a highly active nucleating agent to dramatically accelerate matrix crystallization but also an effective interfacial enhancer to greatly improve the interfacial stress transfer efficiency. As a result, PLLA/MWCNTs-g-PDLA nanocomposites exhibit a much higher matrix crystallization rate and mechanical strength as compared to PLLA/MWCNTs-g-PLLA counterparts, where only limited physical entanglement between grafted and matrix chains forms across the interface. Moreover, both the crystallization rate and mechanical strength can be readily manipulated by tailoring the length of the grafted PDLA chains. This work could provide access to design advanced PLLA-based nanocomposites with fast matrix crystallization ability and outstanding mechanical properties via constructing multifunctional SC crystal structures at the interface.
Co-reporter:Wenjing Ji, Junyi Ji, Xinghong Cui, Jianjun Chen, Daijun Liu, Hua Deng and Qiang Fu
Chemical Communications 2015 vol. 51(Issue 36) pp:7669-7672
Publication Date(Web):24 Mar 2015
DOI:10.1039/C5CC00965K
Polypyrrole (PPy) encapsulated 3D flower-like NiO was prepared to investigate the role of PPy coating for high-performance electrodes. NiO@PPy showed a better electrochemical performance than pure NiO, and a “trade-off effect” between electrical conductivity and ion diffusion resistance was observed with different PPy coating thickness.
Co-reporter:Feilong Yu, Hua Deng, Hongwei Bai, Qin Zhang, Ke Wang, Feng Chen, and Qiang Fu
ACS Applied Materials & Interfaces 2015 Volume 7(Issue 19) pp:10178
Publication Date(Web):April 27, 2015
DOI:10.1021/acsami.5b00347
Various methods have been devoted to trigger the formation of multilayered structure for wide range of applications. These methods are often complicated with low production efficiency or require complex equipment. Herein, we demonstrate a simple and efficient method for the fabrication of polymeric sheets containing multilayered structure with enhanced barrier property through high speed thin-wall injection molding (HSIM). To achieve this, montmorillonite (MMT) is added into PE first, then blended with PP to fabricate PE-MMT/PP ternary composites. It is demonstrated that alternating multilayer structure could be obtained in the ternary composites because of low interfacial tension and good viscosity match between different polymer components. MMT is selectively dispersed in PE phase with partial exfoliated/partial intercalated microstructure. 2D-WAXD analysis indicates that the clay tactoids in PE-MMT/PP exhibits an uniplanar-axial orientation with their surface parallel to the molded part surface, while the tactoids in binary PE-MMT composites with the same overall MMT contents illustrate less orientation. The enhanced orientation of nanoclay in PE-MMT/PP could be attributed to the confinement of alternating multilayer structure, which prohibits the tumbling and rotation of nanoplatelets. Therefore, the oxygen barrier property of PE-MMT/PP is superior to that of PE-MMT because of increased gas permeation pathway. Comparing with the results obtained for PE based composites in literature, outstanding barrier property performance (45.7% and 58.2% improvement with 1.5 and 2.5 wt % MMT content, respectively) is achieved in current study. Two issues are considered responsible for such improvement: enhanced MMT orientation caused by the confinement in layered structure, and higher local density of MMT in layered structure induced denser assembly. Finally, enhancement in barrier property by confining impermeable filler into alternating multilayer structure through such simple and efficient method could provide a novel route toward high-performance packaging materials and other functional materials require layered structure.Keywords: barrier; clay; high speed thin wall injection molding; multilayered structure; orientation;
Co-reporter:Yuhan Li, Jiajia Yuan, Jian Xue, Fanyi Cai, Feng Chen, Qiang Fu
Composites Science and Technology 2015 Volume 118() pp:198-206
Publication Date(Web):30 October 2015
DOI:10.1016/j.compscitech.2015.09.004
Barium titanate (BT) particles coated with different thickness of polydopamine (PDA) layers were incorporated into polyvinylidene fluoride (PVDF) to investigate influence of PDA coating layers on dielectric properties of composites. It is found that PDA coating layers not only effectively improved the interfacial interaction between BT particles and matrix but also significantly affected dielectric properties. PVDF composites loaded with modified BT exhibits superior dielectric properties in comparison with unmodified BT. Interfacial polarization is substantially suppressed because the catechol groups of PDA are able to constrain the mobility of nomadic charge carriers and ionizable hydroxyl groups on surface of BT particles. As a result, dependency of dielectric constant on frequency attenuates and tan δ is lowered to below 0.050 (1 kHz). The effect of suppression on tan δ tends to be more prominent as the thickness of PDA coating layer increases. The tan δ derived from ionic relaxation polarization is also constrained due to the chelation of PDA catechol groups with migrated cations. The as-prepared composites possess high dielectric constant and ultralow tan δ, making them promising for the industrial application as embedded capacitors.
Co-reporter:Yongsheng Zhao, Bin Su, Feng Chen and Qiang Fu
Soft Matter 2015 vol. 11(Issue 11) pp:2300-2307
Publication Date(Web):16 Jan 2015
DOI:10.1039/C4SM02463J
This work reports the evolution of ordered nano-cylindrical structures in a thermoplastic elastomer, poly(styrene-b-isoprene-b-styrene) (SIS), utilizing a newly designed processing technique, so-called “dynamic-packing injection moulding”. In this injection moulding technique, controlled oscillating shears with different shear cessation times under constant pressure were applied on the moulded samples during cooling. It was found that these additional controlled oscillating shears resulted in a change of orientation in skin-core structures in these samples, compared with corresponding “reference” samples processed via traditional injection moulding (without controlled oscillating shears). For the “reference” samples, a highly oriented PS cylindrical structure combined with relatively weak lateral ordering was observed in their skin layers, whereas the lateral ordering of the PS nano-cylinders gradually disappeared when entering the core region. On the other hand, for the SIS samples obtained via “dynamic-packing injection moulding”, the orientation of the PS nano-cylinders in the skin layers was similar to the case of the “reference” sample due to their extremely fast cooling rate. However, the lateral ordering of these cylinders had been extended to the core region. With an increase in the cessation time, the lateral ordering of the PS nano-cylinders was further improved and finally resulted in hexagonal lateral packing along the flow direction in the mould. Furthermore, a mixture of parallel/perpendicular orientation of the cylinders relative to the flow direction was found, particularly when the cessation time was short (such as 3 s). We speculated that this specific perpendicular orientation was a transient state for development of a final parallel orientation aligned with the flow direction with increasing cessation time, accompanied by a further enhancement of the nano-cylindrical parallel orientation. This study could provide a better understanding of the shear and relaxation effects on the structural evolution of this class of thermoplastic elastomers, enhancing supramolecular ordered cylindrical orientation in the core region, and paving a way to tune the nano-structures of block copolymers via this new processing technique to achieve desired properties.
Co-reporter:Siyao Liu, Hua Deng, Yun Zhao, Shijie Ren and Qiang Fu
RSC Advances 2015 vol. 5(Issue 3) pp:1910-1917
Publication Date(Web):27 Nov 2014
DOI:10.1039/C4RA09147G
Poly(3,4-ethylenedioxylthiophene):poly(styrene sulfonate) (PEDOT:PSS) has been investigated as a thermoelectric (TE) material extensively. Post-treatment using various solvents has been used to improve its TE performance. Nevertheless, the effects of using mixed co-solvents and post-treatment temperature have hardly been systematically studied. Herein, the TE properties of PEDOT:PSS thin films after solvent post-treatment are investigated. Different ratios of ethylene glycol (EG) and dimethyl sulfoxide (DMSO) as co-solvents and different treatment temperatures are used to optimize the TE properties. It is demonstrated that DMSO post-treatment is more efficient than the co-solvent or EG single solvent at removing insulating PSS from these thin films due to its high dielectric constant. DMSO treated specimens exhibit a power factor as high as 28.95 μW mK−2. Under room temperature post-treatment, PSS is depleted and conformational changes of PEDOT are triggered. This leads to higher electrical conductivity, without an apparent effect on the redox level of PEDOT. Under higher treatment temperature, PEDOT:PSS shows a certain degree of reduced form which leads to a higher Seebeck coefficient. Meanwhile, the electrical conductivity drops and the Seebeck coefficient increases first and then drops with increasing temperature. The reason that the Seebeck coefficient increases is mainly because of the redox level variation under high temperature. With the combination of co-solvent and temperature, the highest power factor of 37.05 μW mK−2 is obtained for PEDOT:PSS post-treated with DMSO at 120 °C. Assuming a thermal conductivity of 0.17 W m K−1, the corresponding ZT of such PEDOT:PSS film is 0.065. This demonstrates that post-treatment is an effective way to optimize the TE properties of PEDOT:PSS. Furthermore, the combined use of solvent and temperature shows the potential of effective tuning of the TE properties of PEDOT:PSS via a more simple and environmentally friendly process.
Co-reporter:Yan Zhou, Hao Xiu, Jia Dai, Hongwei Bai, Qin Zhang and Qiang Fu
RSC Advances 2015 vol. 5(Issue 39) pp:30912-30919
Publication Date(Web):24 Mar 2015
DOI:10.1039/C5RA05115K
In this study, we simultaneously introduced both poly(lactic acid) (PLA) and multiwalled carbon nanotubes (CNTs) into the polyurethane (PU) matrix via melt blending, to achieve balanced mechanical properties and good conductivity. Different contents of PLA (0–30 wt%) and CNTs (0–3.0 wt%) were used in this work. A significant improvement in tensile strength at 300% strain and Young's modulus were observed, which could not be obtained by incorporating either PLA or CNTs with PU separately. Particularly, the ternary composites containing a large amount of PLA (30 wt%), 70PU/30PLA/CNTs composites, exhibit superior mechanical properties compared to other composites with less PLA content but the same amounts of CNTs. Moreover, the ternary composites showed better electrical conductivity compared with the binary counterpart. SEM observations demonstrated that PLA particles and CNTs are separately dispersed in the PU matrix. It was found that PLA particles remain spherical and their size increases with increasing PLA content up to 30 wt%, while a network structure of CNTs is formed with increasing its content, which was also confirmed via dynamic rheological analysis. Interestingly, some CNTs were seen to be located in the interfaces between PLA particles and the PU matrix for 70PU/30PLA/CNTs composites, namely, some CNTs exhibit a nano-bridge effect between PU and PLA. We hypothesized that the nano-bridge structure of CNTs in the composites could mainly contribute to the observed enhancement of mechanical properties and electrical conductivity.
Co-reporter:Yanling Zhu, Yongsheng Zhao, Sha Deng, Qin Zhang and Qiang Fu
RSC Advances 2015 vol. 5(Issue 77) pp:62797-62804
Publication Date(Web):09 Jul 2015
DOI:10.1039/C5RA05778G
In this work, ultrafine full-vulcanized powdered rubber (EA-UFPR) was incorporated into β-nucleated isotactic polypropylene (β-iPP) in order to investigate the combined effects of EA-UFPR and β-nucleation on mechanical properties and heat distortion temperature (HDT) of β-iPP. A large enhancement of toughness verified as a synergistic effect had been achieved by adding a small amount of EA-UFPR (≤2 wt%) into β-nucleated iPP. Decreased crystallization kinetics and even more interestingly, a transformation of crystalline morphology from β-spherulites to bundle-like β-crystals were observed due to a possible retarded self-assembly of the nucleating agent by adding small amounts of EA-UFPR. On one hand, the combined effects between EA-UFPR particles and β-crystalline morphology on promoting the plastic deformation of the matrix play important roles in enhancing the toughness. On the other hand, a unique interconnected structure composed by the bundle-like crystals and dispersed EA-UFPR particles was proposed for the improvement in impact strength and HDT. Our work provides a new way to control crystalline morphology and largely improve the toughness and heat distortion temperature of iPP, which are particularly important for the industrial application of iPP.
Co-reporter:Xin Hu, Chengzhen Geng, Guanghui Yang, Qiang Fu and Hongwei Bai
RSC Advances 2015 vol. 5(Issue 67) pp:54488-54496
Publication Date(Web):15 Jun 2015
DOI:10.1039/C5RA09685E
It is believed that the good toughness of β-modified polypropylene (PP) is due to its easier lamellar slippage compared with that of α-modified PP, while the improvement in toughness of PP caused by annealing is due to increased chain mobility in the amorphous part of PP. The aim of this work is to reveal the combined effects of the matrix crystalline structure and amorphous chain mobility on the low temperature toughness of PP/ethylene–octene copolymer (POE) blends by β-modification and annealing. An impact test was performed over a wide range of temperatures (room temperature, 0 °C, −20 °C and −40 °C) to verify the enhancement in toughness, and various characterizations were carried out to inspect the structural evolution and toughening mechanism. The results show that β-modification and annealing will work synergistically to toughen the blend and reduce the POE content necessary for effective toughening over the temperature range tested, due to the synergetic enhancement in the matrix cavitation ability. Besides, the tensile properties will not be lowered by β-modification and annealing. This work not only provides a more efficient way to improve the impact resistance of polymers with stiffness–toughness balance, but also demonstrates the vital role of matrix microstructures on the toughness of the material.
Co-reporter:Tian-Xiang Jin, Xian-Yin Zhang, Yun-Feng Tao, Dan Wang, Feng Chen and Qiang Fu
RSC Advances 2015 vol. 5(Issue 75) pp:61364-61370
Publication Date(Web):09 Jul 2015
DOI:10.1039/C5RA11390C
Phosphorus-containing poly(butylene succinate-co-3-hydroxyphenylphosphinyl-propionate) (PBSH) was synthesized through esterification and melt copolycondensation of succinic acid (SA), 1,4 butanediol (BD) and 3-hydroxyphenylphosphinyl-propionic acid (HPPPA). The chemical structure of PBSH was confirmed using Fourier transform infrared spectroscopy (FTIR) and 1H NMR spectroscopy. It is found that the addition of HPPPA can improve the initial decomposition temperatures of copolyesters. The LOI values of the PBSHs were increased from 22.0% to 35.0% and the UL-94 ratings of vertical burning were improved to V-0 with a relatively low content of phosphorus containing comonomer. Furthermore, we used melt postpolycondensation to increase the molecular weights of the copolyester and found that a copolymer with enough high molecular weight can maintain its good mechanical properties for practical applications.
Co-reporter:Di Han, Qing–Yun Guo, Wen-Bin Zhang, Liu-Xu Liu and Qiang Fu
RSC Advances 2015 vol. 5(Issue 86) pp:70051-70058
Publication Date(Web):11 Aug 2015
DOI:10.1039/C5RA13424B
In this study, we first synthesised dumbbell-shaped Janus molecular nanoparticles (MNPs) based on polyhedral oligomeric silsesquioxane (POSS) and [60]fullerene (C60) (POSS–C60) via Bingel–Hirsch cyclopropanation, with the goal of combining their unique physical and chemical characteristics. The successful preparation of this new Janus POSS–C60 was confirmed by NMR, FT-IR and MALDI-TOF MS experiments. Then a co-precipitation method was used to prepare four kinds of polystyrene (PS) nanocomposites, namely, PS/POSS, PS/C60, PS/POSS/C60 (which is a physical mixture of PS, POSS and C60) and PS/POSS–C60. The effect of POSS, C60, POSS/C60 and POSS–C60 on the properties of PS was investigated. SEM results suggest a good and similar dispersion for all of the four prepared PS nanocomposites. The glass transition temperature (Tg) of PS is decreased with increasing filler content in a similar way for the four kinds of PS nanocomposites. Rheological result suggests a similar trend of the storage modulus change with increasing filler content, disregarding the chemical structure of fillers and combination of fillers. However, it was interesting to find that POSS alone is good for mechanical property reinforcement and C60 alone is good for thermal stability reinforcement for PS, while POSS–C60, which is a particle with chemically bonded POSS and C60, exhibit better reinforcement of both mechanical properties and thermal stability compared with pristine POSS, C60 and POSS/C60. Our work provides some new ideas for the preparation of polymer nanocomposites with novel particle shapes and unique properties.
Co-reporter:Zhen Li, Chengxiao Sun, Xiaoyu Li, Qin Zhang and Qiang Fu
RSC Advances 2015 vol. 5(Issue 104) pp:85442-85445
Publication Date(Web):02 Oct 2015
DOI:10.1039/C5RA15358A
Microfibrillar composites (MFCs) can be created when the viscosity ratio of polypropylene (PP) and olefinic block copolymer (OBC) is well controlled. PP can be easily deformed into well-refined microfibrils in OBC with different architectures. The mechanical properties of the obtained MFCs are prominently improved.
Co-reporter:Xin Xu, Xuelin Yao, Feng Chen and Qiang Fu
RSC Advances 2015 vol. 5(Issue 5) pp:3733-3742
Publication Date(Web):03 Dec 2014
DOI:10.1039/C4RA13674H
Solvent-induced mechanical instability in a cross-linked poly(styrene-block-dimethylsiloxane) (PS-PDMS) film attached to a rigid substrate was systematically investigated. Through swelling with appropriate solvent vapor, a unique network of folds could be constructed successfully without the wrinkle-to-fold transition. Instead, small holes resulting from the mesostructural organization of PS-PDMS formed as nuclei to induce formation and growth of invaginated folds resembling creases which then constructed a network of invaginated folds. A complete network of sharp folds could be obtained after the two edges of a valley were combined into a sharp fold. The morphology and kinetics were closely related to the solvent solubility parameter and saturated vapor pressure. We varied the ratio between a relatively good solvent vapor and a poor solvent vapor, and so produced a slower dynamic process to precisely control the surface morphology. Poorly ordered cylinders with varied sizes resulting from strong cross-linking and spatial restrictions imposed by the network of folds could be obtained.
Co-reporter:Yongsheng Zhao, Yanling Zhu, Guopeng Sui, Feng Chen, Qin Zhang and Qiang Fu
RSC Advances 2015 vol. 5(Issue 100) pp:82535-82543
Publication Date(Web):14 Sep 2015
DOI:10.1039/C5RA13864G
In this study, the orientation, structure and mechanical performance of a series of uniaxially oriented films based on olefin block copolymers (OBC) have been investigated in terms of the differences in hard block content and draw ratio (DR). Three OBCs with different hard block contents of 35 wt%, 25 wt% and 12 wt% were used. For un-stretched films, a change from close-packed spherulites into tiny crystallites is observed with decreasing hard block content, accompanied by an almost linear decrease in crystallinity. However, the change in mechanical properties does not follow the same path, with obviously higher tensile strength and modulus for OBC-35, but a lower and almost the same tensile strength and modulus for OBC-25 and OBC-12, in spite of the big difference in hard block content and crystallinity between them. For melt-stretched films, the degree of orientation of the amorphous phase is almost the same and slightly increases with the increase in the draw ratio for the three OBCs, disregarding their hard block contents. Crystalline orientation and shish content are much higher for OBC-35, and an obvious increase is seen as the draw ratio increases from 4.95 to 8, corresponding to the sharp increase in Young's modulus and stress. For OBC-25 and OBC-12, similar crystalline orientation and shish content are seen, which increase linearly with draw ratio and are consistent with the linear increase in modulus and stress as the draw ratio increases. Our study demonstrates the importance of the hard block content of OBC to determine the mechanical properties and the response to external stretching. A critical hard block content exists (in this case 35 wt%), above which a strong network is constructed by the hard block crystalline phase, resulting in a higher tensile strength and modulus. This strong network is destroyed as the draw ratio reaches a certain value (herein, 4.95 to 8), leading to an obvious increase in crystalline orientation, as well as a sharp increase in tensile strength and modulus. When the hard block is below the critical content (herein, 25 wt% and 12 wt%), the network constructed by the hard block is weak and less dependent on its content.
Co-reporter:Bowen Yu, Sirui Fu, Zhiqiang Wu, Hongwei Bai, Nanying Ning and Qiang Fu
RSC Advances 2015 vol. 5(Issue 124) pp:102219-102227
Publication Date(Web):16 Nov 2015
DOI:10.1039/C5RA18799K
Molecular dynamics simulations were utilized to study the interfacial crystallization between polyethylene (PE) and single walled carbon nanotubes (SWCNTs). The early stages of PE crystallizing on the surface of SWCNTs and a SWCNT bundle were studied for comparison. The result showed that the PE chain tended to stabilize in the grooves of the SWCNT bundle and extended along the direction of SWCNTs afterwards. The early arrived chain could then lead to a regular arrangement of other chains and this was conducive to the formation of interfacial crystallization. Also, the inner mechanism of interfacial crystallization in solution and melt had been investigated. It was found that in solution, the interfacial crystallization of PE is a spontaneous process. However, in melt the interfacial crystallization strongly depended on the pre-orientation of the PE chains. This will help to understand the origin of polymer interfacial crystallization and guide the fabrication of high performance polymer/CNT nanocomposites via interfacial crystallization.
Co-reporter:Li Zhang, Hua Deng, Siyao Liu, Qin Zhang, Feng Chen and Qiang Fu
RSC Advances 2015 vol. 5(Issue 128) pp:105592-105599
Publication Date(Web):02 Dec 2015
DOI:10.1039/C5RA22240K
Post-treatment of PEDOT:PSS films to fabricate high performance thermoelectric (TE) materials has been widely studied. The depletion of PSS and tuning the redox level of PEDOT have been considered important. The effective control of these two issues is crucial, yet has not been systematically investigated. Herein, HI and DMSO are used to post-treat PEDOT:PSS films, issues including using these solvents in a step-wise fashion, using solvent or vapour and treatment time are studied. HI is found to have both a physical doping and reducing effect on PEDOT:PSS simultaneously. However, HI solution or vapour could not remove most of the excess PSS to obtain high electrical conductivity. Therefore, DMSO is used to achieve this. Subsequently, HI vapour was used to alter the redox level. Through this method, the power factor reaches as high as 45.02 μW mK−2, which is over 5000 times higher than the as spun film. These films are characterized by different methods, including: AFM, XPS, UV, SEM and Raman spectroscopy. It is concluded that such enhancement in TE properties is caused by two issues: the depleting effect of PSS by DMSO and oxidation level change of PEDOT by HI vapour. The former leads to enhanced electrical conductivity and the latter leads to reduced charge carrier concentration, thus, enhanced Seebeck coefficient. It is thought that such a two-step solvent post-treatment method could offer a novel route to optimize the TE properties of PEDOT:PSS based materials.
Co-reporter:Meng Wu, Ke Wang, Qin Zhang and Qiang Fu
RSC Advances 2015 vol. 5(Issue 117) pp:96353-96359
Publication Date(Web):26 Oct 2015
DOI:10.1039/C5RA12271F
In recent years, biodegradable polymers derived from bioresources have received more and more attention. Making a new type of blend by compounding biodegradable polymer with a petroleum-based polymer is now an important method of preparation for such polymers. A key issue to dominate the quality of a polymer blend is manipulation of multiphase morphology. In this study, a bio-degradable polymer, poly(lactic acid) (PLA), was blended with a new thermoplastic elastomer, olefin block copolymer (OBC), through melt mixing using ethylene-glycidyl methacrylate (EGMA) as a compatibilizer. In this blending system, only physical interaction exists between OBC and EGMA, but chemical reaction occurs between PLA and EGMA. This significant asymmetry of interaction and compatibility offers the opportunity for yielding special dispersed-phase structures during melt blending. By altering the blending sequence, EGMA amount, blend time, and OBC hard-segment content, some interesting substructures of dispersed-phase were achieved such as core–shell, subinclusions, co-continuous, salami and micelle. This study offers good insight into designing the multiphase morphology via competition between compatibilization and intra-particle reaction.
Co-reporter:Dongsheng Tan;Liuxu Liu;Zhen Li
Journal of Biomedical Materials Research Part A 2015 Volume 103( Issue 8) pp:2711-2719
Publication Date(Web):
DOI:10.1002/jbm.a.35403
Abstract
To improve blood compatibility of polyurethane (PU), phospholipids grafted carbon nanotubes (CNTs) were prepared through zwitterion-mediated cycloaddition reaction and amide condensation, and then were added to the PU as fillers via solution mixing to form biomimetic surface. The properties of phospholipids grafted CNTs (CNT-PC) were investigated by thermal gravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and proton nuclear magnetic resonance (1H NMR). The results indicated that the phospholipids were grafted onto CNTs in high efficiency, and the hydrophilicity and dispersibility of the modified CNTs were improved effectively. The structures and properties of composites containing CNT-PC were investigated by optical microscope, XPS, and water contact angles. The results indicated that phospholipids were enriched on the surface with addition of 0.1 wt % of CNT-PC, which significantly reduced protein adsorption and platelet adhesion. The method of carrying phospholipids on the nanofiller to modify polymers has provided a promising way of constructing biomimetic phospholipid membrane on the surface to improve blood compatibility. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 103A: 2711–2719, 2015.
Co-reporter:Yao Gao;Yi Wu;Maoqing Liang
Journal of Applied Polymer Science 2015 Volume 132( Issue 25) pp:
Publication Date(Web):
DOI:10.1002/app.42119
ABSTRACT
For polymer composites, interfacial crystalline structures retain an important role in the macroscopic properties and are significantly affected by the processing conditions, such as the temperature, time, and external field. In this study, the transcrystallization behavior of the carbon nanotube fiber and isotactic polypropylene composite was investigated by polarizing light microscopy. The influence of the formation of the transcrystalline layer on the interfacial adhesion was evaluated by a single-fiber fragmentation test. The results show that the growth rate of the transcrystalline layer was strongly influenced by the isothermal crystallization temperature, and the interfacial shear strength was markedly enhanced by the formation of the layer. The interfacial adhesion was further increased with the gradual perfection and growth of transcrystallinity. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42119.
Co-reporter:Liang He, Changyu Tang, Xin Xu, Peng Jiang, Woon-Ming Lau, Feng Chen, Qiang Fu
Surface and Coatings Technology 2015 Volume 261() pp:311-317
Publication Date(Web):15 January 2015
DOI:10.1016/j.surfcoat.2014.11.013
•Nano-scale wrinkle patterns are fabricated in ultrathin polymer films.•The formation of wrinkle patterns is systematically investigated.•This approach shows good applicability in three representative polymer films.•Ordered surface patterns are generated by using nano-patterned silicon template.This paper presents an efficient and simple processing method for the fabrication and regulation of nano-scale wrinkle patterns. The stiff film is created through cross-linking the surface of ultrathin polymer film within twenty nanometers by using the hyperthermal hydrogen induced cross-linking (HHIC) method, and then the bilayer is heated above the glass transition temperature of the polymer before quenched to room temperature. In this way, wrinkle patterns with wavelength ranging from 150 to 300 nm are prepared. And a morphology transition between the pattern of single points (convex bumps) and the pattern of ridges (labyrinth) is observed. The formation of wrinkle patterns is systematically investigated as functions of the thickness of original ultrathin film, the time of HHIC treatment, the annealing temperature and the chemical structure of polymers. Furthermore, nano-patterned silicon wafer is used as a template to create multiscale, anisotropic wrinkle patterns.
Co-reporter:Yu-ling He;Yi-lan Guo;Rui He;Tian-xiang Jin
Chinese Journal of Polymer Science 2015 Volume 33( Issue 8) pp:1176-1185
Publication Date(Web):2015 August
DOI:10.1007/s10118-015-1667-2
Poly(bisphenol A carbonate) (BPA-PC) was post-polymerized by solid-state polymerization (SSP) after supercritical CO2-induced crystallization in low molecular weight particles prepolymerized via melt transesterification reaction. The effects of the crystallization conditions on melting behavior and SSP of BPA-PC were investigated with differential scanning calorimetry (DSC), Ubbelohde viscosity method and gel permeation chromatography (GPC). The reaction kinetics of the SSP of crystallized prepolymers was studied as a function of reaction temperatures for various reaction periods. As a result, the viscosity average molecular weight of BPA-PC particles (2 mm) increased from 1.9 × 104 g/mol to 2.8 × 104 g/mol after SSP. More importantly, the significantly enhanced thermal stability and mechanical properties of solid-state polymerized BPA-PC, compared with those of melt transesterification polymerized BPA-PC with the same molecular weight, can be ascribed to the substantial avoidance of undergoing high temperature during polymerization. Our work provides a useful method to obtain practical product of BPA-PC with high quality and high molecular weight.
Co-reporter:Bowen Yu, Sirui Fu, Zhiqiang Wu, Hongwei Bai, Nanying Ning, Qiang Fu
Composites Part A: Applied Science and Manufacturing 2015 Volume 73() pp:155-165
Publication Date(Web):June 2015
DOI:10.1016/j.compositesa.2015.02.027
In this work, molecular dynamics simulations were utilized to probe the interfacial enhancement between aromatic polymers and single walled carbon nanotube (SWCNT) induced by molecular orientation. Two aromatic polymers, polyphenylene sulfide (PPS) and polystyrene (PS) were chosen for comparison study. It was found that orientation of polymer chain could bring about an obvious promotion in interfacial interaction for both systems. In PPS/SWCNT systems, the increased interfacial interaction energy was due to the easy formation of offset π–π stacking, while in PS/SWCNT systems the formation of edge-to-face π–π stacking contributed to the enhancement. Polymer/SWCNT composites were also constructed and a similar interfacial enhancement was observed as well. The mechanism of the orientation induced enhancement was a combination of forming more π–π stacking and better coating effect. This will help to deepen the understanding of interfacial interaction in aromatic polymers/carbon nanotubes composites and guide the fabrication of high performance materials.
Co-reporter:Yuhan Li, Mao Fan, Kai Wu, Feilong Yu, Songgang Chai, Feng Chen, Qiang Fu
Composites Part A: Applied Science and Manufacturing 2015 Volume 73() pp:85-92
Publication Date(Web):June 2015
DOI:10.1016/j.compositesa.2015.02.015
Graphene with polydopamine (PDA) coating layer which displays promoted dispersibility in organic solvent was prepared through self-polymerization of dopamine onto graphene oxide (GO) and subsequent chemical reduction. The PDA coated reduced GO (RDGO) is homogeneously incorporated into poly(vinylidene fluoride) (PVDF) matrix, which exhibit a percolation threshold at 0.643 wt%. The dielectric constant of PVDF with 0.70 wt% RDGO increases to 176, about 17 times of neat PVDF. Importantly, the loss tangent is suppressed to 0.337 due to reduction of the concentration and mobility of ionizable carboxylic groups by PDA. The enhancement of dielectric constant probably rises from duplex interfacial polarization induced by graphene–semiconductor interface, and semiconductor–insulator interface. The composites displays advantages in excellent dielectric properties and good flexibility and processability guaranteed by low loading of RDGO, which is suitable for the development of dielectric materials for energy storage.
Co-reporter:Tian-Xiang Jin, Chuan Liu, Mi Zhou, Song-gang Chai, Feng Chen, Qiang Fu
Composites Part A: Applied Science and Manufacturing 2015 Volume 68() pp:193-201
Publication Date(Web):January 2015
DOI:10.1016/j.compositesa.2014.09.025
Poly(butylene succinate) (PBS)/graphene oxide (GO) nanocomposites were fabricated via in situ polymerization with very low GO content (from 0.03 to 0.5 wt%). The microstructures of the nanocomposites were characterized with Raman spectroscopy, fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), sedimentation experiments and atomic force microscopy (AFM). The results showed that PBS chains have been successfully grafted onto GO sheets during in-situ polymerization, accompanied by the thermo-reduction from GO to graphene. The grafted GO displayed a great nucleating effect on PBS crystallization, resulting in largely improved crystallization temperature and decreased spherules size. A simultaneous enhancement in tensile strength and elongation was achieved for PBS/GO nanocomposites fiber. Meanwhile, increase in hydrolytic degradation rate was also observed for these nanohybrids. Our result indicates that using very low content GO is a simple way to achieve good dispersion yet with remarkable property enhancement for polymer/GO nanocomposites.
Co-reporter:Cheng-zhen Geng;Xin Hu;Guang-hui Yang;Qin Zhang
Chinese Journal of Polymer Science 2015 Volume 33( Issue 1) pp:61-69
Publication Date(Web):2015 January
DOI:10.1007/s10118-015-1558-6
Chitosan/cellulose nanocrystals (CS/CNCs) composites were prepared with different contents of CNCs. Due to the homogeneous dispersion of CNCs and the strong interfacial interactions resulting from hydrogen bonding between CS chains and CNCs, the transparency of CS is well retained and the overall mechanical properties of CS are significantly improved. Furthermore, because both CS and CNCs are biocompatible materials, cell proliferation test shows that the obtained composites are noncytotoxic and can potentially meet safety requirements of biomedical applications. These advantages pave the way of potential applications of CS in the field of commercial plastics and encourage the use of CS as environment-friendly material and biomedical material.
Co-reporter:Bin Su;Yong-sheng Zhao;Feng Chen 陈枫 傅强
Chinese Journal of Polymer Science 2015 Volume 33( Issue 7) pp:964-975
Publication Date(Web):2015 July
DOI:10.1007/s10118-015-1649-4
The relationship between microphase structure and mechanical response of the binary blends consisting of polystyrene-block-polyisoprene-block-polystyrene copolymer and low molecular weight polystyrene has been investigated. Low molecular weight polystyrene was chosen to obtain uniformly solubilized nano-blends without macrophase separation. The specimens were solution-cast by adding different amounts of homo-polystyrene to acquire different microphase structures. Small angle X-ray scattering (SAXS), transmission electron microscopy (TEM) and atom force microscopy (AFM) have been used to study the microdomain and grain structure. It is observed that the structural changes in d-spacing and grain size on account of different amounts of polystyrene alter the mechanical behavior in both monotonic tensile and cyclic tests. The elastic and the Mullins effects are strongly sensitive to the changes in d-spacing and grain sizes. Moreover, the sample with bi-continuous structure shows the largest tensile strength and Mullins effect. In addition, the Mooneye-Rivlin phenomenological model was used to evaluate and explore the relationship between the polymer topological networks and the rubber elasticity of these styrenic nano-blends.
Co-reporter:Yongsheng Zhao, Zhenwei Liu, Bin Su, Feng Chen, Qiang Fu, Nanying Ning, Ming Tian
Polymer 2015 Volume 63() pp:170-178
Publication Date(Web):20 April 2015
DOI:10.1016/j.polymer.2015.03.011
•Shear destructed EPDM aggregates into nano-particles.•Shear induced high crystal orientation of PP phase.•A simultaneous enhancement was achieved.In this study, in order to investigate the influence of melt shearing on the phase morphology and mechanical performance of PP/EPDM thermoplastic vulcanizates (TPVs), the oscillatory melt shear was successively applied on the TPV melt in the mold cavity during the packing stage of injection molding by a modified facility, called dynamic-packing injection molding. For a clear comparison, conventional injection molding was also used. It is shown that conventional injection-molding results in large EPDM rubber aggregates with dimensions of ∼1.5 μm dispersed in the PP matrix. To our surprise, well-dispersed nanoscale EPDM particles with dimensions of ∼40 nm have been achieved for the first time when introducing oscillatory melt shearing, in additional to a largely enhanced molecular orientation for PP matrix. As a result, a simultaneous improvement of tensile strength and elongation has been achieved for dynamic packing injection molded samples. In addition, step cycle tests showed typical “Mullins effect” for both conventional injection-molded samples and dynamic packing injection molded samples but improved fatigue resistance for dynamic packing injection molded ones. To isolate the contribution of PP matrix orientation and nanoscale EPDM particle on the tensile behavior of PP/EPDM TPVs, thermal annealing of injection molded samples were carried out to eliminate the orientation of PP matrix. It was found that the tensile strength is decreased but the elongation at break is maintained after annealing of dynamic packing injection molded samples. By comparing the property change before and after annealing, it is concluded that the orientation of PP matrix is in great favor of Young's modulus and tensile strength while the enhanced elongation at break is directly corresponding to the decreased rubber size and improved dispersion in TPVs. Our work demonstrates the strong effect of melt shearing on the breakup of rubber particles and matrix orientation of TPVs as well. The isolation of the contribution of PP matrix orientation and rubber particle size on the tensile behavior of TPVs provides guidance for the preparation of new TPVs with high performance.
Co-reporter:Xin Xu, Zhoukun He, Qi Wang, Feng Chen, and Qiang Fu
Langmuir 2015 Volume 31(Issue 16) pp:4605-4611
Publication Date(Web):April 6, 2015
DOI:10.1021/acs.langmuir.5b00340
In this article, we systematically studied the self-assembly of poly(styrene-block-dimethylsiloxane) (PS-b-PDMS) on a poly(dimethylsiloxane) (PDMS) substrate with nanoscale channels. The channeled PDMS substrate was achieved by a simple replica molding method. To decrease the effect that the subsequent solvent treatments had in distorting the soft PDMS substrate, a simple UV/O3 treatment was provided before the self-assembly, resulting in a relatively stable, harder and hydrophilic silicon oxide (SiO2) layer on the channeled PDMS surface. Ultimately, the isotropic SiO2 nanopatterns with spherical and long cylindrical morphologies were successfully fabricated by the self-assembly of two kinds of PS-b-PDMS on the PDMS substrate with nanoscale channels, respectively. In particular, we demonstrated that the introduction of isotropic SiO2 patterns is an effective approach to greatly enhance anisotropic wetting rather than that of the anisotropic structure with channels.
Co-reporter:Hua Deng, Lin Lin, Mizhi Ji, Shuangmei Zhang, Mingbo Yang, Qiang Fu
Progress in Polymer Science 2014 Volume 39(Issue 4) pp:627-655
Publication Date(Web):April 2014
DOI:10.1016/j.progpolymsci.2013.07.007
Since the emergence of large aspect ratio and multifunctional conductive fillers, such as carbon nanotubes, graphene nanoplates, etc., conductive polymer composites (CPCs) have attracted increasing attention. Although the morphological control of conductive networks in CPCs has been extensively investigated as an important issue for the preparation of high performance CPCs, recent extensive progress has not been systematically addressed in any review. It has been observed that the morphological control of conductive networks during the preparation of CPCs has crucial influence on the electrical properties of these composites. Several methods have been shown to be able to control the network structure, and thus, tune the electrical properties of CPCs, including the use of shear, polymer blends, thermal annealing, mixed filler, latex particle etc. Moreover, many novel and exciting applications have been extensively investigated for CPCs, such as stretchable conductor, electroactive sensors, shape memory materials and thermoelectric materials, etc. Therefore, the morphological control of conductive network in CPCs is reviewed here. Issues regarding morphology characterization methods, morphological control methods, resulted network morphology and electrical properties are discussed. Furthermore, the use of CPCs as electroactive multifunctional materials is also reviewed.
Co-reporter:Ke Wang, Feng Chen, Zhongming Li, Qiang Fu
Progress in Polymer Science 2014 Volume 39(Issue 5) pp:891-920
Publication Date(Web):May 2014
DOI:10.1016/j.progpolymsci.2013.05.012
Every day, numerous polymer materials are fabricated into specific articles with definite sizes, shapes and forms using polymer processing. Obviously, polymer processing has become one of the most active areas of polymer science and engineering. The key is to profoundly explore the processing-structure-performance relations for various polymer-based materials. From a structure-dominated performance point of view, the ultimate physical/chemical properties of polymer articles are directly related to their internal multiscale (hierarchical) structures, which range from the molecular, nanometer, submicron and micron scale to the mesoscopic level. Because the features of hierarchical structures strongly depend on the external fields that are imposed during processing, many structural items, such as the chain configuration, crystalline polymorphism, orientation and phase separation behavior, can be well or precisely controlled, resulting in significant variations in the hierarchical structure. Due to developments in mechanical techniques, various external fields, such as thermal, shear, extension, ultrasonic, electronic, magnetic and super-critical fluid fields, may be introduced into polymer processing, leading to significant improvements in the tailoring of the microstructure/morphology via processing. This process is characterized by an “externally applied field determined hierarchical structure”, i.e., a “structuring” processing, which represents an advanced trend in modern polymer processing and is the topic of this review. This contribution includes the following: (1) an introduction, (2) the in situ monitoring of polymer processing, (3) progress in “structuring” processing and (4) concluding remarks and perspectives.
Co-reporter:Dongsheng Tan, Zhen Li, Xuelin Yao, Chunlan Xiang, Hong Tan and Qiang Fu
Journal of Materials Chemistry A 2014 vol. 2(Issue 10) pp:1344-1353
Publication Date(Web):03 Dec 2013
DOI:10.1039/C3TB21473G
To study the influence of fluorinated surfaces and biomimetic surfaces on the improvement of the blood compatibility of polymers, three monomers containing a fluorinated tail and/or phosphorylcholine groups were designed and synthesized, and were then introduced into polyurethanes based on 4,4′-diphenylmethane diisocyanate (MDI), poly(tetramethylene glycol) (PTMG) and 1,4-butanediol (BDO) via end-capping. The bulk and surface characterization of the polyurethanes was carried out by dynamic mechanical analysis (DMA), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopic analysis (XPS), atomic force microscope (AFM), and water contact angle measurements. The results indicate that the fluorocarbon chains can drive the phosphorylcholine groups to aggregate at the surface of polyurethane, and the two components show spontaneous arrangement to adapt to the environment when in contact with water. The preliminary evaluation of hemocompatibility was carried out via fibrinogen adsorption and platelet adhesion. The fluorocarbon chains and phosphorylcholine groups showed a synergistic effect on the improvement of hemocompatibility.
Co-reporter:Xiaodong Qi, Xuelin Yao, Sha Deng, Tiannan Zhou and Qiang Fu
Journal of Materials Chemistry A 2014 vol. 2(Issue 7) pp:2240-2249
Publication Date(Web):29 Nov 2013
DOI:10.1039/C3TA14340F
A novel water-induced shape memory polymer based on polyvinyl alcohol (PVA) was prepared by introducing graphene oxide (GO). Due to the strong hydrogen bonding interaction between PVA and GO, some additional physically cross-linked points could be formed in PVA, which largely improved shape memory properties of PVA. Solvent-induced shape memory behavior was observed by immersing PVA/GO nanocomposites in water. The water-induced shape recovery was due to the decrease of glass transition temperature and storage modulus. This could be explained by the swelling plasticizing effect of water on PVA, as indicated by the obvious expansion in volume of PVA. On the other hand, the weakened hydrogen bonding between PVA and GO was also observed after immersing the PVA/GO nanocomposites in water. Thus both the plasticizing effect and the competitive hydrogen bonding were the two main reasons for the shape recovery of PVA/GO nanocomposites. This study provides a framework for developing new shape memory polymers (SMPs) and for better understanding the shape recovery mechanism in solvent-induced SMPs.
Co-reporter:Hua Deng, Mizhi Ji, Dongxue Yan, Sirui Fu, Lingyan Duan, Mengwei Zhang and Qiang Fu
Journal of Materials Chemistry A 2014 vol. 2(Issue 26) pp:10048-10058
Publication Date(Web):07 Apr 2014
DOI:10.1039/C4TA01073F
The resistivity–strain behavior of conductive polymer composites (CPCs) has gained intense interest due to its importance for various applications. The resistivity of CPCs often increases substantially and linearly under strain. To achieve constant resistivity under strain, a large filler content and special network configuration are often required. And a tunable step-wise resistivity–strain behavior has yet to be reported. Herein, a new method combining polymer blends and pre-stretching is introduced to modify the resistivity–strain behavior of CPCs based on thermoplastic polyurethane (TPU)/polyolefin elastomer (POE) with multi-walled carbon nanotubes (MWCNTs) selectively incorporated in the TPU phase. Depending on the compositions of blends and the intensity of pre-stretching, various interesting resistivity–strain behaviors have been achieved. The resistivity can be either linearly increasing or constant. Interestingly, two-stepwise resistivity–strain behavior has been achieved, with first an increase then a constant value. To understand this unique phenomenon, the phase morphology and conductive network structure are systematically characterized. It is observed that the orientation of MWCNTs is strongly correlated with overall resistivity. Finally, a mechanism involving fibrillization and “slippage” between conductive phases is proposed to explain the resistivity–strain dependency. This study provides guidelines for the preparation of high performance strain sensors as well as stretchable conductors.
Co-reporter:Lingyan Duan, Sirui Fu, Hua Deng, Qin Zhang, Ke Wang, Feng Chen and Qiang Fu
Journal of Materials Chemistry A 2014 vol. 2(Issue 40) pp:17085-17098
Publication Date(Web):15 Aug 2014
DOI:10.1039/C4TA03645J
The use of conductive polymer composites (CPCs) for strain sensing applications has attracted intense interest lately. The stability and sensitivity of resistivity–strain behaviour are thought to be important issues, but systematic investigations are missing. Herein, the resistivity–strain behavior in terms of stability and sensitivity of CPCs based on poly(styrene-butadiene-styrene) (SBS) containing multiwalled carbon nanotubes (MWCNTs) are studied. It is demonstrated that the preparation method has an important influence on the resistivity–strain behavior of these CPCs. Under linear uniaxial strain, the sensitivity increases with decreasing filler content for both composites, showing higher strain sensitivity near the percolation threshold. Moreover, a higher and wider range of sensitivities is obtained for SBS/MWCNT composites from melt mixing. Under dynamic strain, resistivity downward drifting and shoulder peaks are shown for composites from melt mixing, while linear relationships and reversible resistivity in every cycle are observed for composites from solution mixing, showing good electromechanical consistency, stability and durability. From the TEM, rheology, SEM, SAXS, Raman microscopy and analytical modeling studies, the difference in morphology is thought to be responsible for such resistivity–strain behavior. As more disordered and less densely packed conductive networks in melt-mixed CPCs are more easily destroyed under strain, evenly distributed and densely packed networks in solution mixed CPCs are more stable during cyclic stretching. Finally, human knee motions have been detected using these CPCs, demonstrating a potential application of these CPCs as movement sensors.
Co-reporter:Xiaodong Qi, Guanghui Yang, Mengfan Jing, Qiang Fu and Fang-Chyou Chiu
Journal of Materials Chemistry A 2014 vol. 2(Issue 47) pp:20393-20401
Publication Date(Web):16 Oct 2014
DOI:10.1039/C4TA04954C
A novel, biologically friendly polymer with shape memory and self-healing properties based on poly(propylene carbonate) (PPC)/microfibrillated cellulose (MFC) was prepared. MFC was first modified by a one-step mechanical–chemical approach involving ball milling and esterification reaction. In this way, MFC could be incorporated into PPC at up to 20 wt% with excellent dispersion. The formation of the “MFC network” structure in the PPC matrix was verified by scanning electron microscopy, and the strong interfacial interaction between PPC and MFC was confirmed by X-ray photoelectron spectroscopy. The incorporation of MFC not only significantly enhanced the mechanical strength and thermal stability of the polymer, but also acted as a physical cross-linker that could improve the shape memory property of PPC at specific contents (5–10 wt%). More importantly, due to the shape memory effect and the reinforcement of MFC fibres, the polymer composites also showed enhanced scratch resistance and scratch self-healing behaviour. Our work provides an approach to tune the shape memory behaviours of polymer composites and may contribute to the application of PPC in the field of smart materials.
Co-reporter:Shuangmei Zhang, Hua Deng, Qin Zhang, and Qiang Fu
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 9) pp:6835
Publication Date(Web):April 18, 2014
DOI:10.1021/am500651v
Morphological control of conductive networks involves the construction of segregated or double-percolated conductive networks is often reported to reduce the electrical percolation threshold of conductive polymer composites (CPCs) for better balance among electrical conductivity, mechanical properties, and filler content. Herein, the construction of conductive networks with both segregated and double-percolated characteristics is achieved based on polypropylene (PP)/polyethylene (PE) and multi-wall carbon nanotubes (CNTs). CNTs were firstly dispersed in PE; then PE/CNTs were compounded with PP particles well below the melting temperature of PP. It is observed that the percolation threshold (pc) decreases with increasing PP particle size (size 3.6 mm, pc = 0.08 wt %), which agrees with previous theoretical prediction and experiment in much smaller particle size range. To further study this, the amount of CNTs in PE is varied. It is shown that the degree of PE/CNTs coating on PP particles varies with CNTs as well as PE content in these composites, and have significant influence on the final electrical property. Furthermore, a model combines classical percolation theory and model for segregated network has been proposed to analyze the effect of particle size, degree of coating and thickness of coating on the percolation behavior of these CPCs. In such a model the percolation of CNTs in PE phase as well as PENT phase in the segregated structure can be described. Overall, through such method, a much better balance among mechanical property, conductivity, and filler content is achieved in these CPCs comparing with the results in literature.Keywords: conductive network; conductive polymer composites; electrical percolation; particle size; segregated and double-percolated network;
Co-reporter:Xuelin Yao, Xiaodong Qi, Yuling He, Dongsheng Tan, Feng Chen, and Qiang Fu
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 4) pp:2497
Publication Date(Web):January 29, 2014
DOI:10.1021/am4056694
In the present work, a series of thermoplastic polyurethane (TPU)/microfibrillated cellulose (MFC) nanocomposites were successfully synthesized via in situ polymerization. TPU was covalently grafted onto the MFC by particular association with the hard segments, as evidenced by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis. The adequate dispersion and network structure of MFC in the TPU matrix and the strong interfacial interaction through covalent grafting and hydrogen bonding between MFC and TPU resulted in significantly improved mechanical properties and thermostability of the prepared nanocomposites. The tensile strength and elongation-at-break of the nanocomposite containing only 1 wt % MFC were increased by 4.5-fold and 1.8-fold compared with that of neat TPU, respectively. It was also very interesting to find that the glass transition temperature (Tg) of TPU was decreased significantly with the introduction of MFC, indicating potential for low-temperature resistance applications. Most importantly, compared with TPU nanocomposites reinforced with other nanofillers, the TPU/MFC nanocomposites prepared in this work exhibited excellent transparency and higher reinforcing efficiency.Keywords: covalent grafting; high strength; high toughness; microfibrillated cellulose; thermoplastic polyurethane;
Co-reporter:Hongwei Bai, Huili Liu, Dongyu Bai, Qin Zhang, Ke Wang, Hua Deng, Feng Chen and Qiang Fu
Polymer Chemistry 2014 vol. 5(Issue 20) pp:5985-5993
Publication Date(Web):19 Jun 2014
DOI:10.1039/C4PY00700J
Stereocomplexation between poly(L-lactide) (PLLA) and poly(D-lactide) (PDLA) provides a feasible route for improving the performance of polylactide (PLA), including mechanical strength, thermal stability and hydrolysis resistance. In recent years, several effective methods have been developed to prepare polylactide stereocomplexes (sc-PLA) from commercially available, linear, high-molecular-weight PLLA and PDLA. However, it is still a big challenge to attain pure sc-PLA in the melt-processed products because the prepared sc-PLA has a very poor melt stability, that is the ability to trigger the reformulation of stereocomplex (sc) crystallites after complete melting is significantly depressed, resulting in the formation of mixed homochiral (hc) and sc crystallites. Here we present a facile strategy to fabricate sc-PLA with good melt stability by low-temperature (180 °C) melt-blending of equimolar PLLA and PDLA in the presence of a trace amount (0.1–0.5 wt%) of a cross-linker. During the blending process, sc crystallites form rapidly, followed by a slight cross-linking of PLLA and PDLA chain couples in the mobile amorphous phase, whereas the chain couples in the crystalline phase hardly participate in the cross-linking reaction. The exclusive cross-linking of PLA chains in the amorphous phase not only allows for the introduction of abundant cross-linking points at the ends of the chain couples to prevent them from completely decoupling upon melting but also retains large amounts of long crystallizable PLA segments existing in the initially formed sc crystallites to impart the resulting sc-PLA with an excellent recrystallization ability upon cooling. The formation or reformulation of sc crystallites in the continuous melting and recrystallization process is found to be perfectly reversible, without any trace of hc crystallites.
Co-reporter:Hong Jiang, Li Chen, Songgang Chai, Xuelin Yao, Feng Chen, Qiang Fu
Composites Science and Technology 2014 Volume 103() pp:28-35
Publication Date(Web):28 October 2014
DOI:10.1016/j.compscitech.2014.08.007
Dispersion of graphene nanosheets (GNs) in a polymer matrix as mono layers was an important step towards fabricating high performance polymer/GNs nanocomposites. However, the insoluble and infusible properties of poly (tetrafluoroethylene) (PTFE) made the incorporation of nanofillers in PTFE matrix difficult. In this paper, a novel method based on poly (tetrafluoroethylene) (PTFE) latex that assured the fine dispersion of GNs in PTFE matrix was developed. PTFE latex was first modified by polyethylenimine (PEI) to create the positive charges on the surface of the PTFE particles, and then assembled with negatively charged graphene oxide sheets directly in water through electrostatic interaction, followed with chemical reduction, cold briquetting and hot sintering. Nanocomposites with controllable content and uniformly distributed GNs in PTFE matrix were prepared. The electrostatic coupling interactions improved the dispersion of GNs and facilitated the formation of filler networks in the PTFE matrix. Both the mechanical and wear performance of PTFE/GNs nanocomposites were greatly improved. PTFE/GNs nanocomposites also exhibited excellent electrical properties with a percolation threshold as low as 0.5 wt% and an electrical conductivity of 1.4 S/m at only 2 wt% graphene loadings. The new method agrees well with the latex technical process in PTFE bulk industrial manufacture and paves the way for an environmentally benign process for the bulk production of high quality polymer–graphene nanocomposites.
Co-reporter:Hao Xiu, Yan Zhou, Jia Dai, Chunmei Huang, Hongwei Bai, Qin Zhang and Qiang Fu
RSC Advances 2014 vol. 4(Issue 70) pp:37193-37196
Publication Date(Web):13 Aug 2014
DOI:10.1039/C4RA06836J
A new electric double percolation was realized via carbon black self-networking induced co-continuous like morphology (composed of disconnected PU clusters and bands) in polylactide/poly(ether)urethane (PLA/PU) blends. As a result, a simultaneous improvement in electrical conductivity and impact toughness of the blends without compromising strength and modulus has been achieved.
Co-reporter:Yongsheng Zhao, Bin Su, Licai Zhong, Feng Chen, and Qiang Fu
Industrial & Engineering Chemistry Research 2014 Volume 53(Issue 39) pp:15287-15295
Publication Date(Web):September 5, 2014
DOI:10.1021/ie5022514
In this work, a poly(styrene-b-isoprene-b-styrene) thermoplastic elastomer was processed via a novel processing technique, dynamic-packing injection molding (DPIM). The shear cessation time is variable during DPIM, and a conventional injection-molded sample (C-sample) was prepared for comparison. For the dynamic-packing injection-molded sample (D-sample) with a short cessation time, a high Young’s modulus was obtained but with no significant enhancement of the break strength relative to the C-sample. However, a significant improvement of the break strength was achieved for the D-sample with longer cessation time. The mechanical performance of both the C-sample and D-samples was interpreted from the contribution of polyisoprene (PI, as the matrix) and polystyrene (PS, as a dispersed phase) segments. It is proposed that a short cessation time (strong shear) can induce the formation of a stretched PI network, while prolonged cessation time (more relaxation) could result in the segregation of PS and PI microdomains and the formation of a perfect parallel orientation of the PS cylinder in a hexagonal lattice.
Co-reporter:Zhen Li, Yunjie Shi, Huili Liu, Feng Chen, Qin Zhang, Ke Wang and Qiang Fu
RSC Advances 2014 vol. 4(Issue 85) pp:45234-45243
Publication Date(Web):03 Sep 2014
DOI:10.1039/C4RA06548D
PP fiber reinforced olefin block copolymers (OBCs) were manufactured in this research. Chopped PP fibers were first compounded with OBCs at a fixed ratio in a Haake mixer at 140 °C (lower than the melting point of PP fiber). The blends were then processed at three different temperatures, below (155 °C), around (170 °C) and above (190 °C) the melting temperature of the fibers. The three specimens displayed completely different mechanical properties according to the following sequence: 170 °C > 190 °C > 155 °C. To obtain an insight into the phenomenon, the structure–property relationships were fully investigated. It was found that when the blends were processed at 155 °C, the fibers retained a high strength and modulus but lost the interaction with the matrix, displaying poor mechanical properties. At a higher temperature of 190 °C, the fiber showed a strong interaction with OBCs but the reinforcing effect was unsatisfactory because the melted fibers lost the original modulus. When the blends were injection molded at 170 °C, the fibers were in the partially melted state, showing strong interaction with the matrix and relatively high strength and modulus. Therefore, the composites exhibited the mechanical performance. This article proves that the fiber strength and interfacial bonding are the two factors that determine the final properties in fiber reinforced composites. Moreover, it is suggested that the interfacial interaction could be improved by controlling the melting state instead of complex surface treatment of the fibers.
Co-reporter:Songjia Han;Kun Ren;Chengzhen Geng;Ke Wang;Qin Zhang;Feng Chen
Polymer International 2014 Volume 63( Issue 4) pp:646-651
Publication Date(Web):
DOI:10.1002/pi.4551
Abstract
Bioresource natural sisal fiber (SF) was used to prepare single fiber-reinforced isotactic polypropylene (iPP) composites. Three kinds of interfacial crystalline morphologies, spherulites, medium nuclei density transcrystallinity (MD-TC) and high nuclei density transcrystallinity (HD-TC), were obtained in the single fiber-reinforced composites by implementing quiescent or dynamic shear-enhanced crystallization and by modulating the compatibility interaction between SF and iPP. The development of interfacial shear strength (IFSS) during the interfacial crystallization process was demonstrated for the first time using a combination of single-fiber fragmentation testing and optical microscope observation. A close correlation between IFSS and morphological characteristics of interfacial crystallization was well elucidated. The increases in IFSS were very different for spherulitic, MD-TC and HD-TC morphologies. The highest IFSS obtained was 28 MPa, after the formation of HD-TC, which was about 62% of the tensile strength of neat iPP (45 MPa). These results offer powerful and direct evidence that interfacial crystallization could play an important role in the enhancement of interfacial adhesion of real SF/iPP composites. © 2013 Society of Chemical Industry
Co-reporter:Yu-han Li;Mi Zhou;Cheng-zhen Geng;Feng Chen 陈枫
Chinese Journal of Polymer Science 2014 Volume 32( Issue 12) pp:1724-1736
Publication Date(Web):2014/12/01
DOI:10.1007/s10118-014-1518-6
Inspired by the photoprotection, radical scavenging of melanin together with versatile adhesive ability of mussel proteins, polydopamine (PDA) nanoparticles were successfully prepared and incorporated into environmentally friendly polymer, poly(propylene carbonate) (PPC) via solvent blending. The prepared composites exhibited excellent thermal stability in air and nitrogen atmosphere and extraordinary mechanical properties. The composites displayed eminent increase of temperature at 5% weight loss (T5%) by 30–100 K with 0.3 wt%–2.0 wt% loadings, meanwhile, the tensile strength and Young’s modulus were significantly improved from 11.5 MPa and 553.7 MPa to 40.5 MPa and 2411.2 MPa, respectively. The kinetic calculation indicated that improvement of T5% is presumably derived from suppressing chain-end unzipping. The glass transition temperature (Tg) of the PPC/PDA composites increased by 8–10 K. This is probably due to hydrogen bonding interaction since the abundant proton donors along PDA chains would interact with proton acceptors like C=O and C-O-C in PPC which would cause restriction of segmental motion of PPC chains.
Co-reporter:Hongwei Bai, Chunmei Huang, Hao Xiu, Qin Zhang, Hua Deng, Ke Wang, Feng Chen, and Qiang Fu
Biomacromolecules 2014 Volume 15(Issue 4) pp:
Publication Date(Web):March 11, 2014
DOI:10.1021/bm500167u
Recently, some attempts have been made to enhance the gas barrier properties of semicrystalline polymers by precisely controlling the arrangement of their impermeable crystalline lamellae. However, it is still a great challenge to achieve regular arrangement of the lamellae along the direction perpendicular to the gas diffusion path, especially using conventional polymer processing technologies. This work presents a novel and simple strategy to dramatically improve oxygen barrier performance of biobased and biodegradable polylactide (PLA) through constructing parallel-aligned shish-kebab-like crystals with well-interlocked boundaries with the aid of a highly active nucleating agent. The nucleating agent was introduced into PLA by melting compounding and the sheet-like specimens were fabricated by compression molding. We demonstrate that the fibrillar nucleating agent dispersed in PLA melt can serve as shish to induce the change of crystallization habit of PLA from isotopic spherulitic crystals to unique shish-kebab-like crystals and the shear flow in the compression molding can induce the highly ordered alignment of the nucleating agent fibrils as well as the subsequent shish-kebab-like crystals along the direction parallel to the sheet surface. More importantly, the growing lamellae are found to interpenetrate and tightly interlock with each other at the boundary regions of the shish-kebab-like crystals in the later stage of the crystallization, forming a densely packed nanobrick wall structure to prevent gas molecules from permeating through the crystals and thus imparting the PLA sheets with unprecedentedly low oxygen permeability. This work provides not only a successful example of preparing semicrystalline polymer with super gas barrier properties by tailoring crystal superstructure but also a promising route to rapidly fabricate high-performance food packaging materials via industrially meaningful melt processing.
Co-reporter:Cheng-zhen Geng;Yan-ling Zhu;Guang-hui Yang
Chinese Journal of Polymer Science 2014 Volume 32( Issue 1) pp:9-20
Publication Date(Web):2014 January
DOI:10.1007/s10118-014-1382-4
In this work, polypropylene (PP)/octene-ethylene copolymer (POE) blends were injection-molded using the socalled dynamic packing injection technique, which imposed oscillatory shear on the gradually cooling melt during the packing solidification stage. In this way, the effect of shear on the size distribution and anisotropy of the minor phase droplets could be investigated. Besides, by using two kinds of POE with different octene contents, the effect of component miscibility was also studied. The results show that the droplet size is mainly determined by composition and miscibility, and droplet anisotropy is mainly determined by droplet size and shear. Most importantly, under the same processing condition, droplet anisotropy increases with droplet size, and there seems a linear fit between them, disregarding the miscibility factor. These results may provide guidance for preparing polymer blends with desired properties by tailoring their phase morphologies.
Co-reporter:Yao Gao;Gui-ying Zong;Hong-wei Bai 傅强
Chinese Journal of Polymer Science 2014 Volume 32( Issue 2) pp:245-254
Publication Date(Web):2014 February
DOI:10.1007/s10118-014-1397-x
The combined effects of stretching and single-walled carbon nanotubes (SWCNTs) on crystalline structure and mechanical properties were systematically investigated in melt-spun polypropylene (PP) fibers prepared at two different draw ratios. The dispersion, alignment of the SWCNT bundles and interfacial crystalline structure in the composite fibers are significantly influenced by the stretching force during the melt spinning. The nanohybrid shish kebab (NHSK) superstructure where extended PP chains and aligned SWCNT bundle as hybrid shish and PP lamellae as kebab has been successfully obtained in the composite fibers prepared at the high draw ratio and the related formation mechanism is discussed based on the results of morphological observations and 2d-SAXS patterns. Large improvement in tensile strength and modulus has been realized at the high draw ratio due to the enhanced orientation and dispersion of SWCNT bundles as well as the formation of NHSK.
Co-reporter:Tian-xiang Jin;Mi Zhou;Shao-dong Hu;Feng Chen
Chinese Journal of Polymer Science 2014 Volume 32( Issue 7) pp:953-960
Publication Date(Web):2014 July
DOI:10.1007/s10118-014-1463-4
Poly(butylene succinate) (PBS) with different molecular weight was synthesized from 1, 4-butanediol and succinic acid by direct melt condensation. The synthesized PBS was identified by 1H-NMR and FTIR spectrometry. The molecular weight was calculated from the intrinsic viscosity, and its value was between 20000 and 70000. The crystallization behavior and crystal morphology as function of molecular weight were investigated by DSC and PLM, respectively. The mechanical properties and hydrolytic degradation behaviors related with change of molecular weight were also studied in this work. The results demonstrated that the properties of PBS were determined by both molecular weight and crystallization properties (crystallinity as well as crystal morphology). Our work is important for the design and preparation of PBS with proper molecular weight for its practical application.
Co-reporter:Shuang-mei Zhang;Hui-xian Zhang;Wei-yi Zhang
Chinese Journal of Polymer Science 2014 Volume 32( Issue 7) pp:823-833
Publication Date(Web):2014 July
DOI:10.1007/s10118-014-1474-1
In this study, four hydroxyl-terminated polydimethylsiloxanes (PDMSOH) with different viscosities and hydroxyl contents were used to improve the toughness of polycarbonate (PC) through reactive melt blending. A largely improved toughness of PC has been achieved, and the low temperature toughness of PC/PDMSOH blends could overtake that of PC homopolymer in much higher temperatures (e.g. −10 °C versus 23 °C). Moreover, it was found that the more the hydroxyl content, the less the PDMSOH was needed to reach the highest toughness, suggesting that equivalent molar ratio between the carbonyl group content of PC and the hydroxyl group content of PDMSOH was required for the toughening of PC. Ultraviolet spectrophotometry was used to analyze the possible reaction between PC and PDMSOH. Contact angle was measured to assess the change of interfacial interaction between PC and PDMSOH as change of viscosity and hydroxyl content. The formation of PC-co-PDMSOH copolymer was believed to be the key for the toughening effect. This work gives a profound recommendation of the optimum kind and dosage of PDMSOH which should be used to improve the toughness of PC and will find immediate industrial applications.
Co-reporter:Chengzhen Geng, Guanghui Yang, Hongwei Bai, Yuhan Li, Qiang Fu, Hua Deng
The Journal of Supercritical Fluids 2014 Volume 87() pp:83-92
Publication Date(Web):March 2014
DOI:10.1016/j.supflu.2014.01.003
•ScCO2-assisted annealing was adopted to toughen polypropylene for the first time.•Polypropylene with well-balanced mechanical properties was prepared.•Polypropylene random copolymer with superior toughness was prepared.•Toughening mechanism of scCO2-assisted annealing was proposed.A supercritical carbon dioxide (scCO2) assisted annealing technique is adopted to toughen polypropylene (PP) and its random copolymer with 3.8 wt% co-monomer content (PPR). By using this technique, PP with 4-time improvement in toughness or PPR with superior toughness are obtained. Meanwhile, the stiffness of the materials could be maintained. To understand the toughening mechanism, scanning electron microscope, wide angle X-ray diffraction, calorimetry, dynamic mechanical analysis and small angle X-ray scattering characterizations are carried out. It is demonstrated that the toughening mechanism is strongly related to the microstructure evolutions, including decreased chain density in the mobile amorphous phase, improved crystalline phase and improved rigid amorphous phase after annealing. These microstructure changes could result in higher cavitation ability and diminish inner stress in the amorphous phase, which consequently favors improvement in toughness.
Co-reporter:Jinrong Wu, Hui Li, Siduo Wu, Guangsu Huang, Wang Xing, Maozhu Tang, and Qiang Fu
The Journal of Physical Chemistry B 2014 Volume 118(Issue 8) pp:2186-2193
Publication Date(Web):January 30, 2014
DOI:10.1021/jp410604a
Oleic acid modified iron oxide nanoparticles (IONs) with different sizes were synthesized and mixed with styrene-butadiene-styrene block copolymer (SBS) with a lamellar structure. The octadecene segments on the oleic acid molecules have chemical affinity with the polybutadiene (PB) blocks, which makes IONs tend to be selectively confined in the microphase-separated PB domains. However, the dispersion state strongly depends on the ratio of the particle diameter (d) to the lamellar thickness (l) of the PB domains, which further changes the phase separation of SBS. When d/l ∼0.5, most of IONs are concentrated in the middle of the PB layers at low particle loading. Upon increasing the particle loading, part of IONs contact each other to form long strings due to their strong magnetic interactions. Away from the strings, IONs are either selectively dispersed in the middle and at the interfaces of the PB domains, or randomly distributed at some regions in which the phase separation of SBS is suppressed. The phase separation of SBS transforms from the lamellar structure to a cylinder structure when the IONs loading is higher than 16.7 wt %. As d is comparable to l, IONs aggregate to form clusters of 100 to 300 nm in size, but within the clusters IONs are still selectively dispersed in the PB domains instead of forming macroscopic phase separation. It is interpreted in terms of the relatively small conformational entropy of the middle blocks of SBS; thus, incorporation of nanoparticles does not lead to much loss of conformational entropy. Although incorporation of IONs with d/l ∼1 significantly increases the interfacial curvature and roughness, it has less influence on the phase separation structure of SBS due to the inhomogeneous dispersion. When d is larger than l, IONs are macroscopically separated from the SBS matrix to form clusters of hundreds of nanometers to several micrometers. More interestingly, the phase separation of SBS transforms from the lamellar structure to a two-phase co-continuous structure, probably due to the rearrangement of SBS molecules to cover the clusters with PB segments and the strong magnetic interaction exerting additional force on the SBS matrix during the evaporation of the solvent and the subsequent thermal annealing process.
Co-reporter:Mi Zhou, Shuman Xu, Yuhan Li, Chao He, Tianxiang Jin, Ke Wang, Hua Deng, Qin Zhang, Feng Chen, Qiang Fu
Polymer 2014 Volume 55(Issue 13) pp:3045-3053
Publication Date(Web):13 June 2014
DOI:10.1016/j.polymer.2014.05.013
The key for fiber reinforced polymer composites is the interfacial interaction between fiber and polymer matrix. The crystallization of polymer on the surface of fiber as a possible way to enhance the interfacial interaction has received increasingly attention. In this work, the transcrystalline (TC) formation and properties of isotactic polypropylene (iPP) on ramie fiber surface, as induced either by fiber pulling or by dopamine modification, were investigated and compared. It was found that the growth rate of shear induced TC is faster than that obtained via dopamine modification. There exists α–β crystal form transition in the TC formation process as induced by pulling while only α-crystal form is obtained via dopamine modification. By using both dopamine modification and fiber pulling, a formation of TC with two step growth was observed for the first time: the first step growth has much enhanced rate than that induced by fiber pulling, and second step growth has the same rate with that induced by dopamine modification. Thus a unique TC structure was obtained, with α-crystal form presented in the inner layer and the outer layer, and β-crystal form in between. The result from single fiber fragmentation test indicated that interfacial shear stress (IFSS) between iPP and ramie fiber for dopamine modification induced TC is much higher than that of shear induced TC. Our work provides guidance for the preparation of polymer/fiber composites with enhanced interfacial interaction via formation of TC layer by using shear or fiber surface modification.
Co-reporter:Hao Xiu, Chunmei Huang, Hongwei Bai, Jia Jiang, Feng Chen, Hua Deng, Ke Wang, Qin Zhang, Qiang Fu
Polymer 2014 Volume 55(Issue 6) pp:1593-1600
Publication Date(Web):24 March 2014
DOI:10.1016/j.polymer.2014.01.057
Obtaining network-like morphology (rubber particles are unevenly distributed in the matrix, forming a discontinuous rubber network structure) has been considered to be an effective strategy to optimize the toughness of rubber-toughened polymers. However, it is very difficult to achieve using conventional processing method. In this work, taking elastomer-toughened polylactide (PLA) as an example, we attempt to use hydrophilic silica (SiO2) nanoparticles with self-networking capability to control the phase morphology and the mechanical properties of PLA/poly(ether)urethane (PU) (85/15) blend. It is interesting to find that the selective localization of SiO2 nanoparticles in the PU phase and at the phase interface induces the morphological change from a common sea-island structure to a unique network-like structure constructed by discrete PU particles with irregular shapes, thus giving rise to a remarkable improvement in the impact toughness of the blend with strength and modulus unaffected. The formation of the network-like structure is attributed to the synergistic effect between the self-networking of the interface-localized SiO2 and the enhanced elasticity of the SiO2-localized PU phase. This inspiring result proves the introduction of nanoparticles with self-networking capability into polymers blends to be a universal platform to design their performance via tuning the phase structure.
Co-reporter:Meng Wu, Zhiqiang Wu, Ke Wang, Qin Zhang, Qiang Fu
Polymer 2014 Volume 55(Issue 24) pp:6409-6417
Publication Date(Web):18 November 2014
DOI:10.1016/j.polymer.2014.10.004
•Dramatic increase of toughness in biodegradable polymer, PLA.•Addition of low content of OBC elastomer results in good supertough-strength balance.•The crucial roles of interfacial compatibility and thermodynamically stable morphology.•Towards elastomer-toughened biodegradable polymer with high performance.For the toughening of thermoplastics by using elastomeric components, the relatively high contents of elastomeric phase are commonly demanded to trigger the brittle-to-ductile transition. However, an obvious drawback of remarkably decreased strength and rigidity may arise after incorporation of large amount of elastomeric species. The main thinking in our present work is to achieve a good toughness-strength balance in an elastomer-toughened thermoplastic system with less amount of elastomeric phase, i.e., the blend of poly(lactic acid) (PLA)/olefin block copolymer (OBC) 90/10 w/w. When both of the thermodynamics favorable compatibility and the thermodynamically stable morphology were realized, the impact toughness of PLA/OBC 90/10 blend was 25 multiples for that of pure PLA, while the tensile strength could preserve as a level of 87% (based on the value of pure PLA). The interfacial compatibilization between PLA and OBC achieved through adding EMA-GMA as a compatibilizer. On the other hand, a quiescent annealing process at 90 °C resulted in a more thermodynamically stable morphology, which was characterized as high crystallinity, large size of elastomer-phase droplet, and thickening interfacial layer. Our study offers new insight into the optimization of properties of multicomponent blend that except for realizing the thermodynamics favorable compatibility, the transition from kinetics-dominated morphology to thermodynamically stable one also plays a crucial role.
Co-reporter:Hongwei Bai, Chunmei Huang, Hao Xiu, Qin Zhang, Qiang Fu
Polymer 2014 Volume 55(Issue 26) pp:6924-6934
Publication Date(Web):15 December 2014
DOI:10.1016/j.polymer.2014.10.059
•Nucleating agent was used as a robust template to tailor the crystal superstructure.•PLA injection-molded bars with highly orientated lamellae were prepared.•Effect of crystal superstructure on the mechanical properties of PLA was studied.•Lamellae orientation imparts the bars with greatly improved mechanical properties.•We provide a guideline for preparing high-performance PLA injection-molded articles.The performance of semicrystalline polymers is significantly dependent on the crystal morphology and lamellae orientation. In this work, the crystal superstructure and mechanical properties of polylactide (PLA) with different amounts of nucleating agent (tetramethylene-dicarboxylic dibenzoyl-hydrazide, TMC-306) were investigated. It was found that TMC-306 can be dissolved in PLA melt and re-crystallize into fibrils upon cooling. These fibrils can serve as nucleation templates to induce the crystallization of PLA on their surface, resulting in a large enhancement in crystallization rate. More importantly, PLA lamellae can grow perpendicular to the long axis of TMC-306 fibrils, inducing the formation of shish-calabash, shish-kebab and needle-like structures, depending on the concentration of TMC-306 used. Taking advantage of shear flow experienced in injection molding, TMC-306 fibrils tend to align in PLA melt along the shear flow direction, inducing the formation of highly orientated PLA lamellae in injection-molded articles. In this way, a simultaneous improvement in impact toughness, tensile strength and elongation at break is achieved. This work provides a good example of using a fibrous nucleating agent as a template to tailor the crystal morphology and lamellae orientation, thus achieving greatly enhanced properties for PLA.
Co-reporter:Li Chen, Yuling He, Songgang Chai, Hong Qiang, Feng Chen and Qiang Fu
Nanoscale 2013 vol. 5(Issue 13) pp:5809-5815
Publication Date(Web):23 Apr 2013
DOI:10.1039/C3NR01083J
Two-dimensional graphene and graphene-based materials have attracted tremendous interest, hence much attention has been drawn to exploring and applying their exceptional characteristics and properties. Integration of graphene sheets into macroscopic fibers is a very important way for their application and has received increasing interest. In this study, neat and macroscopic graphene fibers were continuously spun from graphene oxide (GO) suspensions followed by chemical reduction. By varying wet-spinning conditions, a series of graphene fibers were prepared, then, the structural features, mechanical and electrical performances of the fibers were investigated. We found the orientation of graphene sheets, the interaction between inter-fiber graphene sheets and the defects in the fibers have a pronounced effect on the properties of the fibers. Graphene fibers with excellent mechanical and electrical properties will yield great advances in high-tech applications. These findings provide guidance for the future production of high performance graphene fibers.
Co-reporter:Lin Lin, Siyao Liu, Qi Zhang, Xiaoyu Li, Mizhi Ji, Hua Deng, and Qiang Fu
ACS Applied Materials & Interfaces 2013 Volume 5(Issue 12) pp:5815
Publication Date(Web):May 28, 2013
DOI:10.1021/am401402x
The use of conductive polymer composites (CPCs) as strain sensors has been widely investigated and various resistivity-strain sensitivities are desirable for different applications. In this study, the use of mixed carbon fillers and functionalized carbon nanotubes was demonstrated to be vital for preparing thermoplastic polyurethane (TPU)-based strain sensors with tunable sensitivity. To understand the strain sensing behavior, we carried out scanning electron microscopy (SEM), Raman spectroscopy, wide-angle X-ray diffraction (WAXD), mechanical test, and rheology-electrical measurement. Hybrid fillers of multi-walled carbon nanotubes (MWNTs) and carbon black (CB) could reduce the entanglement in conductive network structure, thus increase the resistivity-strain sensitivity. Furthermore, incorporation of additional functionalized MWNTs in the CPCs could enhance the interfacial interaction between nanofillers and TPU, leading to further increase in sensitivity. Through such a simple method, strain sensors could be efficiently fabricated with large strain-sensing capability (strain as large as 200%) and a wide range of strain sensitivity (gauge factor ranging from 5 to 140238). Finally, the exponential revolution of resistive response to strain was fitted with a model based on tunneling theory by Simmons. It was observed that the change in tunneling distance and the number of conductive pathways could be accelerated significantly by adjusting conductive network structure and interfacial interaction. This study provides a guideline for the preparation of high-performance CPC strain sensors with a large range of resistivity-strain sensitivity.Keywords: conductive polymer composite; interfacial interaction; network structure; sensitivity; strain sensor;
Co-reporter:Li Lin;Hua Deng;Xiang Gao;Shuangmei Zhang;Emiliano Bilotti;Ton Peijs
Polymer International 2013 Volume 62( Issue 1) pp:134-140
Publication Date(Web):
DOI:10.1002/pi.4291
Abstract
Eutectic metal particles and carbon nanotubes are incorporated into a thermoplastic polyurethane matrix through a simple but efficient method, melt compounding, to tune the resistivity–strain behavior of conductive polymer composite (CPC) fibers. Such a combination of conductive fillers is rarely used for CPCs in the literature. To characterize the strain-sensing properties of these fibers, both linear and dynamic strain loadings are carried out. It is noted that a higher metal content in the fibers results in higher strain sensitivity. These strain-sensing results are discussed through a morphological study combined with a model based on the classic tunneling model of Simmons. It is suggested that a high tunneling barrier height is preferred in order to achieve higher strain sensitivity. Copyright © 2012 Society of Chemical Industry
Co-reporter:Yanling Zhu;Feng Luo;Hongwei Bai;Ke Wang;Hua Deng;Feng Chen;Qin Zhang
Journal of Applied Polymer Science 2013 Volume 129( Issue 6) pp:3613-3622
Publication Date(Web):
DOI:10.1002/app.39107
Abstract
In this work, the synergistic effects of β-modification and impact polypropylene copolymer (IPC) on brittle–ductile (B–D) transition behavior of polypropylene random copolymer (PPR) have been investigated. It is interesting to find that adding both IPC and β-nucleating agent into PPR has three effects: (i) leading to a significant enhancement in β-crystallization capability of PPR, (ii) contributing to the shift of B–D transition to lower temperatures, (iii) increasing the B–D transition rate. The reason for these changes can be interpreted from the following two aspects. On one hand, the transition of crystalline structure from α-form to β-form reduces the plastic resistance of PPR matrix, thus causing the initiation of matrix shear yielding much easier during the impact process. On the other hand, the well dispersed rubbery phase in IPC with high molecular mobility at relatively low temperatures is beneficial to the shear yielding of PPR matrix and, subsequently, the great improvement in impact toughness of the ternary blends. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Co-reporter:Feng Luo;Chenlong Xu;Nanying Ning;Ke Wang;Hua Deng;Feng Chen
Polymer International 2013 Volume 62( Issue 2) pp:172-178
Publication Date(Web):
DOI:10.1002/pi.4273
Abstract
The phase morphology and toughening behavior of impact polypropylene copolymer (IPC) with and without nucleating agent (NA), prepared at different processing melt temperatures (Tp), were investigated. Interestingly, three different structures can be formed in the IPC samples by adding NA or tuning Tp. A well-defined core–shell structure is obtained in samples with α-NA or without NA prepared at all Tp. A developing multilayered structure is mainly formed at high Tp with added β-NA, while an incomplete phase separation structure with interpenetrating chains is the dominant structure for IPC samples prepared at low Tp with added β-NA. In this case, because of the synergistic effect between phase morphology and relatively high β-form crystal content, the chain interaction among the components and chain mobility of the amorphous portion of IPC are distinctly improved, resulting in a largely improved toughness under 0 °C. This improvement in toughness is very important for applications. © 2012 Society of Chemical Industry
Co-reporter:Chaoqun Li;Guanghui Yang;Hua Deng;Ke Wang;Qin Zhang;Feng Chen
Polymer International 2013 Volume 62( Issue 7) pp:1077-1084
Publication Date(Web):
DOI:10.1002/pi.4394
Abstract
In this work, polystyrene (PS)/functionalized graphene nanocomposite foams were prepared using supercritical carbon dioxide. Thermally reduced graphene oxide (TRG) and graphene oxide (GO) were incorporated into the PS. Subsequently, the nanocomposites were foamed with supercritical CO2. The morphology and properties of the nanocomposites and the nucleation efficiency of functionalized graphene in foaming PS are discussed. Compared with GO, TRG exhibited a higher nucleation efficiency and more effective cell expansion inhibition thanks to its larger surface area and better exfoliated structure. It is suggested that the factors that have a significant influence on the nucleation efficiency of TRG and GO originate from the differences in surface properties and chemical structure. Furthermore, PS/TRG nanocomposites and their nanocomposite foams also possess good electrical properties which enable them to be used as lightweight functional materials.© 2012 Society of Chemical Industry
Co-reporter:Qinna Zhao, Yu Ding, Biao Yang, Nanying Ning, Qiang Fu
Polymer Testing 2013 Volume 32(Issue 2) pp:299-305
Publication Date(Web):April 2013
DOI:10.1016/j.polymertesting.2012.11.012
A unique ultrafine full-vulcanized powdered ethyl acrylate rubber (EA-UFPR) was used as the toughening modifier for poly (lactic acid) (PLA). Largely improved tensile toughness was successfully achieved with the incorporation of only 1 wt% EA-UFPR, while the tensile strength and modulus of the blends were almost the same as pure PLA. The highly efficient toughening of PLA by UFPR is mainly ascribed to the strong interfacial interaction between PLA and UFPR and good dispersion of UFPR particles in PLA matrix. Our work provides an effective toughening method to largely improve the mechanical properties of PLA without sacrificing its stiffness, which is very important for the wide application of PLA materials.
Co-reporter:Jianchuan Wang, Tiannan Zhou, Hua Deng, Feng Chen, Ke Wang, Qin Zhang, Qiang Fu
Colloids and Surfaces B: Biointerfaces 2013 Volume 101() pp:171-176
Publication Date(Web):1 January 2013
DOI:10.1016/j.colsurfb.2012.06.008
In this paper, reduced graphite oxide (RGO) was prepared using thiourea dioxide as reductant and polyvinylpyrrolidone (PVP) as stabilizer. Thiourea dioxide, a cheap and nontoxic industrialized material, was demonstrated to be an efficient reducing agent for graphite oxide (GO) in this paper. Ultraviolet and visible (UV–vis) spectroscopy results revealed that the reduction of GO could be readily achieved in 10 min, a reaction time which is much shorter than those required in common reduction reactions. The procedures of reduction including the by-products are all nontoxic, thus it is absolutely environmentally friendly. To the best of our knowledge, this is the first time that thiourea dioxide was successfully used to prepare RGO. Moreover, the stabilizer, PVP, which could be easily absorbed onto the surface of RGO, provided RGO with good water and organic solvents solubility, with low conductivity though. However, by controlling the content of PVP, RGO with balanced solubility and conductivity can be obtained. The resultant RGO could be used as nanofillers to prepare conductive materials and biomaterials with potential applications as electrical devices or biosensors.Graphical abstractHighlights► Thiourea dioxide is reported to reduce graphite oxide for the first time.► Reduction procedure is quite fast and absolutely environmentally friendly.► Polyvinylpyrrolidone (PVP) is used to stabilize the reduced graphite oxide.► Influences of PVP loading on re-dispersion, thickness and conductivity of graphene are studied.
Co-reporter:Jinwen Wang;Meng Wu;Yuhan Li;Feng Luo;Feng Chen
Journal of Materials Science 2013 Volume 48( Issue 5) pp:1932-1939
Publication Date(Web):2013 March
DOI:10.1007/s10853-012-6958-1
A simple and effective method to add large amounts of expanded graphite (EG) to poly (phenylene sulfide) (PPS) was developed. Before conventional melt processing, solid-state PPS and EG powders were mixed using high-speed rotation. In this way, the loose and porous vermicular structure of EG could be effectively destroyed and partly exfoliated, which made EG easy to be adsorbed on the surface of the PPS powders. This was extraordinarily helpful to achieve good dispersions of EG during the subsequent melt mixing even at high loading, which was difficult to achieve by conventional direct melt mixing. As a result of the good dispersions and strong interactions, the EG/PPS composites prepared showed a dramatically improved thermal conductivity (15.8 Wm−1K−1) and electrical conductivity (125.3 Sm−1) as the addition of EG reached 60 wt%.
Co-reporter:Xiuyun Li;Ke Wang
Polymer Engineering & Science 2013 Volume 53( Issue 10) pp:2053-2060
Publication Date(Web):
DOI:10.1002/pen.23467
In this study, a water-soluble crystallizable polymer, poly(ethylene glycol) (PEG), was compounded with isotactic polypropylene (iPP), and a subsequent thermo-annealing process was added to improve the toughness of iPP/PEG blend. By adding a small amount of PEG (5 wt%) into iPP, only a mild increment of 40% in toughness was achieved. However, the toughness of iPP/PEG (95/5) blend could be improved remarkably when the postprocessing procedure, thermal annealing, was utilized. For example, the notched impact strength of iPP/PEG blend annealed under 120°C for 12 h was five times of that of neat iPP. In addition, the tensile strength of annealed blend was slightly changed, compared with neat iPP. To ascertain the origin of toughening, various crystallographic and morphological/structural characterizations, including X-ray diffraction, electron microscopy, and calorimeter were employed. A specific structural change, in which more and more amounts of micrometer/sub-micrometer voids, yielded within the amorphous iPP region during the annealing process, was responsible for the prominent toughening behavior. POLYM. ENG. SCI., 53:2053–2060, 2013. © 2013 Society of Plastics Engineers
Co-reporter:Juan-juan Su;Guang-hui Yang;Tian-nan Zhou;Xiang Gao
Colloid and Polymer Science 2013 Volume 291( Issue 4) pp:911-917
Publication Date(Web):2013 April
DOI:10.1007/s00396-012-2809-5
A compound additive system consisting of expanded graphite (EG) and poly(ethylene glycol) (PEG) was designed to enhance the crystallization of poly(ethylene terephthalate) (PET). In this additive system, EG acted as a heterogeneous nucleating agent to reduce energy barrier for nucleation, while PEG played as plasticizer to improve mobility of PET chains. Simultaneously adding EG and PEG resulted in faster crystallization kinetics than the cases of solely adding EG or PEG in both of non-isothermal and isothermal crystallization processes, indicating a synergistic effect of EG and PEG on enhancing PET crystallization. However, for non-isothermal crystallization process, in which crystallization occurred from a cooling melt, EG played a dominant role. As to isothermal crystallization process where crystallization took place in a super-cooling state, PEG seemed to be more important. Moreover, the chain conformation change among the semi-crystalline PET specimens was ascertained by Fourier transform infrared spectroscopy.
Co-reporter:Lei Bi;Jin-wen Wang;Feng Chen 陈枫 傅强
Chinese Journal of Polymer Science 2013 Volume 31( Issue 11) pp:1546-1553
Publication Date(Web):2013 November
DOI:10.1007/s10118-013-1345-1
Two kinds of poly(vinyl alcohol) (PVA)-silica composites were prepared with different methods. One composite was prepared by directly mixing PVA with 80 nm silica nano-particles which were made from tetraethoxysilane (TEOS). The another was obtained by the mixing PVA and hydrolyzed TEOS in the presence of acid-catalyst. The properties of the two PVA/silica hybrids were characterized by means of scanning electron microscopy (SEM), UV-Visible spectroscopy, solubility tests, limiting oxygen index (LOI) test, tensile test and dynamical mechanical analysis (DMA), respectively. The results indicate that PVA-TEOS composites (PT for short) display more transparency than PVA-silica nano-particles hybrids (PS for short). At the same time, The PT composites presented more excellent performance than PS in water resistance, fire resistance and mechanical properties. Moreover, the Tg of PT increased with increasing TEOS content, while that of PS decreased.
Co-reporter:Nan Li;Wei Cheng;Kun Ren;Feng Luo;Ke Wang 王柯
Chinese Journal of Polymer Science 2013 Volume 31( Issue 1) pp:98-109
Publication Date(Web):2013 January
DOI:10.1007/s10118-013-1204-0
In this study, good dispersion status of graphite in a nonpolar, intractable polymer, i.e. polypropylene (PP), was realized in melt processing by using a specific dynamic packing injection molding (DPIM) technique. The exfoliation extent of graphite increased remarkably from the skin zone to the core zone of the molded part, as confirmed by combination of WAXD, SEM and TEM analyses, indicating an accelerated exfoliation occurred during the DPIM processing. This phenomenon is due to decreased melt flow channel and increased melt viscosity as the solidification takes place from the wall into the center, which leads to greatly increased shear force. The good dispersion of graphite results in obvious reinforcements of both tensile strength and impact strength by adding moderate amount of graphite. The present study proposes a promising route for realizing the large-scale fabrication of structural parts of polymer/exfoliated-graphite nanocomposites with excellent mechanical properties.
Co-reporter:Zhoukun He;Xiaorong Lan;Feng Chen;Ke Wang
Journal of Coatings Technology and Research 2013 Volume 10( Issue 5) pp:641-647
Publication Date(Web):2013 September
DOI:10.1007/s11998-013-9490-6
Water droplets or films which are formed according to surface wettability show different effects on surface transparency. The effects of surface wettability on transparency in different water conditions are worth investigating because the surface usually suffers from the variable environmental water conditions. Herein, superhydrophobic and superhydrophilic surfaces, with negligible differences of physical structure but great differences of chemical composition, are used to investigate for the first time the relationship between surface wettability and transparency in four water conditions, including ambient condition, liquid water, boiling water steam, and ambient conditions after freezing at −4°C for 1 week. The transparency of the superhydrophobic surface is only about 5% lower in 550 nm light wavelength than that of the superhydrophilic surface in ambient conditions, but it is about 24% lower than that of the superhydrophilic surface in liquid water. When the surfaces are exposed to boiling water steam and ambient conditions after freezing at −4°C for 1 week, the superhydrophobic surface also shows lower transparency than the superhydrophilic surface because of increased fogging. However, the transparency shows little difference when the fog evaporates completely. The relationship revealed between surface wettability and transparency in different water conditions will be beneficial in choosing suitable wettability surfaces to satisfy the needed transparency in actual applications.
Co-reporter:Zhen Li;Dong-sheng Tan;Qi-lin Ren 傅强
Chinese Journal of Polymer Science 2013 Volume 31( Issue 2) pp:363-370
Publication Date(Web):2013 February
DOI:10.1007/s10118-013-1228-5
In this study, a UV-curable polysiloxane methacrylate (PSMA) was synthesized by a one-step method. The reaction was catalyzed by chloroplatinic acid between polymethylhydrosiloxane (PMHS) and hydroxyethyl methacrylate (HEMA), as proved by FTIR and 1H-NMR. The preliminary results indicate that the obtained UV-cured PSMA film has very good thermal stability, excellent transparency and satisfactory tensile strength. Our work provides a simple but efficient way to prepare UV-curable PSMA, which may find potential applications in UV-curing optical fiber, metal and glass coating and other fields.
Co-reporter:Li Yu-Han, Song-Gang Chai, Wei-Wei Yao, Sha Deng, Fu Qiang, Feng Chen
Materials Letters 2013 100() pp: 207-211
Publication Date(Web):
DOI:10.1016/j.matlet.2013.03.027
Co-reporter:Nanying Ning, Wei Zhang, Jiajie Yan, Fan Xu, Tiannan Wang, Hao Su, Changyu Tang, Qiang Fu
Polymer 2013 Volume 54(Issue 1) pp:303-309
Publication Date(Web):8 January 2013
DOI:10.1016/j.polymer.2012.11.045
Co-reporter:Chengzhen Geng, Juanjuan Su, Songjia Han, Ke Wang, Qiang Fu
Polymer 2013 Volume 54(Issue 13) pp:3392-3401
Publication Date(Web):7 June 2013
DOI:10.1016/j.polymer.2013.04.048
Controlling the hierarchical structure of melt-processed polymers is vital to “structuring” processing and tailoring properties of the product. In this work, polypropylene (PP)/octene-ethylene copolymer (POE) blends were injection-molded using so-called dynamic packing injection technique, which imposed oscillatory shear on the gradually cooled melt during the packing solidification stage. In this way, samples with highly oriented PP matrix and elongated POE particles were obtained. Most interestingly, it was found for the first time that the elongated POE particles could not improve any impact toughness of oriented PP, which is completely different from that for the isotropic ones. Polarized optical microscope, scanning electron microscope, micro-Fourier transform infrared spectroscopy and differential scanning calorimetry were used to characterize the microstructures along sample thickness. The crack-initiation term, impact fractured surface and cross-section of the impact surface were inspected to understand the difference in impact behavior between the oriented PP/POE blends and their isotropic counterparts. The results show that massive crazing or plastic flow of the matrix could not be effectively initiated in the oriented blends. Our work provides a good example for better understanding structure–property relationship of polymers via well controlling their internal hierarchical structure.
Co-reporter:Feilong Yu, Hua Deng, Qin Zhang, Ke Wang, Chaoliang Zhang, Feng Chen, Qiang Fu
Polymer 2013 Volume 54(Issue 23) pp:6425-6436
Publication Date(Web):1 November 2013
DOI:10.1016/j.polymer.2013.09.047
To prepare composites with anisotropic conductive networks, electrical conductive polymer composites (CPCs) consisting of polypropylene (PP) and carbon nanotubes (CNTs) filled polyethylene (PE) are fabricated through high speed thin-wall injection molding. Morphological study demonstrates that CNTs are localized in PE phase while the alternating multilayer structure with different polymer phases elongated as well as conductive network oriented parallel to flow direction is observed. To form such alternating layered structure, the dispersed phases are firstly deformed into discontinuous layers, and finally further deformed into wide and regular continuous alternating layers. In term of the mechanism behind this, the good viscosity match, low interfacial tension between different polymer components, short relaxation time and high shear rate are thought as important issues. The anisotropic conductive behavior of these CPCs, i.e. conductive in longitudinal (parallel to flow direction) and transverse (perpendicular to flow direction) direction but non-conductive in thickness direction, is contributed by the insulating PP layer which cuts off the conductive networks in the core layer. More importantly, much better electromagnetic interference (EMI) shielding ability is obtained for these CPCs with alternating multilayer conductive networks comparing with the same polymer blends with isotropic conductive networks, despite of the fact that much lower resistivity is obtained for the later. This indicates great potential of these anisotropic CPCs for electronic applications. Moreover, this study has shed some light on the potential use of such alternating multi-layered structure to prepare a range of multi-functional materials.
Co-reporter:Guanghui Yang, Juanjuan Su, Jian Gao, Xin Hu, Chengzhen Geng, Qiang Fu
The Journal of Supercritical Fluids 2013 Volume 73() pp:1-9
Publication Date(Web):January 2013
DOI:10.1016/j.supflu.2012.11.004
Poly(propylene carbonate) is a new amorphous, biodegradable and biocompatible aliphatic polyester. It has a potentially wide range of applications, such as packing materials and biomedical materials. However, the low glass transition temperatures (Tg) and poor mechanical property have limited its applications. In this paper, poly(propylene-carbonate)/graphene oxide nanocomposites with a 10 °C increase in Tg and a 50 times increase in storage modulus at 30 °C were firstly fabricated, then the nanocomposites were foamed using supercritical CO2 to widen their applications, particularly in the area of tissue engineering. It was demonstrated that the nanocomposite foams had good dimension stability and the final pore features were depended on supercritical CO2 saturation conditions. In addition, cytotoxicity and in vitro cell culturing tests of selected foams showed that the fabricated porous materials were non-cytotoxic and able to support cellular adhesion within the 3D structure, suggesting that these are promising materials for tissue engineering applications.Graphical abstractHighlights► PPC/GO nanocomposites were fabricated by a solution blending method. ► Well-controlled porous foams of PPC/GO were fabricated using supercritical CO2. ► The fabricated foams are promising materials in tissue engineering fields.
Co-reporter:Hongwei Bai, Chunmei Huang, Hao Xiu, Yao Gao, Qin Zhang, Qiang Fu
Polymer 2013 Volume 54(Issue 19) pp:5257-5266
Publication Date(Web):23 August 2013
DOI:10.1016/j.polymer.2013.07.051
Enhancing matrix crystallization has been demonstrated to be an effective method to simultaneously improve the impact toughness and heat resistance of poly(l-lactide) (PLLA) modified with flexible polymers, such as poly(ε-caprolactone) (PCL). Unfortunately, increasing PLLA matrix crystallinity alone cannot guarantee the enhancement of impact toughness in most cases, so other structural parameters should be considered. In this work, taking PLLA/PCL (80/20) blend as an example, the combined roles of matrix crystallization and impact modifier particle size in the toughening have been investigated. PLLA matrix crystallinity was controlled by adding a highly effective nucleating agent and PCL particle size was tailored by varying processing conditions while maintaining constant interfacial adhesion. It is interesting to find that toughening is efficient only if matrix crystallinity and particle size are well matched. With the significant increase of matrix crystallinity, an evident decrease of optimum particle size for toughening PLLA has been identified for the first time. Therefore, suitable particle size is the precondition for highly crystalline matrix to work effectively in the toughening because only small particles (0.3–0.5 μm) are effective in trigger shear yielding mechanism of the matrix needed for good toughness, whereas relatively large particles (0.7–1.1 μm) are only capable of toughening amorphous matrix effectively by initiating multiple crazing of the matrix. Importantly, our findings can be used to well explain the reason for the different roles of matrix crystallization in the toughening of different PLLA blends reported in the literature. Furthermore, the heat resistance of the blend with a highly crystalline matrix is much better than that of the blend with an amorphous one as expected. This work could not only provide a new insight into the synergistic roles of matrix crystallization and modifier particle size in the toughening of PLLA but also set up a universal framework for designing high-performance PLLA products with both good impact toughness and high heat resistance.
Co-reporter:Yashuo Xu, Xiangyang Wu, Xingyi Xie, Yinping Zhong, Robert Guidoin, Ze Zhang, Qiang Fu
Polymer 2013 Volume 54(Issue 20) pp:5363-5373
Publication Date(Web):6 September 2013
DOI:10.1016/j.polymer.2013.07.069
Traditional poly(ethylene glycol) (PEG)-modified polyurethanes usually exhibit high biocompatibility, but still lack reactivity with biological molecules to induce appropriate cell and tissue responses. In this study, PEG diglycidyl ether (Mn = 526 Da) and PEG bis(amine) (Mn = 1000 Da) were respectively grafted onto carboxyl-group-containing poly(carbonate urethane) backbones that chain-extended with lysine, to generate reactivity while maintaining biocompatibility. The PEG chains disordered and plasticized the hard segments where they attached, reducing H-bonded urea groups and lowering glass transition temperatures. The Mn ranged from 33,000 to 70,000 Da for the precursor polyurethanes, which largely decreased by 24–75% following PEG grafting. Hemocompatibility was enhanced due to the flexibility and hydrophilicity of the PEG chains. Solutions of the PEG-grafted polyurethanes were transformed into hydrocolloids when dropped into water. Reactivity was proved by immobilization of albumin onto the colloidal particles. These new functional PEG-grafted polyurethanes can potentially form multifunctional bioconjugates for applications as biomaterials and in pharmaceutics.
Co-reporter:Guanghui Yang, Xin Hu, Juanjuan Su, Chengzhen Geng, Weiwei Yao, Qin zhang, Qiang Fu
The Journal of Supercritical Fluids 2013 Volume 82() pp:200-205
Publication Date(Web):October 2013
DOI:10.1016/j.supflu.2013.08.003
•Biodegradable PPC/PMMA composites were prepared via a supercritical fluid route.•PMMA was dispersed on a nanometer scale (50–200 nm) in the PPC substrate.•The yield strength of PPC sharply increased 4 times by incorporating 5 wt% PMMA.•This study introduced an effective modification method of biodegradable PPC.Biodegradable poly(propylene carbonate) (PPC) matrix composite with a significant improvement in yield strength was successfully prepared by incorporating a low content of poly(methyl methacrylate) (PMMA) via a supercritical carbon dioxide route. Atomic force microscopy measurement shows that the size of the dispersed PMMA phase in the PPC substrate is in the range from 50 nm to 200 nm, which is much smaller than the smallest ones that can be obtained by conventional melt blending method. Tensile tests demonstrate the excellent mechanical properties of the composites prepared in this study. By incorporating only 5 wt% PMMA, the obtained composites show approximately 4 times higher yield strength than pure PPC and the elongation at break of the composites is well remained. By comparing with the reported works, this method shows the highest enhancement efficiency of PPC. The significant reinforcement of PPC is ascribed to the nano size phase-separated domains of rigid PMMA. These findings show an effective modification method of PPC for the potential alternative to the non-biodegradable polymers.
Co-reporter:Nanying Ning, Sirui Fu, Wei Zhang, Feng Chen, Ke Wang, Hua Deng, Qin Zhang, Qiang Fu
Progress in Polymer Science 2012 Volume 37(Issue 10) pp:1425-1455
Publication Date(Web):October 2012
DOI:10.1016/j.progpolymsci.2011.12.005
Polymer/filler composites have been widely used in various areas. One of the keys to achieve the high performance of these composites is good interfacial interaction between polymer matrix and filler. As a relatively new approach, the possibility to enhance polymer/filler interfacial interaction via crystallization of polymer on the surface of fillers, i.e., interfacial crystallization, is summarized and discussed in this paper. Interfacial crystallization has attracted tremendous interest in the past several decades, and some unique hybrid crystalline structures have been observed, including hybrid shish–kebab and hybrid shish–calabash structures in which the filler served as the shish and crystalline polymer as the kebab/calabash. Thus, the manipulation of the interfacial crystallization architecture offers a potential highly effective route to achieve strong polymer/filler interaction. This review is based on the latest development of interfacial crystallization in polymer/filler composites and will be organized as follows. The structural/morphological features of various interfacial crystallization fashions are described first. Subsequently, various influences on the final structure/morphology of hybrid crystallization and the nucleation and/or growth mechanisms of crystallization behaviors at polymer/filler interface are reviewed. Then recent studies on interfacial crystallization induced interfacial enhancement ascertained by different research methodologies are addressed, including a comparative analysis to highlight the positive role of interfacial crystallization on the resultant mechanical reinforcement. Finally, a conclusion, including future perspectives, is presented.
Co-reporter:Li Chen, Songgang Chai, Kai Liu, Nanying Ning, Jian Gao, Qianfa Liu, Feng Chen, and Qiang Fu
ACS Applied Materials & Interfaces 2012 Volume 4(Issue 8) pp:4398
Publication Date(Web):August 2, 2012
DOI:10.1021/am3010576
Controlling the interface interaction of polymer/filler is essential for the fabrication of high-performance polymer composites. In this work, a core–shell structured hybrid (SiO2–GO) was prepared and introduced into an epoxy polymer matrix as a new filler. The incorporation of the hybrid optimized the modulus, strength and fracture toughness of the composites simultaneously. The ultrathin GO shells coated on silica surfaces were regarded as the main reason for the enhancement. Located at the silica-epoxy interface, GO served as an unconventional coupling agent of the silica filler, which effectively enhanced the interfacial interaction of the epoxy/SiO2–GO composites, and thus greatly improved the mechanical properties of the epoxy resin. We believe this new and effective approach that using GO as a novel fillers surface modifier may open a novel interface design strategy for developing high performance composites.Keywords: core−shell structure; epoxy; graphene oxide; interfacial enhancement;
Co-reporter:Hongwei Bai, Hao Xiu, Jian Gao, Hua Deng, Qin Zhang, Mingbo Yang, and Qiang Fu
ACS Applied Materials & Interfaces 2012 Volume 4(Issue 2) pp:897
Publication Date(Web):January 3, 2012
DOI:10.1021/am201564f
Melt blending poly(l-lactide) (PLLA) with various biodegradable polymers has been thought to be the most economic and effective route to toughen PLLA without compromising its biodegradability. Unfortunately, only very limited improvement in notched impact toughness can be achieved, although most of these blends show significant enhancement in tensile toughness. In this work, biodegradable poly(ε-caprolactone) (PCL) was used as an impact modifier to toughen PLLA and a nucleating agent was utilized to tailor the crystallization of PLLA matrix. Depending on the nucleating agent concentrations in the matrix and mold temperatures in injection molding, PLLA/PCL blends with a wide range of matrix crystallinity (10–50%) were prepared by practical injection molding. The results show that there is a linear relationship between PLLA matrix crystallinity and impact toughness. With the increase in PLLA crystalline content, toughening becomes much easier to achieve. PLLA crystals are believed to provide a path for the propagation of shear yielding needed for effective impact energy absorption, and then, excellent toughening effect can be obtained when these crystals percolate through the whole matrix. This investigation provides not only a new route to prepare sustainable PLLA products with good impact toughness but also a fresh insight into the importance of matrix crystallization in the toughening of semicrystalline polymers with a flexible polymer.Keywords: biodegradable polymer; crystallization; poly(l-lactide); renewable resource; sustainable materials; toughness;
Co-reporter:Dongsheng Tan;Xiaoqing Zhang;Jiehua Li;Hong Tan
Journal of Biomedical Materials Research Part A 2012 Volume 100A( Issue 2) pp:380-387
Publication Date(Web):
DOI:10.1002/jbm.a.33191
Abstract
In order to improve the blood compatibility, poly(ether urethane) (PEU) and fluorinated phosphorylcholine polyurethane (P-HFPC) were used to prepare PU/P-HFPC blends by solution mixing. The hemocompatibility in vitro was evaluated with protein adsorption and platelet-rich plasma (PRP) contact tests. It was found that the amount of adsorbed protein on surface was decreased by 87%, and almost no platelet adhesion and activation was observed on the surface of blends when P-HFPC content was above 5 wt %. After adding P-HFPC, the blends basically kept favorable mechanical properties of PEU though the content of P-HFPC rises to 20 wt %. To better understand the relationship between structure and properties, the phase structure and surface property of the blend films were further investigated via differential scanning calorimetry, dynamic mechanical analysis, atomic force microscopy, X-ray photoelectron spectroscopy, and contact angle measurements. The results indicated that the fluorinated phosphorylcholine units could be easily enriched on the surface of blend films due to the phase separation between the PEU and P-HFPC. Therefore, ordinary poly(ether urethane)s can obtain both satisfactory blood compatibility and good mechanical properties just by blending with small amount of P-HFPC. © 2011 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2012.
Co-reporter:Dongsheng Tan, Xiaoqing Zhang, Jiehua Li, Hong Tan, Qiang Fu
Applied Surface Science 2012 Volume 258(Issue 7) pp:2697-2706
Publication Date(Web):15 January 2012
DOI:10.1016/j.apsusc.2011.10.120
Abstract
A novel phospholipid containing double chains and phosphotidylcholine polar head groups, 2-(10-(2-aminoethylamino)-10-oxodecanamido)-3-(decyloxy)-3-oxopropyl phosphorylcholine (ADDPC), was synthesized and characterized. Two kinds of double-chain phospholipid end-capped polyurethanes with different soft segments were prepared. The structure of prepared polyurethanes was characterized by X-ray photoelectron spectroscopic (XPS), attenuated total reflection Fourier transform infrared (ATR-FTIR) spectrometry and atomic force microscope (AFM), which indicated that the double-chain phospholipids enriched onto the top surface of the prepared polyurethane films. The preliminary evaluation of blood compatibility showed that these novel phospholipid end-capped polyurethanes could suppress platelet adhesion and activation effectively. This property did not depend on the chemical structure of polyurethanes. In addition, according to tensile test results, the phospholipid polyurethanes kept good mechanical properties in comparison with original polyurethanes. It is suggested that double-chain phospholipid end-caption has good potential for achieving both hemocompatibility and good mechanical properties simultaneously for polyurethanes.
Co-reporter:Zhoukun He, Meng Ma, Xiangchuan Xu, Jianying Wang, Feng Chen, Hua Deng, Ke Wang, Qin Zhang, Qiang Fu
Applied Surface Science 2012 Volume 258(Issue 7) pp:2544-2550
Publication Date(Web):15 January 2012
DOI:10.1016/j.apsusc.2011.10.090
Abstract
Herein, we report a facile and low cost method for the fabrication of superhydrophobic surface via spin coating the mixture of polydimethylsiloxane precursor (PDMS) and silicon dioxide (SiO2) nanoparticles. The surface hydrophobicity can be well tuned by adjusting the weight percent of PDMS and SiO2. The water contact angle (WCA) can increase from 106.8 ± 1.2° on PDMS film to 165.2 ± 2.3° on PDMS/SiO2 coating, companying with a change from adhering to rolling which was observed from tilting angle (TA) characterization. Multi-scale physical structures with SiO2 nanoparticle aggregates and networks of SiO2 nanoparticle aggregates are characterized by scanning electron microscopy (SEM) and atomic force microscope (AFM), and they can be observed more clearly from the AFM images treated with software (WSxM). Then the relationship between surface hydrophobicity and structures is further discussed based on Wenzel and Cassie models, indicating that the appearance of networks of nanoparticle aggregates is important in the Cassie state. The superhydrophobic coating can keep the superhydrophobicity at least for one month under environment conditions and readily regenerate after mechanical damage. Additionally, the superhydrophobic coating can be fabricated using other methods including dip coating, spray coating and casting. Thus, a large area of superhydrophobic coatings can be easily fabricated. Therefore the range of possible applications for these facile and versatile methods can be expanded to various actual conditions.
Co-reporter:Nanying Ning;Hua Deng;Feng Luo;Qin Zhang;Ke Wang;Feng Chen
Polymers for Advanced Technologies 2012 Volume 23( Issue 3) pp:431-440
Publication Date(Web):
DOI:10.1002/pat.1894
Abstract
Interfacial interaction plays a key role in the preparation of high performance polymer composites. In this work, in order to explore the possibility to enhance the interfacial interaction via interfacial crystallization of polymer matrix onto the filler surface, interfacial crystallization structure and mechanical properties of linear low density polyethylene (LLDPE)/whisker composites were investigated. The composites were firstly prepared by melt compounding, followed by processing in both traditional and dynamic injection molding. DSC, WAXD, SEM were used to characterize the interfacial crystallization structure. And the mechanical properties were measured by tensile testing. An imperfect shish-calabash structure, with whisker served as shish, and irregular LLDPE spherulite as imperfect calabash, was formed during common injection molding processing. Such a structure was considered as the main reason for the strong interfacial adhesion and the obviously improved tensile strength and modulus. Furthermore, introducing shear could cause the formation of relatively perfect shish-calabash structure, leading to the stronger interfacial adhesion. Copyright © 2011 John Wiley & Sons, Ltd.
Co-reporter:Nanying Ning;Wei Zhang;Yongsheng Zhao;Feng Luo
Polymer International 2012 Volume 61( Issue 11) pp:
Publication Date(Web):
DOI:10.1002/pi.4252
Abstract
In our previous work, the formation of a nanohybrid shish kebab (NHSK) structure was successfully achieved in helical polymer systems promoted by using single-walled carbon nanotube (CNT) bundles with a unique ‘groove structure’, which is of great crystallographic interest. To further investigate the effect of surface groove structure of CNT bundles on the formation of NHSK structure in helical polymer systems, in the work reported here double-walled carbon nanotube (DWNT) fibers with bundle structure were used as nucleating agents and orientation templates for poly(L-lactide) (PLLA) crystallization. A fine NHSK structure with controlled lateral size and period of kebabs was successfully obtained under various experimental conditions by using DWNT bundles. This could be due to the geometric confinement effect of the surface groove structure of the DWNT bundles, which could facilitate the orientation of PLLA chains along the DWNT axis and the lateral formation of a stable nucleus. Our work suggests an efficient method for the functionalization of CNTs with biocompatible PLLA, which may have some potential applications in biomedical areas. In addition, it is demonstrated that the formation of NHSK structure can effectively improve the physical bonding between PLLA and nanotubes, thus significantly improving the mechanical properties of PLLA/CNT nanocomposite fibers. Copyright © 2012 Society of Chemical Industry
Co-reporter:Dong Liang;Li-juan Zhou;Qin Zhang 张琴;Feng Chen
Chinese Journal of Polymer Science 2012 Volume 30( Issue 4) pp:603-612
Publication Date(Web):2012 July
DOI:10.1007/s10118-012-1159-6
The morphology and mechanical properties of poly(ethylene-octene) copolymers (POE) obtained by dynamic packing injection molding were investigated by mechanical tests, differential scanning calorimetry (DSC), fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The mechanical tests found that only POE with low octene content and high molecular weight show apparent response for external shear field. Further investigation has been done by DSC, FT-IR, and SEM in order to make clear the reason of that phenomenon. Finally, the hypothetical mechanism of POE microstructure formation under shear field has been proposed. For POE with low octene content and high molecular weight, orientation degree and mechanical properties both increase substantially under shear field. For POE with low octene content and low molecular weight, orientation degree and crystallinity increase under shear field, but it is not dramatically benefit for the mechanical properties. For POE with high octene content and high molecular weight, the shear field has little effect on the morphology and mechanical properties.
Co-reporter:Shuangmei Zhang;Lin Lin;Hua Deng;Xiang Gao
Colloid and Polymer Science 2012 Volume 290( Issue 14) pp:1393-1401
Publication Date(Web):2012 September
DOI:10.1007/s00396-012-2661-7
Dynamic percolation in highly oriented conductive networks formed with different carbon nanofillers is investigated during disorientation upon annealing. Conductive networks are constructed by solid-state drawing, subsequent annealing, and using fillers with different dimensions (multiwalled carbon nanotubes (MWCNTs) and carbon black (CB)) in a bicomponent tape. Interestingly, it is observed that a less entangled network work is formed by mixed filler containing CB; consequently, this result in an accelerated dynamic percolation process and reduced activation energy of such process. Three different analytical approaches have been utilized to analyze this interesting behavior. It is concluded that the dynamic percolation process in highly oriented conductive polymer composites filled with MWCNTs can indeed be accelerated by the addition of CB, since less entangled networks are formed in a hybrid filler system compared with MWCNTs alone.
Co-reporter:Jian Gao, Qin Zhang, Ke Wang, Qiang Fu, Yong Chen, Hongyu Chen, Hua Huang, Jose M. Rego
Composites Part A: Applied Science and Manufacturing 2012 Volume 43(Issue 4) pp:562-569
Publication Date(Web):April 2012
DOI:10.1016/j.compositesa.2011.12.030
High density polyethylene (HDPE)/attapulgite (AT) nanocomposites, prepared by conventional injection molding (CIM) and dynamic packing injection molding (DPIM), were investigated with focus on AT-induced crystallization and orientation under shear. Infrared spectroscopy (FTIR) analysis showed there is no special chemical interaction between HDPE and AT, but shear induced significant changes on the material structure and properties. Differential scanning calorimetry (DSC) analysis showed strong nucleation effect by AT especially under shear. And more, shear will induce much better dispersion of AT in the DPIM sample vs. CIM. AT nanorods and lamellae of HDPE are more organized in the DPIM sample while there is only random distribution in the CIM sample. Most AT nanorods embed in the HDPE lamellae and form a brush-like hybrid structure due to shear. The shear-induced orientation will be enhanced with higher AT loading. The mechanical performance of the composites was significantly improved via DPIM.
Co-reporter:Meng Ma, Feng Chen, Ke Wang, Qin Zhang, Hua Deng, Zhongming Li, and Qiang Fu
Macromolecules 2012 Volume 45(Issue 11) pp:4932-4937
Publication Date(Web):May 14, 2012
DOI:10.1021/ma3000779
Co-reporter:Lijuan Zhou, Dong Liang, Xueling He, Jiehua Li, Hong Tan, Jianshu Li, Qiang Fu, Qun Gu
Biomaterials 2012 33(9) pp: 2734-2745
Publication Date(Web):
DOI:10.1016/j.biomaterials.2011.11.009
Co-reporter:Jianchuan Wang, Qiang Fu, Qin Zhang
Polymer 2012 Volume 53(Issue 24) pp:5455-5458
Publication Date(Web):9 November 2012
DOI:10.1016/j.polymer.2012.09.057
Polar β and γ crystalline forms, especially the β form, are of great importance to the piezoelectric/ferroelectric property of poly(vinylidene fluoride) (PVDF). Dominant polar crystal forms (containing both β and γ forms) are induced in PVDF by simply adding a small amount of dioctadecyl dimethyl ammonium chloride (DDAC, a kind of alkyl ammonium salt used to treat clay). By comparing with the PVDF/clay and PVDF/DDAC modified-clay systems, it is demonstrated that it is DDAC that induces polar β and γ forms of PVDF rather than organoclay itself. The widely accepted mechanism that crystal lattice matching between PVDF and clay induces β form in PVDF/organoclay composite might be wrong. It is also interesting to find that super tensile toughness can be achieved by adding a small amount of DDAC. These new findings are very important for the understanding of the formation mechanism of polar forms of PVDF and its application.
Co-reporter:Feng Luo, Yanling Zhu, Ke Wang, Hua Deng, Feng Chen, Qin Zhang, Qiang Fu
Polymer 2012 Volume 53(Issue 21) pp:4861-4870
Publication Date(Web):28 September 2012
DOI:10.1016/j.polymer.2012.08.037
Polypropylene random copolymer (PPR) is one of important polypropylene types for the application fields needing for excellent toughness. Because of the random copolymer chain configuration, the polymorphic behavior of PPR is difficult to be altered even by adding β-nucleating agent (β-NA). In this study, a promising method was developed by adding isotactic polypropylene (iPP) into PPR/β-NA blend, which has leaded to a surprising enhancement in the β-crystallization capability of PPR. At the optimal component condition, the β-crystal content of PPR can reach the highest level of 92 % and the β-crystallization capability is improved by 56%. As a result of high β-crystal contents, a superior mechanical toughness has been attained. On the other hand, the fractional crystallization experiment suggests that the stereoregular chains of iPP could assist the formation of primary β-nuclei at the very early stage of crystallization. This special crystallization event dominates the final polymorphic composition in PPR. Furthermore, it is demonstrated that impact polypropylene copolymer (IPC) can be used to substitute iPP for the improvement of β-crystal content of PPR. This provides a huge possibility to improve the low temperature properties of PPR to enlarge its applications.Graphical abstract
Co-reporter:Yongsheng Zhao, Nanying Ning, Xin Hu, Yuhan Li, Feng Chen, Qiang Fu
Polymer 2012 Volume 53(Issue 19) pp:4310-4317
Publication Date(Web):31 August 2012
DOI:10.1016/j.polymer.2012.07.016
The mechanical responses including monotonic and cyclic tensile responses have been investigated on a microphase-separated poly (styrene-isoprene-styrene) triblock copolymer (SIS). The specimens were injection-molded by using different melt temperatures to acquire different microphase structures. As a result of temperature-dependent segregation driving force, the specimens with reduced microphase separation can be obtained by increasing processing melt temperature from 180 °C to 240 °C. On the basis of stress-strain behavior, Young's modulus was found to increase with increasing PS domain continuity in the order of disorder state to disordered spheres to body-cubic-centered (BCC) spheres to oriented cylinders morphology. Meanwhile, cyclic hysteresis decreases with reduced microphase separation and with decreasing the applied predetermined maximum tensile strain. In addition, the Mooney–Rivlin phenomenological approach was used to evaluate and explore the relationship between the polymer topological networks and the rubber elasticity of thermoplastic elastomers.Graphical abstract
Co-reporter:Nanying Ning, Wei Zhang, Yongsheng Zhao, Changyu Tang, Mingbo Yang, Qiang Fu
Polymer 2012 Volume 53(Issue 20) pp:4553-4559
Publication Date(Web):12 September 2012
DOI:10.1016/j.polymer.2012.07.060
Periodic patterning of carbon nanotubes (CNTs) with semi-crystalline polymers, especially the novel nanohybrid shish kebab (NHSK) superstructure, in which fibrous CNTs act as shish while polymer lamellae as kebab, is of interest both scientifically and technologically. So far the reported NHSK are mostly prepared using polymers with zigzag conformation in crystal and it seems difficult to obtain NHSK using polymer with helical conformation. In this work, we report the formation of NHSK structure by using single-walled carbon nanotube (SWNT) bundles. A promoted formation of NHSK was observed even using polymer with helical conformation, and the formation mechanism of NHSK was attributed to the unique “groove structure” formed by the stacked SWNTs in parallel arrays, which could facilitate the orientation of helical polymer chains along the SWNTs axis and the lateral formation of stable nucleus. The NHSK structure in helical polymer/SWNT bundles system could widen application of this unique superstructure, offering value in both application field and crystallography aspect as well.
Co-reporter:Feng Luo, Chenlong Xu, Ke Wang, Hua Deng, Feng Chen, Qiang Fu
Polymer 2012 Volume 53(Issue 8) pp:1783-1790
Publication Date(Web):3 April 2012
DOI:10.1016/j.polymer.2012.02.024
In this study, the effects of α- and β-nucleating agents (α-NA and β-NA) on the toughening behavior of impact polypropylene copolymer were ascertained with respect to three test temperatures (23, 0 and −15 °C). The addition of α-NA impacted the toughness slightly for all test temperatures. However, the tendency of impact strength vs. β-NA content at 0 °C significantly differs from that of the other two temperatures. Importantly, a close correlation between toughness at 0 °C and chain mobility of the amorphous portion has been well revealed for the first time by achieving a linearly fitting between impact strength at 0 °C and β-relaxation peak intensity in DMA spectrum. A comparative investigation between the situations containing α-NA or β-NA offers new insights into the physical origin of the toughening behavior for a multiphase multicomponent polyolefin system. The chain mobility of matrix amorphous portion plays a dominant role on toughening.
Co-reporter:Yao Gao, Kun Ren, Nanying Ning, Qiang Fu, Ke Wang, Qin Zhang
Polymer 2012 Volume 53(Issue 13) pp:2792-2801
Publication Date(Web):7 June 2012
DOI:10.1016/j.polymer.2012.04.020
Crystalline structures especially the interfacial crystalline layers of semi-crystalline polymer/filler composites are markedly affected by the extensional force and keep an important role in macroscopic properties. In this study, we prepared the polypropylene and SiO2–MgO–CaO whisker (SMCW) composite fibers by melt-spun technology. The structure–property relationship of the PP/SMCW composite fibers was investigated by scanning electron microscopy, polarizing light microscopy, differential scanning calorimeter, the polarized Fourier transform infrared spectroscopy and tensile test. Two different interfacial crystalline structures were observed by adopting two drawn ratios – shish-calabash structure obtained at the low drawn ratio and transcrystalline (TC) structure obtained at the high drawn ratio. Remarkable reinforcement of the fibers was realized for the composite fibers prepared at high drawn ratio, compared with that obtained at the low drawn ratio. It was deduced that the formation of transcrystalline structure could result in a better interfacial interaction than shish-calabash structure, and could be one of the most important reasons for the large improvement of tensile properties of composite fibers fabricated at high drawn ratio.
Co-reporter:Jian Gao, Feng Chen, Ke Wang, Hua Deng, Qin Zhang, Hongwei Bai and Qiang Fu
Journal of Materials Chemistry A 2011 vol. 21(Issue 44) pp:17627-17630
Publication Date(Web):17 Oct 2011
DOI:10.1039/C1JM14300J
We show an order of magnitude increase in yield strength and Young's modulus of poly(propylene carbonate) (PPC) by adding a small amount of graphene oxide (GO) nanosheets, accompanied by a dramatic increase of glass transition temperature (Tg). The reinforced tensile properties are comparable to those of conventional polyethylene. This work opens the door to replace conventional polyethylene by PPC.
Co-reporter:Kai Liu, Li Chen, Yao Chen, Jieli Wu, Weiyi Zhang, Feng Chen and Qiang Fu
Journal of Materials Chemistry A 2011 vol. 21(Issue 24) pp:8612-8617
Publication Date(Web):11 May 2011
DOI:10.1039/C1JM10717H
The introduction of graphene into a polymer matrix can markedly improve its mechanical properties and electrical conductivity. We report herein a novel strategy to fabricate polyester/reduced graphene oxide composites via simultaneous dispersion and thermo-reduction of graphene oxide (GO) during in situ melt polycondensation. The pristine graphite was first oxidized using a strong oxidant acid to prepare GO, and then GO sheets were dispersed into ethylene glycol (EG), where a homogeneous dispersion of GO in EG was obtained with ultrasonication. Finally polyester/reduced graphene oxide composites were prepared via in situpolymerization of terephthalic acid (PTA) and ethylene glycol containing well dispersed GO. Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and sedimentation experiments have been used to characterize the prepared composites. It is demonstrated that poly(ethylene terephthalate) (PET) chains may have been sucessfully grafted onto GO sheets during polymerization, accompanied by the thermo-reduction from GO to graphene. The TGA and XPS results showed that the content of grafted PET polymer was about to 60–80%, which indicates a homogeneous dispersion of GO sheets in the PET matrix, as demonstrated by SEM. Furthermore, a significant improvement in tensile strength and elongation at break of PET has been achieved. Therefore, our work provides a new way for the preparation of polyester/reduced graphene oxide composites and functionalization of graphene.
Co-reporter:Mingming Ding, Zongzheng Qian, Jin Wang, Jiehua Li, Hong Tan, Qun Gu and Qiang Fu
Polymer Chemistry 2011 vol. 2(Issue 4) pp:885-891
Publication Date(Web):20 Jan 2011
DOI:10.1039/C0PY00376J
We have recently developed a new group of cationic biodegradable multiblock poly(ε-caprolactone urethane)s bearing gemini quaternary ammonium pendant groups and methoxyl-poly(ethylene glycol) (m-PEG) end chains. In this study, to endow polyurethane with attractive amphiphilicity and good biocompatibility, and to achieve a fundamental understanding on the structure-property relationship of these polyurethanes in favor of designing and preparing new generation of polyurethanes with more attractive amphiphilicity and better biocompatibility, varying amounts of m-PEG were introduced into the polyurethane chains and the effect of PEG content on the polymer bulk properties was investigated in detail by using Fourier transform infrared (FTIR) spectra, differential scanning calorimetry (DSC), water contact angle (WCA) measurements, polarizing light microscopy (PLM) and in vitrodegradation studies. It was found that the incorporation of PEG has direct effects on the phase behaviors, thermal properties, hydrophilicity and degradable ability of poly(ε-caprolactone urethane)s. Moreover, these polyurethanes exhibit good cytocompatibility, which are promising biodegradable carrier materials in drug delivery and interesting candidates for further study.
Co-reporter:Zhigao Wang, Lunquan Yu, Mingming Ding, Hong Tan, Jiehua Li and Qiang Fu
Polymer Chemistry 2011 vol. 2(Issue 3) pp:601-607
Publication Date(Web):04 Nov 2010
DOI:10.1039/C0PY00235F
To obtain rapid biodegradable biomaterials, a biodegradable triblock oligomer poly(lactic acid)-poly(ethylene glycol)-poly(lactic acid) (PLA-PEG-PLA) was designed and synthesized as a soft segment of polyurethane. Then new nontoxic biodegradable polyurethanes were prepared using the same stoichiometric ratio of PLA-PEG-PLA, L-lysine ethyl ester diisocyanate (LDI), and 1,4-butanediol (BDO). The molecular weights of polyurethanes were controlled by adjusting the polymerization temperature. The resulting polyurethanes were characterized by gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC). Furthermore, the biodegradability of the synthesized polyurethanes was evaluated at 37 °C in phosphate buffer solutions (PBS) under different pH values and enzymatic solution at pH 7.4. The results showed that these polyurethanes could be rapidly degraded in PBS and enzymatic solution, as demonstrated by weight loss measurements and scanning electron microscope (SEM) observations. The degradation rates of these polyurethanes were mainly regulated by microphase separation degree, and could be restrained in lower pH value PBS. Moreover, the degradation products did not significantly decrease the pH value of incubation media, which would be useful to improve biocompatibilities of these polyurethanes in vivo. The current work provides a more promising approach to prepare nontoxic biodegradable polyurethanes with rapid degradation rates. These new materials may find potential use for drug delivery systems and magnetic resonance imaging (MRI) contrast agents.
Co-reporter:Zhoukun He, Meng Ma, Xiaorong Lan, Feng Chen, Ke Wang, Hua Deng, Qin Zhang and Qiang Fu
Soft Matter 2011 vol. 7(Issue 14) pp:6435-6443
Publication Date(Web):01 Jun 2011
DOI:10.1039/C1SM05574G
We herein provide an effective method to fabricate a transparent superamphiphobic coating with superhydrophobicity and near-superoleophobicity, the finished coating also shows improved stability under various measurements. To do this, a transparent superhydrophobic coating was first prepared with polydimethylsiloxane (PDMS) and hydrophobic silicon dioxide (SiO2) nanoparticles. Then the coating was sintered to degrade the PDMS into SiO2 before it was further oxidized into silanol (Si–OH). Finally, the coating was treated with 1H, 1H, 2H, 2H-Perfluorooctyl-trichlorosilane (PFTS). The PFTS treated coating shows transparency, superhydrophobicity with a water contact angle of 152.7 ± 2.1° and near-superoleophobicity with a diiodomethane contact angle of 140.7 ± 3.2°. The droplets of water and diiodomethane can simultaneously slide off the surface with a sliding angle of less than 6°. Moreover, the PFTS treated coating shows a higher stability than the PDMS/SiO2 coating fabricated by spin coating under various environmental conditions. The PFTS treated coating also shows quite good stability under high temperature environment. The superamphiphobic properties, transparency and improved stability of the PFTS treated coating are systemically discussed and the results show that the finished coating may be appropriate for many outdoor applications.
Co-reporter:Jinghui Yang, Qi Wang, Weiwei Yao, Feng Chen, Qiang Fu
Applied Surface Science 2011 Volume 257(Issue 11) pp:4928-4934
Publication Date(Web):15 March 2011
DOI:10.1016/j.apsusc.2010.12.151
Abstract
Self assembly of poly(styrene-b-dimethylsiloxane) (PS-b-PDMS) followed by reactive ion etching technique is a promising method for fabricating periodical silica nanopatterns and can be applicable for device fabrication on nanoscale. We demonstrated a technologically useful way to control the inorganic silica nanostructures in thin films by directly mixing asymmetric (PS-b-PDMS) diblock copolymer with homopolymers of majority component, polystyrene (PS) under solvent vapor annealing followed by UV/O3 treatment. The effects of molecular weight and volume fraction of added homopolymer (PS) on morphology and size of the nanostructure of blends have been carefully investigated by atomic force microscopy. Different morphology transitions observed on the ordering film surface by atomic force microscopy (AFM) are associated with kinetics of phase evolution with respect to homo-PS with different molecular weight. The periodic spacings and dimensions of the microdomains were readily tuned at the same time, just by adjusting the molecular weight and volume fraction of the blended homopolymer.
Co-reporter:Run Su;Ke Wang;Qin Zhang;Feng Chen;Nan Hu;Erqiang Chen
Polymers for Advanced Technologies 2011 Volume 22( Issue 2) pp:225-231
Publication Date(Web):
DOI:10.1002/pat.1522
Abstract
In this work, as a part of a long-term project aimed at controlling of crystal structure and phase morphology for a injection molded product, we investigated the oriented structure and possible epitaxial growth of polyolefin blend (low-density polyethylene (LLDPE)/isotatic polypropylene (iPP)), achieved by dynamic packing injection molding, which introduced strong oscillatory shear on the gradually-cooled melt during the packing process. The crystalline and oriented structures of the prepared blends with different compositions were estimated in detail through 2D X-ray diffraction, calorimetry, and optical microscopy. As iPP was the dominant phase (its content was more than 50 wt%), our results indicated that it could be highly oriented in the blends. In such case, it was interesting to find that LLDPE epitaxially crystallized on the oriented iPP through a crystallographic matching between (100)LLDPE and (010)iPP, resulting in an inclination of LLDPE chains, about 50° to the iPP chain axis. On the other hand, as iPP was the minor phase, iPP was less oriented and no epitaxial growth between iPP and LLDPE was observed; even LLDPE remained oriented. The composition-dependent epitaxial growth of LLDPE on oriented iPP could be understood as due to: (1) the effect of crystallization sequence, it was found that iPP always crystallized before LLDPE for all compositions; (2) the dependence of oriented iPP structure on the blend composition; (3) the “mutual nucleation” between LLDPE and iPP due to their partial miscibility. Copyright © 2009 John Wiley & Sons, Ltd.
Co-reporter:Hong Yang;Bo Li;Qin Zhang;Rongni Du
Polymers for Advanced Technologies 2011 Volume 22( Issue 6) pp:857-862
Publication Date(Web):
DOI:10.1002/pat.1588
Abstract
The electrical conductivity and impact strength of polypropylene(PP)/EPDM/carbon black ternary composites were investigated in this paper. Two processing methods were employed to prepare these ternary composites. One was called one-step processing method, in which the elastomer and the filler directly melt blended with PP matrix. Another one was called two-step processing method, in which the elastomer and the filler were mixed first, and then melt blended with pure PP. To get an optimal phase morphology that favors the electrical conductivity and impact strength, controlling the distribution of CB in PP/EPDM blend was a crucial factor. Thus the interfacial tension and the work of adhesion were first calculated based on the measurement of contact angle, and the results showed that CB tended to be accumulated around EPDM phases to form filler-network structure. Expectably, the filler-network structure was observed in PP/EPDM/CB(80/20/3) composite prepared by two-step processing method. The formation of this filler-network structure decreased the percolation threshold of CB particles in polymer matrix, and the electrical conductivity as well as Izod impact strength of the composite increased dramatically. This work provided a new way to prepare polymer composites with both improved conductivity and impact strength. Copyright © 2009 John Wiley & Sons, Ltd.
Co-reporter:Tian-nan Zhou;Zai-chuan Hou;Ke Wang;Qin Zhang
Polymers for Advanced Technologies 2011 Volume 22( Issue 9) pp:1359-1365
Publication Date(Web):
DOI:10.1002/pat.1626
Melt mixing with a polymer is a novel strategy to modify the surface property of carbon nanotube (CNT) conveniently and efficiently. In melt mixing process, the shearing and thermal issues can make polymer component wrapped around nanotubes via π–π stacking interaction. In this study, polystyrene-coated multi-walled carbon nanotubes (MWNTs) was achieved through simple melt mixing of polystyrene with MWNTs. PS and MWNTs were first melt mixed at various melt time and temperatures to find the optimum condition for preparing of PS-coated MWNTs. Subsequently, the stability of polystyrene interacted with MWNTs was estimated via ultrasonication and thermal gravimetric analysis (TGA). Finally, the physically modified MWNTs were used to enhance polystyrene. An obvious mechanical reinforcement can be achieved, which approves a huge potential of application of these modified MWNTs in practical composite products. Copyright © 2009 John Wiley & Sons, Ltd.
Co-reporter:Feng Luo;Ke Wang;Jinwen Wang;Hua Deng;Qin Zhang;Feng Chen;Bing Na
Polymer International 2011 Volume 60( Issue 12) pp:1705-1714
Publication Date(Web):
DOI:10.1002/pi.3135
Abstract
In this study, a facile route to realize the superior toughness of injection molded polypropylene random copolymer (PPR) is reported. The toughness of PPR is increased about twofold when the processing melt temperature increases from 180 to 250 °C. Systematic and detailed structural characterizations have been carried out to establish the structure–property relationships by using polarized light microscopy, scanning electron microscopy, infrared microscopy and dynamic mechanical analysis. It is found that increasing the melt temperature is beneficial for the coalescence of rubbery domains and enhanced molecular mobility which are mainly responsible for the improvement in toughness. Other factors, such as molecular orientation, crystallinity and so on, seem to have little effect. The vital role of enhanced molecular mobility in improving toughness is further demonstrated by the annealing of injection molded samples at elevated temperature, i.e. 110 °C. Copyright © 2011 Society of Chemical Industry
Co-reporter:Nan Li;Ping Luo;Kai Liu;Li Chen;Ke Wang;Feng Chen
Journal of Applied Polymer Science 2011 Volume 121( Issue 1) pp:604-611
Publication Date(Web):
DOI:10.1002/app.33729
Abstract
To improve the crystallization and mechanical properties of poly(ethylene terephthalate) (PET), in this work, PET/SiO2-MgO-CaO whiskers composites were prepared via in situ polymerization. The morphology, crystallization, and mechanical properties of the prepared composites were investigated. It was found that inorganic whiskers could be easily dispersed in PET matrix, as demonstrated by SEM and PLM. DSC and PLM observation indicated a strong nucleation capability of inorganic whiskers for PET. Mechanical analysis results showed that the glass transition temperature, tensile strength, and modulus of the composites were greatly improved. A possible chemical bonding between PET chains and the surface of whiskers was observed by FTIR, TGA, and sedimentation experiment. It could be the main reason for the good dispersion and improved properties of the prepared composites. This work is important for the application of PET due to the low cost but high reinforcing efficiency of this inorganic whisker. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Co-reporter:Feng Luo;Ke Wang;Nanying Ning;Chengzhen Geng;Hua Deng;Feng Chen;Yuying Qian;De Zheng
Polymers for Advanced Technologies 2011 Volume 22( Issue 12) pp:2044-2054
Publication Date(Web):
DOI:10.1002/pat.1718
Abstract
As part of a continuous effort to develop high performance isotactic polypropylene (iPP) based on β-form crystalline and morphological change induced by rare earth nucleator (WBG), various WBG contents (from 0.025 to 1.0 wt%) were adopted to prepare β-nucleated iPP at a fixed final molten temperature (240°C) in this study. The crystallinity, polymorphic composition, and crystalline morphology were inspected in detail by a series of crystallographic characterizations, including calorimeter, X-ray diffraction, polarized light microscopy (PLM), and electron microscopy. Furthermore, the self-organization and re-crystallization behavior of β-nucleating agent occurred during cooling was characterized by rheometry. Finally, the dependence of mechanical properties, including tensile strength, elongation at break, and impact strength, on WBG content was discussed based on the variations in β-form content and crystalline morphology. Interestingly, it is found that while the WBG content is below 0.1 wt%, the toughness of β-nucleated iPP increases with increase in WBG content due to additional β-form content; as the WBG content is in range of 0.1–0.5 wt%, the toughness increases at a lower rate with increase in WBG content due to β-crystalline morphological change. However, a decrease in toughness is observed while nucleator content is above 0.5 wt% as WBG remains undissolved in iPP upon the adopted processing conditions. The result of this study provides valuable information for potential industrial applications. Copyright © 2010 John Wiley & Sons, Ltd.
Co-reporter:Run Su;Kun Jiang;Yao Ge;Shanwei Hu;Zhen Li;Xiuyun Li;Ke Wang;Qin Zhang;Fengxia Yang
Polymer International 2011 Volume 60( Issue 11) pp:1655-1662
Publication Date(Web):
DOI:10.1002/pi.3148
Abstract
It is feasible to control the phase morphology and orientation for immiscible polymer blends to manipulate their properties. In this paper, the blend of polyamide 1010 (PA1010) and isotactic polypropylene (iPP) (mainly at a fixed ratio of PA1010/iPP = 80/20) was used as an example to demonstrate the effect of shear on the morphology and resultant mechanical properties. After being melt blended, the injection-molded bars were prepared via a dynamic packing equipment to impose a prolonged shearing on the melts during the solidification stage. By controlling the shear time, the structure evolution and morphological development of the blends can be well controlled. Mechanical measurement of the molded bar showed a dramatically improved tensile property and impact strength with increasing shear time. Morphological examination revealed that the iPP droplets are elongated and become thin fibrils along the shear direction with increasing shear time. The shear-induced fibrillation, instead of orientation, is believed to be responsible for the largely improved properties of the blend, particularly for the impact strength. The toughening mechanism is discussed based on the combined effect of hindrance of crack propagation and the transferring and bearing of the load due to the existence of the fibrils. This was further proved by changing the blending ratio and using low molecular weight iPP. Finally, we propose a concept for designing blending materials with good comprehensive properties. Copyright © 2011 Society of Chemical Industry
Co-reporter:Hongwei Bai, Weiyi Zhang, Hua Deng, Qin Zhang, and Qiang Fu
Macromolecules 2011 Volume 44(Issue 6) pp:1233-1237
Publication Date(Web):February 14, 2011
DOI:10.1021/ma102439t
Co-reporter:Changyu Tang, Tiannan Zhou, Jinghui Yang, Qin Zhang, Feng Chen, Qiang Fu, Li Yang
Colloids and Surfaces B: Biointerfaces 2011 Volume 86(Issue 1) pp:189-197
Publication Date(Web):1 August 2011
DOI:10.1016/j.colsurfb.2011.03.041
Ultrasonication is often used to disperse nano-particles in aqueous solution. However, a good dispersion of nano-particles in aqueous solution is not always achieved, due to the fact that incoming ultrasonicwaves in liquid are usually reflected and damped at the gas/liquid interface. In this work, we report a so-called wet-grinding assisted ultrasonication (GU) method, in which wet-grinding of multi-walled carbon nanotubes (MWCNTs) in chitosan solution is carried out before ultrasonication. The dispersions of MWCNTs were characterized by visual comparison, UV/vis spectroscopy, and scanning electron microscopy (SEM). The results demonstrate that the dispersion quality of chitosan/MWCNT suspension prepared by wet-grinding assisted ultrasonication is much better than that by ultrasonication or wet-grinding alone. It was found that wet-grinding could improve the water wettability of MWCNTs and eliminate the barrier of air layer around MWCNTs to ultrasonicwaves. Meanwhile, the composite from the chitosan/MWCNTs suspension prepared by GU method has an obvious improvement in mechanical property compared to pure chitosan. This simple method for integrating MWCNTs and biocompatible chitosan into a homogeneous dispersion may have great potential application in biotechnology, such as preparing composite materials for medicine, bio-fiber, biosensor, antibacterial coating, and cell cultivation.Graphical abstractPristine MWCNT aggregates can be easily broken up into a number of individual nanotubes via ultrasonication, due to the improved water wettability of MWCNTs realized by wet-grinding with chitosan solution.Highlights► Chitosan/MWCNT suspension with good dispersion was prepared by wet-grinding assisted ultrasonication. ► Wet-grinding could improve the water wettability of MWCNTs and eliminate the barrier of air layer around MWCNTs to ultrasonicwaves. ► The composite from the chitosan/MWNTs suspension prepared by this method has an obvious improvement in mechanical property.
Co-reporter:Li Chen;Xin-lan Zhang;Huai-yuan Li;Bo Li;Ke Wang
Chinese Journal of Polymer Science 2011 Volume 29( Issue 1) pp:125-132
Publication Date(Web):2011 January
DOI:10.1007/s10118-010-1006-6
A simultaneous increase of both stiffness and extensibility of poly(ethylene glycol-co-cyclohexane-1,4-dimethanol terephthalate) (PETG)/polycarbonate (PC) blends prepared through the slit die extrusion-uniaxial cold stretching process was observed. The stretched sheets have a unique mechanical character that an increased tensile modulus is accompanied by an increased extensibility with increasing the draw ratio. Especially, a sharp increasing of the extensibility is observed for PETG/PC (70/30 wt%) blends at draw ratios between 8.2 and 20.0, where a nine times increase of extensibility is achieved. The mechanism of stretching-induced superior extensibility is investigated via micrograph observation, rheometry and calorimetric analysis. The observed superior extensibility could be tentatively explained by the bridging effect of the PC microfibrils on the crack development during tensile failure.
Co-reporter:Kun Jiang;Fei-long Yu;Run Su;Jing-hui Yang
Chinese Journal of Polymer Science 2011 Volume 29( Issue 4) pp:456-464
Publication Date(Web):2011 July
DOI:10.1007/s10118-011-1049-3
Thin wall samples of high density polyethylene (HDPE) were prepared via injection molding with different injection speeds ranging from 100 mm/s to 1200 mm/s. A significant decrease in the tensile strength and Young’s modulus was observed with increasing injection speed. In order to investigate the mechanism behind this decrease, the orientation, molecular weight, molecular weight distribution, melt flow rate, crystallinity and crystal morphology of HDPE were characterized using two-dimensional wide-angle X-ray diffraction (2D-WAXD), gel permeation chromatography (GPC), capillary rheometry and differential scanning calorimetry (DSC), respectively. It is demonstrated that the orientation, molecular weight, molecular weight distribution, melt flow rate and crystallinity have no obvious change with increasing injection speed. Nevertheless, the content of extended chain crystals or large folded chain crystals was found to decrease with increasing injection speed. Therefore, it is concluded that the decrease in tensile properties is mainly contributed by the reduced content of extended chain crystals or large folded chain crystals. This study provides industry with valuable information for the application of high speed injection molding.
Co-reporter:Dong-sheng Tan;Xiao-qing Zhang;Jian-chuan Wang
Chinese Journal of Polymer Science 2011 Volume 29( Issue 5) pp:615-626
Publication Date(Web):2011 September
DOI:10.1007/s10118-011-1071-5
A series of fluorinated phosphatidylcholine polyurethane macromolecular additives were synthesized by solution polymerization using methylenebis(phylene isocyanates) (MDI) and 1,4-butanediol (BDO) as hard segments, a new phoshporycholine, 2-(2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9-hexadecafluoro-10-(2-hydroxyethoxy)decyloxy) ethyl phosphorycholine (HDFOPC) as end-capper, and four polydiols, poly(tetramethylene glycol)s (PTMG), polydimethylsiloxane (PDMS), poly(1,6-hexyl-1,5-pentylcarbonate) (PHPC) and poly(propylene glycol) (PPG) as soft segments, respectively. The chemical structures of the synthesized polyurethanes were characterized by 1H-NMR and FTIR. DSC and DMA were employed to study the phase behavior of these novel polyurethanes due to their great influences on the surface properties, and hence their interactions with bio-systems. The results showed that phase separation of the fluorinated phosphatidylcholine end-capped polyurethanes was increased in comparison with that of normal polyurethanes. The effect of fluorinated phosphatidylcholine end-capped groups on the phase behavior was further demonstrated by analyzing the degree of hydrogen-bonding between hard and soft segments.
Co-reporter:Juan-juan Su;Guang-hui Yang;Cheng-zhen Geng
Chinese Journal of Polymer Science 2011 Volume 29( Issue 6) pp:
Publication Date(Web):2011 November
DOI:10.1007/s10118-011-1087-x
The effect of clay on the nucleating behavior of 1,3:2,4-bis(3,4-dimethylbenzylidene) sorbitol (DMDBS) in cryatallization of isotactic polypropylene (iPP) was investigated by means of differential scanning calorimetry (DSC), dynamic rheology and polarized light microscopy (PLM). It is interesting to note that the incorporation of layered clay nanoparticles into DMDBS-nucleated iPP may induce a synergetic nucleation effect while the DMDBS content is below 0.1 wt%, otherwise it restricts the crystallization rate prominently as the DMDBS content increases up to 0.3 wt%, which has exceeded the content threshold to yield a nucleating agent (NA) network. As shown by dynamic rheological investigations, the clay nanoparticles demonstrate an obstructive effect of disturbing the consistency of DMDBS fibrils network. Moreover, to further demonstrate the importance of NA network formation in the crystallization of iPP, we used another NA named HPN-20e, which can not form network structure at all over the concentration studied, for comparison. In this case, the nucleated-crystallization rate is independent on the addition of clay nanoparticles, as the nucleating mechanism is an individual nuclei manner without NA network forming.
Co-reporter:Hongwei Bai, Feng Luo, Tiannan Zhou, Hua Deng, Ke Wang, Qiang Fu
Polymer 2011 Volume 52(Issue 10) pp:2351-2360
Publication Date(Web):4 May 2011
DOI:10.1016/j.polymer.2011.03.017
Large amount of work has been reported on the annealing of polypropylene (PP) and the related changes in mechanical properties. However, the structure–property correlations and the physical origin of annealing induced microstructural evolution are still not very clear. In this work, taking β-form PP (β-PP) as example, the microstructural changes induced by annealing were investigated from macromolecular to crystalline lamellae level with Fourier transform infrared (FTIR) spectroscopy, conventional differential scanning calorimetry (DSC), temperature-modulated DSC (TMDSC), wide-angle X-ray diffraction (WAXD), small-angle X-ray scattering (SAXS) and dynamic mechanical analysis (DMA). Besides mobile amorphous fraction (MAF), the role of rigid amorphous fraction (RAF) in toughening PP is particularly taken into consideration. It is shown that annealing increases the chain mobility in MAF and decreases it in RAF. Such an effect is believed to be mainly associated with the formation of looser MAF and more RAF by the microstructural re-arrangement involving conformational ordering of partial amorphous chain segments and a significant interlamellae thickening. A thorough analysis of structure–property relationship through observing plastic deformation behaviors by scanning electron microscope (SEM) and estimating stress transmission between crystalline and amorphous phases, suggests that both MAF and RAF play important role on toughening β-PP. They can promote the initiation of microvoids effectively upon deformation by reducing the stress transmission. As a result, large-scale plastic deformation is triggered. This work is important and provides a new insight into the mechanisms of microstructural evolution and subsequent improvement in impact toughness during annealing.
Co-reporter:Jianchuan Wang, Chengzhen Geng, Feng Luo, Yanmei Liu, Ke Wang, Qiang Fu, Bobing He
Materials Science and Engineering: A 2011 528(7–8) pp: 3169-3176
Publication Date(Web):
DOI:10.1016/j.msea.2010.12.081
Co-reporter:Run Su, Zhen Li, Hongwei Bai, Ke Wang, Qin Zhang, Qiang Fu, Zhijie Zhang, Yongfeng Men
Polymer 2011 Volume 52(Issue 16) pp:3655-3660
Publication Date(Web):20 July 2011
DOI:10.1016/j.polymer.2011.06.016
In this work, we investigated the epitaxial crystallization and its determinant factor in the blends of high density polyethylene (HDPE) and a low crystallizable propylene-ethylene random copolymer (PPR) during injection molding. For PPR dominated blend (blended with 30 wt.% HDPE), epitaxial growth of HDPE on the PPR crystals can be achieved, as demonstrated by two-dimensional wide-angle X-ray diffraction and small-angle X-ray scattering measurements, though the crystallization of PPR was far behind that of HDPE component under quiescent conditions. In-situ shear infrared experiments indicated that PPR crystallized in advance mainly due to larger crystallization window and flow-induced crystallization acceleration. As for the blend with 70 wt.% HDPE, however, one could not observe epitaxy. Shear-induced crystallization of HDPE hindered its epitaxial growth. Once the formation of shish-kebab of HDPE was activated, the epitaxial growth would be suppressed to a large extent.
Co-reporter:Jinghui Yang, Jianchuan Wang, Qin Zhang, Feng Chen, Hua Deng, Ke Wang, Qiang Fu
Polymer 2011 Volume 52(Issue 21) pp:4970-4978
Publication Date(Web):29 September 2011
DOI:10.1016/j.polymer.2011.08.051
The polar crystalline phase is the most important crystal mode for poly(vinylidene fluoride) (PVDF); its high content is urgently desired in the large-scale processing fabrication likes injection-molding. In this study, we proposed a convenient pathway to achieve large amount of polar phase in injection-molding part through cooperation of exerting oscillatory shear field and adding nanoclay. The effects of these two factors on the polymorphic composition were well demonstrated by infrared spectroscopy and X-ray diffraction. The increment of polar phase content was limited when shear field was solely imposed or only less amount of nanoclay, 1 wt%, was added. Whereas, by simultaneously exerting shear field and adding 1 wt% nanoclay, an extremely high polar phase fraction was achieved. So a positive cooperative effect of shear and nanoclay on the formation of polar phase can be proved absolutely. The simultaneously exerting shear and adding nanoclay leaded to not only high content of polar phase but also highly oriented structure. With this unique structure, an order-of-magnitude increase in the ductility (elongation) as well as good piezoelectric property has been achieved for the molded parts of PVDF/nanoclay nanocomposites.
Co-reporter:Xia Jiang;Kunjie Wang;Mingming Ding
Journal of Materials Science: Materials in Medicine 2011 Volume 22( Issue 4) pp:819-827
Publication Date(Web):2011 April
DOI:10.1007/s10856-011-4265-z
Gly-Arg-Gly-Asp-Ser-Pro (GRGDSP) peptide has frequently been used in the biomedical materials to enhance adhesion and proliferation of cells. In this work, we modified the nontoxic biodegradable waterborne polyurethanes (WBPU) with GRGDSP peptide and fabricated 3-D porous scaffold with the modified WBPU to investigate the effect of the immobilized GRGDSP peptide on human umbilical vein endothelial cells (HUVECs) adhesion and proliferation. A facile and reliable approach was first developed to quantitative grafting of GRGDSP onto the WBPU molecular backbone using ethylene glycol diglycidyl ether (EX810) as a connector. Then 3-D porous WBPU scaffolds with various GRGDSP content were fabricated by freeze-drying the emulsion. In both of the HUVECs adhesion and proliferation tests, enhanced cell performance was observed on the GRGDSP grafted scaffolds compared with the unmodified scaffolds and the tissue culture plate (TCP). The adhesion rate and proliferation rate increased with the increase of GRGDSP content in the scaffold and reached a maximum with peptide concentration of 0.85 μmol/g based on the weight of the polyurethanes. These results illustrate the necessity of the effective control of the GRGDSP content in the modified WBPU and support the potential utility of these 3-D porous modified WBPU scaffolds in the soft tissue engineering to guide cell adhesion, proliferation and tissue regeneration.
Co-reporter:Li Chen;Yu-fang Xiang;Ke Wang;Qin Zhang
Chinese Journal of Polymer Science 2011 Volume 29( Issue 3) pp:377-389
Publication Date(Web):2011 May
DOI:10.1007/s10118-011-1035-9
Three types of high-density polyethylene (HDPE) with different molecular weights (high, medium and low) were adopted to evaluate the influence of matrix molecular weight on the structure-property relation of injection-molded HDPE/mica composites through a combination of SEM, 2d-WAXS, DSC, DMA and tensile testing. Various structural factors including orientation, filler dispersion, interfacial interaction between HDPE and mica, etc., which can impact the macroscopic mechanics, were compared in detail among the three HDPE/mica composites. The transcrystallization of HDPE on the mica surface was observed and it exhibited strong matrix molecular weight dependence. Obvious transcrystalline structure was found in the composite with low molecular weight HDPE, whereas it was hard to be detected in the composites with increased HDPE molecular weight. The best reinforcement effect in the composite with low molecular weight HDPE can be understood as mainly due to substantially improved interfacial adhesion between matrix and mica filler, which arises from the transcrystallization mechanism.
Co-reporter:Meng Ma, Zhoukun He, Jinghui Yang, Qi Wang, Feng Chen, Ke Wang, Qin Zhang, Hua Deng, and Qiang Fu
Langmuir 2011 Volume 27(Issue 3) pp:1056-1063
Publication Date(Web):January 7, 2011
DOI:10.1021/la104003p
Thin films of an amorphous polymer, polystyrene (PS), and a crystalline polymer, poly(ε-caprolactone) (PCL), blend were prepared by spin coating a toluene solution. Surface chemical compositions of the blend films were measured by X-ray photoelectron spectroscopy (XPS), and the surface and interface topographical changes were followed by atomic force microscopy (AFM). By changing the PS concentration and keeping the PCL concentration of the solution at 1 wt %, a great variety of morphologies were constructed. The results show that the morphology of the blend films can be divided into three regions with increasing PS concentration. In region I, PS island domains are embedded in PCL crystals when the PS concentration is lower than 0.3 wt % and the size of the PS island increases with increasing PS concentration. In region II, holes with different sizes surrounded by a low rim are obtained when the concentration of PS is between 0.35 and 0.5 wt %. After selectively washing the PS domains, we studied the interface morphology of PS/PCL and found that the upper PS-rich layer extended into the bottom PCL layer, forming a trench surrounding the holes. In region III, an enriched two-layer structure with the PS-rich layer on top of the blend films and the PCL-rich crystal layer underneath is obtained when the concentration of PS is higher than 0.5 wt %. Last, the formation mechanism of the different surface and interface morphologies is further discussed in terms of the vertical phase separation to a layered structure, followed by liquid−liquid dewetting and crystallization processes during spin coating.
Co-reporter:Meng Ma, Zhoukun He, Jinghui Yang, Feng Chen, Ke Wang, Qin Zhang, Hua Deng, and Qiang Fu
Langmuir 2011 Volume 27(Issue 21) pp:13072-13081
Publication Date(Web):September 21, 2011
DOI:10.1021/la2036289
In this Article, the morphological evolution in the blend thin film of polystyrene (PS)/poly(ε-caprolactone) (PCL) was investigated via mainly AFM. It was found that an enriched two-layer structure with PS at the upper layer and PCL at the bottom layer was formed during spinning coating. By changing the solution concentration, different kinds of crystal morphologies, such as finger-like, dendritic, and spherulitic-like, could be obtained at the bottom PCL layer. These different initial states led to the morphological evolution processes to be quite different from each other, so the phase separation, dewetting, and crystalline morphology of PS/PCL blend films as a function of time were studied. It was interesting to find that the morphological evolution of PS at the upper layer was largely dependent on the film thickness. For the ultrathin (15 nm) blend film, a liquid–solid/liquid–liquid dewetting–wetting process was observed, forming ribbons that rupture into discrete circular PS islands on voronoi finger-like PCL crystal. For the thick (30 nm) blend film, the liquid–liquid dewetting of the upper PS layer from the underlying adsorbed PCL layer was found, forming interconnected rim structures that rupture into discrete circular PS islands embedded in the single lamellar PCL dendritic crystal due to Rayleigh instability. For the thicker (60 nm) blend film, a two-step liquid–liquid dewetting process with regular holes decorated with dendritic PCL crystal at early annealing stage and small holes decorated with spherulite-like PCL crystal among the early dewetting holes at later annealing stage was observed. The mechanism of this unusual morphological evolution process was discussed on the basis of the entropy effect and annealing-induced phase separation.
Co-reporter:Mingming Ding, Xueling He, Zhigao Wang, Jiehua Li, Hong Tan, Hua Deng, Qiang Fu, Qun Gu
Biomaterials 2011 32(35) pp: 9515-9524
Publication Date(Web):
DOI:10.1016/j.biomaterials.2011.08.074
Co-reporter:Feng Luo, Jinwen Wang, Hongwei Bai, Ke Wang, Hua Deng, Qin Zhang, Feng Chen, Qiang Fu, Bing Na
Materials Science and Engineering: A 2011 528(22–23) pp: 7052-7059
Publication Date(Web):
DOI:10.1016/j.msea.2011.05.030
Co-reporter:Lijuan Zhou, Lunquan Yu, Mingming Ding, Jiehua Li, Hong Tan, Zhigao Wang, and Qiang Fu
Macromolecules 2011 Volume 44(Issue 4) pp:857-864
Publication Date(Web):January 19, 2011
DOI:10.1021/ma102346a
To obtain a pH-sensitive multifunctional polyurethane micelle drug carrier, a novel pH-sensitive macrodiol containing acid-cleavable hydrazone linkers, poly(ε-caprolactone)−hydrazone−poly(ethylene glycol)−hydrazone−poly(ε-caprolactone) diol (PCL−Hyd−PEG−Hyd−PCL), was synthesized and characterized with proton nuclear magnetic resonance spectra (1H NMR). A series of pH-sensitive biodegradable polyurethanes (pHPUs) were designed and synthesized using pH-sensitive macrodiol, l-lysine ethyl ester diisocyanate (LDI) and l-lysine derivative tripeptide as chain extender, which can provide an active reaction site for the development of positive target polyurethane micelles for drug delivery. The bulk structures of the prepared polyurethanes were carefully characterized with 1H NMR, gel permeation chromatograph (GPC), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FT-IR). The polyurethanes could be cleaved in acidic media (pH ∼ 4−6) as well as degraded in PBS and enzymatic solution, as demonstrated by 1H NMR and weight loss, respectively. The cytotoxicity of their degradation products was evaluated using methylthiazoletetrazolium (MTT) assay in vitro, resulting in no apparent inhibition effect on the fibroblasts. These polyurethanes could self-assemble into micelles in aqueous solutions, as verified using dynamic light-scattering (DLS). Our present work provides a new method for the preparation of amphiphilic multiblock polyurethanes with pH-sensitivity and biodegradability. It could be a good candidate as biodegradable multifunctional carrier for active intracellular drug delivery.
Co-reporter:Hua Deng;Tetyana Skipa;Emiliano Bilotti;Rui Zhang;Dirk Lellinger;Luca Mezzo;Ingo Alig;Ton Peijs
Advanced Functional Materials 2010 Volume 20( Issue 9) pp:1424-1432
Publication Date(Web):
DOI:10.1002/adfm.200902207
Abstract
A general method is described to prepare high-performance conductive polymer fibers or tapes. In this method, bicomponent tapes/fibers containing two layers of conductive polymer composites (CPCs) filled with multiwall carbon nanotubes (MWNT) or carbon black (CB) based on a lower-melting-temperature polymer and an unfilled polymer core with higher melting temperature are fabricated by a melt-based process. Morphological control of the conductive network formed by nanofillers is realized by solid-state drawing and annealing. Information on the morphological and electrical change of the highly oriented conductive nanofiller network in CPC bicomponent tapes during relaxation, melting, and crystallization of the polymer matrix is reported for the first time. The conductivity of these polypropylene tapes can be as high as 275 S m−1 with tensile strengths of around 500 MPa. To the best of the authors' knowledge, it is the most conductive, high-strength polymer fiber produced by melt-processing reported in literature, despite the fact that only ∼5 wt.% of MWNTs are used in the outer layers of the tape and the overall MWNT content in the bicomponent tape can be much lower (typically ∼0.5 wt.%). Their applications could include sensing, smart textiles, electrodes for flexible solar cells, and electromagnetic interference (EMI) shielding. Furthermore, a modeling approach was used to study the relaxation process of highly oriented conductive networks formed by carbon nanofillers.
Co-reporter:Run Su, Ke Wang, Nanying Ning, Feng Chen, Qin Zhang, Chaoyu Wang, Qiang Fu, Bing Na
Composites Science and Technology 2010 Volume 70(Issue 4) pp:685-691
Publication Date(Web):April 2010
DOI:10.1016/j.compscitech.2010.01.001
In this article, a quantitative measurement of orientation functions for both the polymer matrix and the filler has been carried out, for the first time, in high-density polyethylene (HDPE)/inorganic whisker (SMCW) composite fibers, with aid of polarized Fourier transform infrared (FTIR) spectroscopy. A highly oriented structure was observed in the as-spun fibers, and the orientation functions of both polyethylene and the whisker decreased with the increase of whisker content. During tensile deformation of the fibers, the orientation functions were continuously enhanced as increasing of the strain for the matrix and the filler. However, a fast increase of orientation was found for pure polyethylene fiber and composite fibers with less whisker content, and a slow increase for composite fibers with higher whisker content. Very interestingly, a formation of hybrid shish-kebab structure with whisker acting as shish and polyethylene lamellae as kebab was observed in the as-spun fiber with low loading of whisker (less than 10 wt.%), resulting in a strong interfacial interaction between polyethylene and whisker. As a result, the highest tensile strength was observed in this sample even it had a lower orientation compared with that of pure HDPE. For the composite fiber with 10 and 20 wt.% whisker, no obvious formation of hybrid shish-kebab was observed, resulting in a poor interfacial interaction and subsequently, lower tensile strength. That result indicates that the tensile strength of the fibers depends not only on the orientations of the polyethylene and the whisker, more importantly, on the interfacial interaction between matrix and the filler. The change of orientations of the composite fibers by adding whisker and the formation of hybrid shish-kebab structure were discussed based on rheological measurement.
Co-reporter:Mingming Ding, Lijuan Zhou, Xiaoting Fu, Hong Tan, Jiehua Li and Qiang Fu
Soft Matter 2010 vol. 6(Issue 9) pp:2087-2092
Publication Date(Web):31 Mar 2010
DOI:10.1039/B926689E
Unique self-assembly behavior of novel nontoxic gemini cationic biodegradable multiblock poly(ε-caprolactone urethane)s which contain both gemini quaternary ammonium and PEG groups is firstly reported. The micellar size, size distributions, zeta potential, CMC and Kv could be well-tailored for application in drug and gene delivery.
Co-reporter:Qi Wang, Jinghui Yang, Weiwei Yao, Ke Wang, Rongni Du, Qin Zhang, Feng Chen, Qiang Fu
Applied Surface Science 2010 Volume 256(Issue 20) pp:5843-5848
Publication Date(Web):1 August 2010
DOI:10.1016/j.apsusc.2010.03.057
Abstract
Self-assembly of block copolymer is an effective strategy to prepare periodic structures at nanoscale. In this paper an unique and very simple method to prepare inorganic silica nanopattern is demonstrated from self-assembling of poly(styrene-block-dimethylsiloxane) (PS-b-PDMS) on the surface of silicon wafer. To simplify the patterning process, at first we obtain highly ordered PDMS microdomains, which are covered with PS layer by controlling solvent vapor annealing conditions. Following exposure to UV/O3 irradiation, nanopatterned surface consisting of silicon oxide is fabricated directly via selectively etching PS phase and converting PDMS phase into silicon oxide. As tuning the composition of the block copolymer, hexagonally packing dot and straight stripe pattern can be obtained. Finally, the time evolution from spheres morphology to aligned long cylinders is discussed. These results hold promise for nanolithography and the fabrication of nanodevices.
Co-reporter:Ping Luo;Kun Jiang;Ke Wang;Jinghui Yang;Tao Xu;Li Chen
Polymer International 2010 Volume 59( Issue 2) pp:198-203
Publication Date(Web):
DOI:10.1002/pi.2707
Abstract
The introduction of carbon nanotubes in a polymer matrix can markedly improve its mechanical properties and electrical conductivity, and much effort has been devoted to achieve homogeneous dispersions of carbon nanotubes in various polymers. Our group previously performed successfully fluorine-grafted modification on the sidewalls of multi-walled carbon nanotubes (MWCNTs), using homemade equipment for CF4 plasma irradiation. As a continuation of our previous work, in the present study CF4 plasma-treated MWCNTs (F-MWCNTs) were used as a nanofiller with poly(ethylene terephthalate) (PET), which is a practical example of the application of such F-MWCNTs to prepare polyester/MWCNTs nanocomposites with ideal nanoscale structure and excellent properties. As confirmed from scanning electron microscopy observations, the F-MWCNTs could easily be homogeneously dispersed in the PET matrix during the in situ polymerization preparation process. It was found that a very low content of F-MWCNTs dramatically altered the crystallization behavior and mechanical properties of the nanocomposites. For example, a 15 °C increase in crystallization temperature was achieved by adding only 0.01 wt% F-MWCNTs, implying that the well-dispersed F-MWCNTs act as highly effective nucleating agents to initiate PET crystallization at high temperature. Meanwhile, an abnormal phenomenon was found in that the melt point of the nanocomposites is lower than that of the pure PET. The mechanism of the tailoring of the properties of PET resin by incorporation of F-MWCNTs is discussed, based on structure–property relationships. The good dispersion of the F-MWCNTs and strong interfacial interaction between matrix and nanofiller are responsible for the improvement in mechanical properties and high nucleating efficiency. The abnormal melting behavior is attributed to the recrystallization transition of PET occurring at the early stage of crystal melting being retarded on incorporation of F-MWCNTs. Copyright © 2009 Society of Chemical Industry
Co-reporter:Long Chen;Jinghui Yang;Ke Wang;Feng Chen
Polymer International 2010 Volume 59( Issue 8) pp:
Publication Date(Web):
DOI:10.1002/pi.2843
Abstract
Poly(L-lactic acid) (PLLA) has good biocompatibility, biodegradability and physical properties. However, one of the drawbacks of PLLA is its brittleness due to the stiff backbone chain. In this work, a largely improved tensile toughness (extensibility) of PLLA was achieved by blending it with poly(ε-caprolactone) (PCL). To obtain a good dispersion of PCL in the PLLA matrix, blends were prepared via a solution-coagulation method. An increase in extensibility of PLLA of more than 20 times was observed on adding only 10 wt% of PCL, accompanied by a slight decrease in tensile strength. However, annealing of the samples led to a sharp decrease of extensibility due to phase separation and a change of crystalline structure. To conserve the good mechanical properties of PLLA/PCL blends, the blends were crosslinked via addition of dicumyl peroxide during the preparation process. For the crosslinked blend films, the extensibility was maintained nearly at the original high value even after annealing. Morphological analysis of cryo-fractured and etched-smoothed surfaces of the PLLA/PCL blends was carried out using scanning electron microscopy. Differential scanning calorimetry and polarized light microscopy experiments were used to check the possible change of crystallinity, melting point and crystal morphology for both PLLA and PCL after annealing. The results indicated that the combination of solution-coagulation and crosslinking resulted in a good and stable dispersion of PCL in the PLLA matrix, which is considered as the main reason for the observed improvement of tensile toughness. Copyright © 2010 Society of Chemical Industry
Co-reporter:Yufang Xiang;Zaichuan Hou;Run Su;Ke Wang
Polymers for Advanced Technologies 2010 Volume 21( Issue 1) pp:48-54
Publication Date(Web):
DOI:10.1002/pat.1355
Abstract
The interfacial interaction and orientation of filler play important roles in the enhancement of mechanical performances for polymer/inorganic filler composites. Shear has been found to be a very effective way for the enhancement of interfacial interaction and orientation. In this work, we will report our recent efforts on exploring the development of microstructure of high density polyethylene (HDPE)/mica composites in the injection-molded bars obtained by so-called dynamic packing injection molding (DPIM), which imposed oscillatory shear on the melt during the solidification stage. The mechanical properties were evaluated by tensile testing and dynamic mechanical analysis (DMA), and the crystal morphology, orientation, and the dispersion of mica were characterized by scanning electron microscopy and two-dimensional wide-angle X-ray scattering. Compared with conventional injection molding, DPIM caused an obvious increase in orientation for both HDPE and mica. More importantly, better dispersion and epitaxial crystallization of HDPE was observed on the edge of the mica in the injection-molded bar. As a result, increased tensile strength and modulus were obtained, accompanied with a decrease of elongation at break. The obtained data were treated by Halpin–Tsai model, and it turned out that this model could be also used to predict the stiffness of oriented polymer/filler composites. Copyright © 2009 John Wiley & Sons, Ltd.
Co-reporter:Xinlan Zhang;Ke Wang;Bo Li;Feng Chen
Polymers for Advanced Technologies 2010 Volume 21( Issue 6) pp:401-407
Publication Date(Web):
DOI:10.1002/pat.1442
Abstract
In this paper, an elastomer containing epoxy groups, ethylene-butylacrylate-glycidylmethacrylate (PTW), was used as toughening modifier for the poly(ethylene glycol-co-cyclohexane-1,4-dimethanol terephthalate) (PETG)/polycarbonate (PC) blends. A remarkable improvement of toughness was achieved by addition of only 5 wt% PTW. In particular, an obvious brittle–ductile (B–D) transition in impact toughness was found when the PTW content increased from 3 to 5 wt%. The toughening mechanism and observed B–D transition have been explored in detail, combining with electronic microscopy observation, melt rheological investigation and dynamic mechanical analysis (DMA). It is suggested that the B–D transition can be attributed to a better interfacial adhesion between different phases, and importantly, to a continuum percolation dispersed-phases network formed at appropriate PTW content, in which PC particles are connected with each other by PTW phase. Our present study offers new, profound insight on the toughening mechanism for the elastomer modified amorphous/amorphous plastic blends. Copyright © 2009 John Wiley & Sons, Ltd.
Co-reporter:Jinghui Yang, Ke Wang, Hua Deng, Feng Chen, Qiang Fu
Polymer 2010 Volume 51(Issue 3) pp:774-782
Publication Date(Web):5 February 2010
DOI:10.1016/j.polymer.2009.11.059
Injection-molded products usually show hierarchical structure from skin to core due to the existence of shear gradient and temperature gradient. Investigating the hierarchical structure is helpful to better understand the structure-property relationship of injection-molded sample, which is important for design and preparation of polymer products with high performance. In this work, the hierarchical structures of injection-molded bars of high-density polyethylene (HDPE)/multi-walled carbon nanotubes (MWCNTs) composite were explored by examining the microstructure and crystal morphology, layer by layer, along the sample thickness, using SEM, DSC and 2D-WAXS. To enhance the shear effect, a so-called dynamic packing injection molding (DPIM) technique was used to prepare the molded bar with high orientation level. Interestingly, SEM revealed that in the skin and core zones, the lamellae of PE anchored randomly on the surface of MWCNTs, while well-defined nanohybrid shish–kebab (NHSK) entities, in which fibrillous carbon nanotubes (CNTs) act as shish while HDPE lamellae act as kebab, exist in the oriented zone. The changed NHSK crystal structure along the thickness direction of molded bar is considered as due to the shear gradient and thermal gradient in injection molding. And the underlying origin of in situ formation of NHSK under shear effects is discussed based on experimental observations.
Co-reporter:Bing Na, Ruihua Lv, Shufen Zou, Zhujun Li and Nana Tian, Qiang Fu
Macromolecules 2010 Volume 43(Issue 4) pp:1702-1705
Publication Date(Web):January 27, 2010
DOI:10.1021/ma100012c
Co-reporter:Bing Na, Nana Tian, Ruihua Lv, Shufen Zou and Wenfei Xu, Qiang Fu
Macromolecules 2010 Volume 43(Issue 2) pp:1156-1158
Publication Date(Web):December 15, 2009
DOI:10.1021/ma902522v
Co-reporter:Bing Na, Nana Tian, Ruihua Lv, Zhujun Li, Wenfei Xu, Qiang Fu
Polymer 2010 Volume 51(Issue 2) pp:563-567
Publication Date(Web):21 January 2010
DOI:10.1016/j.polymer.2009.11.064
The structural development during cold crystallization of poly (l-lactide) has been explored by time-dependent Fourier transform infrared spectroscopy and depolarized light scattering, respectively. It is indicated that the conformation-sensitive 956 cm−1 band changes first during induction period, followed by formation of 103 helix sequence (921 cm−1 band) in the disordered crystals; after that, the inner structure of new-formed disordered crystals is further perfected, giving rise to frequency shift of 871 cm−1 band to higher wavenumber. Moreover, the formation and subsequent perfection of disordered crystals are also evidenced by the sharp transition of integrated scattering intensity revealed by depolarized light scattering measurements. It is strongly suggested that the cold crystallization of poly (l-lactide) follows a sequential ordering or multi-step process at atomic scale. Furthermore, such a sequential ordering is independent of crystallization temperature and the thermal history (melt cooling rate) of samples prior to cold crystallization. Increasing crystallization temperature or decreasing melt cooling rate just shortens the onset time related to above-referred each step.
Co-reporter:Jing Cao;Ke Wang;Hong Yang;Feng Chen;Qin Zhang
Journal of Polymer Science Part B: Polymer Physics 2010 Volume 48( Issue 3) pp:302-312
Publication Date(Web):
DOI:10.1002/polb.21881
Abstract
In current study, a real-time rheological method was used to investigate the intercalation and exfoliation process of clay in high-density polyethylene/organoclay (HDPE/OMMT) nanocomposites using maleic anhydride grafted polyethylene (PEgMA) as compatibilizer. To do this, a steady shear was applied to the original nonintercalated or slightly intercalated composites prepared via simple mixing. The moduli of the composites were recorded as a function of time. The effect of matrix molecular weight and the content of compatibilizer on the modulus were studied. The role of the compatibilizer is to enhance the interaction between OMMT and polymer matrix, which facilitates the dispersion, intercalation, and exfoliation of OMMT. The matrix molecular weight determines the melt viscosity and affects the shear stress applied to OMMT platelets. Based on the experimental results, different exfoliation processes of OMMT in composites with different matrix molecular weight were demonstrated. The slippage of OMMT layers is suggested in low-molecular weight matrix, whereas a gradual intercalation process under shear is suggested in high-molecular weight matrix. Current study demonstrates that real-time rheological measurement is an effective way to investigate the dispersion, intercalation, and exfoliation of OMMT as well as the structural change of the matrix. Moreover, it also provides a deep understanding for the role of polymer matrix and compatibilizer in the clay intercalation process. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 302–312, 2010
Co-reporter:Jiehua Li, Dongsheng Tan, Xiaoqing Zhang, Hong Tan, Mingming Ding, Changxiu Wan, Qiang Fu
Colloids and Surfaces B: Biointerfaces 2010 Volume 78(Issue 2) pp:343-350
Publication Date(Web):1 July 2010
DOI:10.1016/j.colsurfb.2010.03.027
In this study, a surface grafting of nonfouling poly(ethylene glycol) methyl ether acrylate (PEGMA) on poly(ethylene terephthalate) (PET) was carried out via surface-initiated atom-transfer radical polymerization (SI-ATRP) to improve hemocompatibility of polymer based biomaterials. To do this, the coupling agent with hydroxyl groups for the ATRP initiator was first anchored on the surface of PET films using photochemical method, and then these hydroxyl groups were esterified by bromoisobutyryl bromide, from which PET with various main chain lengths of PEGMA was prepared. The structures and properties of modified PET surfaces were investigated using water contact angle (WAC), ATR-FTIR, X-ray photoelectron spectroscopy (XPS) and Atomic force microscopy (AFM). The molecular weights of the free polymer from solution were determined by gel permeation chromatography (GPC). These results indicated that grafting of PEGMA on PET film is a simple way to change its surface properties. The protein adsorption resistance on the surfaces of PET was primarily evaluated by an enzyme-linked immunosorbent assay (ELISA). The result demonstrated that the protein adsorption could be well suppressed by poly(PEGMA) brush structure on the surface of PET. This work provides a new approach for polymers to enhance their biocompatibility.
Co-reporter:Run Su;Ke Wang;Qin Zhang 张琴;Feng Chen 傅强
Chinese Journal of Polymer Science 2010 Volume 28( Issue 2) pp:249-255
Publication Date(Web):2010 March
DOI:10.1007/s10118-010-9013-1
The phase morphology and thermal behavior of various isotactic polypropylene (PP)/linear low density polyethylene (LLDPE) blends were investigated with aid of scanning electron microscopy (SEM) and differential scanning calorimetry (DSC), respectively. The effect of barrel (melt) temperature on the morphology, thermal behavior and the resultant mechanical properties of the injection molded bars was the research focus, and the influence of LLDPE composition was also taken into account. It was found that the mechanical properties, especially the tensile ductility and the impact strength, were greatly affected by the processing temperature. The samples obtained at low temperatures had the highest elongation at break and impact strength, while those molded at high temperatures had the poorest toughness. Two reasons were responsible for that: first, the phase size in the samples increased with the processing temperature; second, possible orientation existed in the samples obtained at low processing temperatures.
Co-reporter:Tian-nan Zhou;Hong Yang;Nan-ying Ning
Chinese Journal of Polymer Science 2010 Volume 28( Issue 1) pp:
Publication Date(Web):2010 January
DOI:10.1007/s10118-010-8217-8
A relatively high predetermined crystallization temperature (135°C) was chosen to grow well developed iPP spherulites, then the partial melting was carried out at a temperature of 165°C, where the preformed spherulites were seen to only decrease their size but not completely melted. The crystallization behavior of partially melted isotactic polypropylene (iPP) has been carefully examined by different scanning calorimetry (DSC) and polarized light microscopy (PLM). The experimental results show that at a special annealing temperature (165°C) the melting behavior of iPP includes two parts with different mechanism, one part is the melting of iPP spherulite outside, another is the partial lamellae perfection during longer annealing time in the unmelted spherulite. The conformational orders of the iPP melt decrease with the increase of the annealing temperature.
Co-reporter:Run Su, Zeqi Zhang, Xiang Gao, Yao Ge, Ke Wang and Qiang Fu
The Journal of Physical Chemistry B 2010 Volume 114(Issue 31) pp:9994-10001
Publication Date(Web):July 19, 2010
DOI:10.1021/jp1020802
A macroscopic bamboo-like bionic structure was fabricated in the injection-molded bar of isotactic polypropylene via the combined effect of “melt manipulation” and β-nucleator. Such structure consists of strengthened shell zone with high orientation and low β-phase amount, and toughened core part with isotropic texture and dominant β-modification. The influences of shear intensity on structural hierarchies, polymorphism, and crystalline morphology were estimated. Both toughness and strength can be significantly improved with increasing shear intensity on the bamboo-like structure. Our study suggested an alternative approach to achieve excellent comprehensive mechanics in polypropylene via macroscopic structural design during the practical molding process.
Co-reporter:Fang Mai, Ke Wang, Meijun Yao, Hua Deng, Feng Chen and Qiang Fu
The Journal of Physical Chemistry B 2010 Volume 114(Issue 33) pp:10693-10702
Publication Date(Web):August 2, 2010
DOI:10.1021/jp1019944
The formation of a shish kebab (SK) structure, where carbon nanotubes (CNTs) serve as shish and polymer lamellae serve as kebab, is particularly interesting and provides a novel way to enhance the polymer−CNT interface. A fine SK structure is achieved through melt spinning. High density polyethylene and pristine CNTs were first compounded in an extruder. The compound was then spun into fibers with different draw ratios with the aid of a capillary rheometer. The crystalline structure and mechanical behavior were characterized by scanning electron microscopy, differential scanning calorimetry, two-dimensional wide-angle X-ray scattering, polarized Raman spectroscopy, and tensile testing. An increase in tensile strength as high as 3 times has been achieved in the fiber. The formation of SKs is considered as the main mechanism responsible for the enhanced interfacial interaction and excellent tensile property.
Co-reporter:Changyu Tang, Qin Zhang, Ke Wang, Qiang Fu, Chaoliang Zhang
Journal of Membrane Science 2009 Volume 337(1–2) pp:240-247
Publication Date(Web):15 July 2009
DOI:10.1016/j.memsci.2009.03.048
In this work, the effects of MWNTs content on water transport behaviors and tensile properties of prepared chitosan porous membranes were investigated. In the case of chitosan membrane using low molecular weight PEG6000 as a porogen, a percolation-like behavior of water transport rate was observed for the first time in composite membranes with a critical MWNTs content (5 wt%). The water flux of composite membrane with 10 wt% MWNTs (128.1 L/m2 h) is 4.6 times that of neat one (27.6 L/m2 h). This could be understood as due to the formation of MWNTs network located among the pore network of chitosan membrane at high MWNTs content, where the hollow nanochannel of MWNTs and their interspaces could provide a new transport channel for water. In contrary, when high molecular weight PEG10000 is used as the porogen, a decreased water flux of the prepared composite membrane is found with increase of MWNTs content. In this case, a strong compatibilizing effect of MWNTs on chitosan/PEG10000 blends is observed, resulting in a decreased pore size and poor water flux of the membranes. Furthermore, a greatly improved tensile strength of chitosan porous membranes has been achieved by adding MWNTs, no matter which molecular weight PEG is used as porogen. Our work provides a novel way to improve water flux and/or control the pore size of polymer porous membranes by using MWNTs.
Co-reporter:Li Cui, Jen-Taut Yeh, Ke Wang, Fang-Chang Tsai, Qiang Fu
Journal of Membrane Science 2009 Volume 327(1–2) pp:226-233
Publication Date(Web):5 February 2009
DOI:10.1016/j.memsci.2008.11.027
A series of nylon 6-clay nanocomposite (NYC)/poly(vinyl alcohol) (PVA) blends films were prepared via melt compounding and pressing. The good compatibility between NYC and PVA was approved by DMA and FT-IR measurements. The macroscopic barrier properties of NYC/PVA blends films were inspected in detail, based on a microscopic free volume view of point. The gasoline permeation properties and the characterized parameters of free volume were adjusted through varying the PVA content. A similarity was found between barrier properties vs. PVA content and free volume parameters vs. PVA content. The relation between free volume fraction and permeability coefficient could be described exactly as an exponent function, implied that microscopic free volume plays an important role on determining macroscopic barrier properties.
Co-reporter:Jinghui Yang, Tao Xu, Ai Lu, Qin Zhang, Hong Tan, Qiang Fu
Composites Science and Technology 2009 Volume 69(Issue 2) pp:147-153
Publication Date(Web):February 2009
DOI:10.1016/j.compscitech.2008.08.030
In this paper, electrical and mechanical properties of Poly (p-phenylene sulfide) (PPS)/multi-wall carbon nanotubes (MWNTs) nanocomposites were reported. The composites were obtained just by simply melt mixing PPS with raw MWNTs without any pre-treatment. The dispersion of MWNTs and interfacial interaction were investigated through SEM &TEM and Raman spectra. The rheological test and crystallization behavior were also investigated to study the effects of MWNTs concentration on the structure and chain mobility of the prepared composites. Though raw MWNTs without any pre-treatment were used, a good dispersion and interaction between PPS and MWNTs have been evidenced, resulting in a great improvement of electrical properties and mechanical properties of the composites. Raman spectra showed a remarkable decrease of G band intensity and a shift of D bond, demonstrating a strong filler–matrix interaction, which was considered as due to π–π stacking between PPS and MWNTs. The storage modulus (G′) versus frequency curve presented a plateau above the percolation threshold of about 2–3 wt% with the formation of an interconnected nanotube structure, indicative of ‘pseudo-solid-like’ behavior. Meanwhile, a conductive percolation threshold of 5 wt% was achieved and the conductivity of nanocomposites increased sharply by several orders of magnitude. The difference between electrical and rheological percolation threshold, and the effect of critical percolation on the chain mobility, especially on crystallization behavior of PPS, were discussed. In summary, our work provides a simple and fast way to prepare PPS/MWNTs nanocomposites with good dispersion and improved properties.
Co-reporter:Run Su, Juanxia Su, Ke Wang, Changyue Yang, Qin Zhang, Qiang Fu
European Polymer Journal 2009 Volume 45(Issue 3) pp:747-756
Publication Date(Web):March 2009
DOI:10.1016/j.eurpolymj.2008.12.009
It is feasible to control the phase morphology and phase inversion for immiscible polymer blends to manipulate their properties. In this work, the blend of high-density polyethylene (HDPE)/polyoxymethylene (POM) was used as an example, to demonstrate the effect of shear on the phase morphology and resultant mechanical properties in immiscible polymer blends. To do so, a well defined “in-process morphology control” process during injection molding was conducted. That was: after making the blends via melt mixing, the injection-molded bars were prepared via a so-called dynamic packing injection molding equipment to impose a prolonged shearing on the melts during the solidification stage. Phase morphologies and crystal structures of the blends were estimated mainly through scanning electron microscopy, differential scanning calorimetry and 2D wide-angle X-ray scattering, respectively. For in-process morphology controlled samples, co-continuous structures, especially subinclusions inside another continuous phase induced by shear, were observed when the HDPE content was between 30 wt% and 50 wt%, leading to much early occurrence of phase inversion and also the lowest degree of orientation for both HDPE and POM. However, for samples obtained via conventional injection molding, a droplet morphology was always observed with HDPE dispersed in POM as the content of HDPE was up to 30 wt%, but with POM dispersed in HDPE as the content of HDPE was 50 wt%. The performances of injection-molded bars were mainly respect to the phase morphologies for samples obtained via conventional injection molding in which tensile properties continuously decreased with increasing of HDPE content up to 30 wt% and then increased with further increasing of HDPE content. For the in-process morphology controlled samples, the tensile properties depended not only on the phase morphology, but more importantly on the degree of orientation. One observed only a slight decrease of tensile property as the content of HDPE was less than 15 wt%, while an abrupt decrease when the content of HDPE was between 30 wt% and 50 wt%, probably due to the lowest degree of orientation in this composition range.
Co-reporter:Changyu Tang, Nanxi Chen, Qin Zhang, Ke Wang, Qiang Fu, Xinyuan Zhang
Polymer Degradation and Stability 2009 Volume 94(Issue 1) pp:124-131
Publication Date(Web):January 2009
DOI:10.1016/j.polymdegradstab.2008.09.008
In this work, the chitosan ternary nanocomposites with two-dimensional (2D) clay platelets and one-dimensional (1D) CNTs have been successfully prepared by a simple solution-intercalation/mixing method in acid media. It was found that the thermal degradation temperature of chitosan (at 50% weight loss) could be only improved in about 20–30 °C by adding 3 wt% either clay or CNTs, however, almost 80 °C increase of degradation temperature could be achieved by adding 2 wt% clay and 1 wt% CNTs together. Dynamic mechanical measurement demonstrated an obviously improved storage modulus for chitosan/clay–CNTs than that for the corresponding binary chitosan/clay or chitosan/CNT nanocomposites with the same total filler content (3 wt%). For the solvent vapor permeation properties, a largely improved benzene vapor barrier property was observed only in chitosan/clay–CNT ternary nanocomposites and depended on the ratio of clay to CNTs. XRD, SEM and TEM results showed that both clay and CNTs could be well dispersed in the ternary nanocomposites with the nanotubes located around the clay platelets. FTIR showed an improved interaction between the fillers and chitosan by using both clay and CNTs. A much enhanced solid-like behavior was observed in the ternary nanocomposites, compared with the corresponding binary nanocomposites with the same total filler content, as indicated by rheological measurement. The unique synergistic effect of two-dimensional (2D) clay platelets and one-dimensional (1D) CNTs on the property enhancement could be tentatively understood as due to a formation of much jammed filler network with 1D CNTs and 2D clay platelets combined together. Our work demonstrates a good example for the preparation of high performance polymer nanocomposites by using nanofillers with different dimensions together.
Co-reporter:Jing Cao;Ke Wang;Wen Cao;Qin Zhang;RongNi Du
Journal of Applied Polymer Science 2009 Volume 112( Issue 3) pp:1104-1113
Publication Date(Web):
DOI:10.1002/app.29540
Abstract
Molten polymers are usually exposed to varying levels of shear flow and temperature gradient in most processing operations. Many studies have revealed that the crystallization and morphology are significantly affected under shear. A so-called “skin-core” structure is usually formed in injection-molded semicrystalline polymers such as isotactic polypropylene (iPP) or polyethylene (PE). In addition, the presence of nucleating agent has great effect on the multilayered structure formed during injection molding. To further understand the morphological development in injection-molded products with nucleating agent, iPP with and without dibenzylidene sorbitol (DBS) were molded via both dynamic packing injection molding (DPIM) and conventional injection molding. The structure of these injection-molded bars was investigated layer by layer via SEM, DSC, and 2 days-WAXD. The results indicated that the addition of DBS had similar effect on the crystal size and its distribution as shear, although the later decreased the crystal size more obviously. The combination of shear and DBS lead to the formation of smaller spherulites with more uniform size distribution in the injection-molded bars of iPP. A high value of c-axis orientation degree in the whole range from the skin to the area near the core center was obtained in the samples molded via DPIM with or without DBS, while in samples obtained via conventional injection molding, the orientation degree decreased gradually from the skin to the core and the decreasing trend became more obvious as the concentration of DBS increased. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Co-reporter:Zhaojun Chen;Ping Luo
Polymers for Advanced Technologies 2009 Volume 20( Issue 12) pp:916-925
Publication Date(Web):
DOI:10.1002/pat.1336
Abstract
In order to prevent the properties, especially transparency, color and health security, of PET/clay nanocomposites from being deteriorated due to the thermal degradation of clay organo-modifer, we had directly modified sodium montmorillonite (Na+-MMT) with PET's monomer, bis (hydroxyethyl) terephthalate (BHET) which had a degradation temperature higher than 400°C, and successfully prepared the hybrids via in situ polymerization. Nanodispersion of clay and the intercalated morphology were determined, and compared with PET/Na+-MMT hybirds in which Na+-MMT was directly added without any treatment. Improved mechanical properties and Tg were observed for the prepared PET/ BHET-modified clay composites. More importantly, the film produced from the composites had the same transparency as that of pure PET even when 2 wt% of clay was added. Non-isothermal and isothermal crystallization experiments showed a very good neculation capability of the nano-dispersed clay, particularly at higher crystallization temperatures. Copyright © 2009 John Wiley & Sons, Ltd.
Co-reporter:Chengjuan Zhou;Ke Wang
Polymer International 2009 Volume 58( Issue 5) pp:538-544
Publication Date(Web):
DOI:10.1002/pi.2564
Abstract
BACKGROUND: Conventional rubber-like toughening modifiers are soft and amorphous, and when used to toughen polyamide 11 (PA11) they commonly induce a decrease in the tensile strength and modulus. In this study, crystallizable polyethylene (PE) derivatives, i.e. linear low-density polyethylene (LLDPE) and maleic anhydride-grafted polyethylene (PE-g-MA), were adopted to toughen PA11.
RESULTS: Compared to pure PA11, a highest improvement by a factor of eight in the impact toughness was achieved; also, the tensile strength and modulus could be maintained at a relatively high level. PE-g-MA acted as a compatibilizer for PA11 and LLDPE, bringing strong interfacial adherence, and especially a domain-in-domain morphology observed in PA11/PE-g-MA/LLDPE (70/10/20 by weight) blends. The observation that PA11 was toughened by the crystallizable PE derivatives is discussed in depth, based on the combined effect of surface crystallization of LLDPE on pre-formed PA11 crystallites and interfacial compatiblization between PA11 and PE-g-MA.
CONCLUSION: The crystallizable PE derivatives LLDPE and PE-g-MA were shown to be effective toughening modifiers for the proportions PA11/PE-g-MA/LLDPE 70/10/20 (by weight), which is considered to be an optimum composition: special domain-in-domain morphology was observed indicating a good dispersion of PE in the PA11 matrix and strong interfacial adherence between PE phase and PA11 phase. The reason why strength and modulus were maintained at a high level in the as-prepared blends was attributed to the existence of rigid crystalline domains in PE. Copyright © 2009 Society of Chemical Industry
Co-reporter:Xinlan Zhang, Bo Li, Ke Wang, Qin Zhang, Qiang Fu
Polymer 2009 50(19) pp: 4737-4744
Publication Date(Web):
DOI:10.1016/j.polymer.2009.08.004
Co-reporter:Ke Wang, Chenjuan Zhou, Changyu Tang, Qin Zhang, Rongni Du, Qiang Fu, Lin Li
Polymer 2009 50(2) pp: 696-706
Publication Date(Web):
DOI:10.1016/j.polymer.2008.11.019
Co-reporter:Run Su;Juanxia Su;Ke Wang;Daiqiang Chen;Changyue Yang
Journal of Polymer Science Part B: Polymer Physics 2009 Volume 47( Issue 3) pp:239-247
Publication Date(Web):
DOI:10.1002/polb.21633
Abstract
A novel change of phase behavior and properties of polyvinyl alcohol (PVA)/gelatin blends as a function of pH was reported. The PVA/gelatin blends were found to be completely miscible in acidic condition (pH < 4), partially miscible in basic condition (pH > 8), and immiscible in neutral condition (pH was ca. 6). As a result, the membranes cast from acidic condition showed the highest tensile strength and the lowest alcohol vapor permeation (AVP) rate; those obtained from neutral condition showed the lowest tensile strength and highest AVP rate; the properties of membranes cast from basic condition lay in between. The interaction between PVA and gelatin was investigated via Fourier transform infrared spectrum (FTIR), differential scanning calorimetry (DSC), and Zetasizer measurement. The novel pH-dependence of the blends was ascribed to the protonation of amino groups of gelatin in acidic condition, which resulted in a strong electrostatic attraction between NH of gelatin and OH of PVA. The partial miscibility in basic condition was due to the ionization of carboxyl groups of gelatin, which caused a stretching of gelatin via electrostatic repulsive force and a breakage of the H-bonding among the molecular chains, leading to a limited interaction between PVA and gelatin and forming a partially miscible blend. In neutral conditions, there were almost no charges (very limited protonation and ionization) at the weak polyampholyte gelatin, and the strong H-bonding among gelatin molecules themselves or PVA molecules themselves caused the phase separation between gelatin and PVA. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 239–247, 2009
Co-reporter:Nanying Ning, Feng Luo, Ke Wang, Rongni Du, Qin Zhang, Feng Chen, Qiang Fu
Polymer 2009 50(15) pp: 3851-3856
Publication Date(Web):
DOI:10.1016/j.polymer.2009.05.026
Co-reporter:Run Su, Ke Wang, Qin Zhang, Feng Chen and Qiang Fu, Wenfei Xu and Bing Na
The Journal of Physical Chemistry B 2009 Volume 113(Issue 21) pp:7423-7429
Publication Date(Web):May 6, 2009
DOI:10.1021/jp900625b
In this article, molecular orientation of crystalline and amorphous phases of both linear low-density polyethylene (LLDPE) and isotactic polypropylene (iPP) and epitaxy in the LLDPE/iPP blends prepared via dynamic packing injection molding have been investigated with the aid of polarized Fourier transform infrared (FTIR) spectroscopy and two-dimensional X-ray scattering (2D-WAXS). In LLDPE-rich blends, LLDPE was oriented along the shear flow direction, and iPP kept very low orientation. No epitaxial growth between LLDPE and iPP was observed. However, for the blends with LLDPE content less than 50 wt %, where iPP was the matrix and LLDPE formed the droplets, iPP was highly oriented along shear flow direction and LLDPE epitaxially grew onto iPP. The contact planes were (100)LLDPE and (010)iPP, and LLDPE molecules were about 50° apart from the shear direction. The epitaxy fraction in LLDPE/iPP blends could be tentatively calculated from the values of orientation function of the LLDPE crystalline a-axis (fa) and that of crystalline b-axis (fb). Both tensile strength and tensile modulus decreased with the increase of LLDPE composition, indicating they were composition dependent, though shear-induced orientation and epitaxial crystallization might play some role. The impact strength of the blend samples reached a plateau in the LLDPE composition range of 20−50%, due to the contribution of orientation and epitaxy.
Co-reporter:Feng Luo, Chengzhen Geng, Ke Wang, Hua Deng, Feng Chen, Qiang Fu and Bing Na
Macromolecules 2009 Volume 42(Issue 23) pp:9325-9331
Publication Date(Web):November 5, 2009
DOI:10.1021/ma901651f
It is widely believed that the trigonal β-form is favorable and effective for toughening isotactic polypropylene (iPP). Therefore, β-form content should be achieved as high as possible to realize excellent toughness in iPP. However, in this study, we demonstrate that the connection between crystallites might mainly determine the toughness of iPP instead of the β-crystal content. A new rare earth nucleator (WBG) was used to generate the rich β-crystalline structure in the compression-molded bars that were fabricated upon different molten temperatures (Tf). Interestingly, the increase in tensile elongation can be as large as 8 times for increased Tf. The polymorphic composition and overall crystallinity of β-nucleated iPP are almost independent of Tf. Nevertheless, the β-nucleated crystalline morphology has completely changed. Three types of β-crystalline morphology, namely, β-spherulite, β-transcrystalline entity, and “flower”-like agglomerate of β-crystallites, are sequentially obtained with increasing Tf. From the morphological point of view, the connection between the crystallites in “flower”-like agglomerate is significantly better than that for the crystallites generated under lower Tf. Therefore, it is concluded that the formation of β-nucleated iPP provides very good toughness only with sufficient connection between the crystallites. The result of this study clearly verifies the importance of crystal morphology on tuning the toughness of iPP. It provides important information for potential industrial applications.
Co-reporter:Jinghui Yang, Chaoyu Wang, Ke Wang, Qin Zhang, Feng Chen, Rongni Du and Qiang Fu
Macromolecules 2009 Volume 42(Issue 18) pp:7016-7023
Publication Date(Web):July 17, 2009
DOI:10.1021/ma901266u
The formation of a nanohybrid shish-kebab (NHSK) superstructure, in which fibrillous carbon nanotubes (CNTs) act as shish while polymer lamellae act as kebab, is a novel way to bond the polymer and CNTs together and was first observed in the solution crystallization of polyethylene in the presence of CNTs. In this work, a direct formation of nanohybrid shish-kebab in the injection molded bar of high-density polyethylene (HDPE)/multiwalled carbon nanotubes (MWCNTs) composite, has been achieved, via a so-called dynamic packing injection molding technology (DPIM), in which oscillatory shear field was imposed on the gradually cooled melt during the packing solidification stage. Interestingly, whatever the long axis of CNTs is perpendicular to or parallel to the shear flow direction, the lamellae of PE is always perpendicular to long axis of CNTs. The three-step mechanism, including (1) the disentanglement and orientation of both PE and CNTs, (2) PE folded-chain lamellae directly nucleated on CNTs surface and/or first formation of PE extended-chain shish directly on CNTs surface then followed by nucleation of folded-chain lamellae, and (3) the crystallization of PE kebabs on the PE decorated CNTs fibrils, was proposed to understand the formation of NHSK under effect of shear. Importantly, the NHSK structure can bring significant mechanical reinforcement in the HDPE/MWCNTs composite. For the oriented composites containing 5% MWCNTs, its tensile strength is increased by 150% and 270%, compared to the oriented pure HDPE and the isotropic composites containing 5% CNTs, respectively; meanwhile, its Young’s modulus is enhanced by 130% and 180%, compared to the oriented pure HDPE and the isotropic composites containing 5% CNTs, respectively. This work is the first to enlarge the theoretical value and application potential of NHSK structure in the crystallizable polymer/CNTs composite.
Co-reporter:Wenfei Xu, Ruihua Lv, Bing Na, Nana Tian, Zhujun Li and Qiang Fu
The Journal of Physical Chemistry B 2009 Volume 113(Issue 29) pp:9664-9668
Publication Date(Web):July 1, 2009
DOI:10.1021/jp901881y
A study on the mechanism for the degraded toughness in nylon 6/clay nanocomposite is explored in this Article. Such a nanocomposite exhibits lower specific essential work of fracture we and specific nonessential work of fracture βwp than its pure nylon 6 counterpart, as revealed by essential work of fracture (EWF) measurements. Furthermore, the molecular orientation in a small region (20 × 20 μm2) ahead of crack tip, obtained from micro-FTIR measurements for the first time, is found to be lower in the nanocomposite during crack initiation and propagation. The decreased molecular orientation, mostly resulted from severe microvoiding at crack tips, is responsible for the reduced specific essential work of fracture we. Meanwhile, the molecular orientation around crack tip also indicates that lower plastic deformation occurs in the plastic zone, which is well correlated with decreased specific nonessential work of fracture βwp in the nanocomposite.
Co-reporter:Mingming Ding, Jiehua Li, Xiaoting Fu, Jian Zhou, Hong Tan, Qun Gu and Qiang Fu
Biomacromolecules 2009 Volume 10(Issue 10) pp:
Publication Date(Web):September 28, 2009
DOI:10.1021/bm9006826
Novel cationic biodegradable multiblock poly(ε-caprolactone urethane)s that contain gemini quaternary ammonium side groups on the hard segments were developed. To obtain these polyurethanes, a new l-lysine-derivatized diamine containing gemini quaternary ammonium side groups (GA8) was first synthesized and characterized by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectra (NMR), mass spectrometry (MS), and high-resolution mass spectra (HRMS). Then a series of gemini poly(ε-caprolactone urethane)s were designed and prepared using l-lysine ethyl ester diisocyanate (LDI), poly(ε-caprolactone) (PCL) diols, 1,4-butandiol (BDO), and GA8 and were terminated by methoxyl-poly(ethylene glycol) (m-PEG). The obtained polyurethanes were fully characterized by 1H NMR, gel permeation chromatograph (GPC), differential scanning calorimetry (DSC), FTIR, and water contact angle (WCA) measurement. The gemini polyurethane shows a rapid rate of hydrolytic and enzymatic degradation, as demonstrated by weight loss and polarizing light microscopy (PLM) observations. In vitro cytotoxicity analysis suggests that both the polyurethanes and their degradation products do not show significant inhibition effect against fibroblasts. Our work provides a new way to synthesize nontoxic and amphiphilic multiblock polyurethanes with rapid degradation rate, and these new materials could be good candidates as biodegradable carriers for drug and gene delivery.
Co-reporter:S. Liang, H. Yang, K. Wang, Q. Zhang, R. Du, Q. Fu
Acta Materialia 2008 Volume 56(Issue 1) pp:50-59
Publication Date(Web):January 2008
DOI:10.1016/j.actamat.2007.09.008
Abstract
In this research, a linear low density polyethylene (LLDPE) was first melt blended with a series of high density polyethylenes (HDPE) with different molecular weights at a fixed ratio of LLDPE/HDPE = 90/10 (w/w). The prepared HDPE/LLDPE blends were then injection-molded into specimen bars through a dynamic packing injection molding (DPIM) technique, in which an oscillating shear field was imposed on the melt by two pistons that move reversibly with the same frequency during the packing stage. The crystal morphology, orientation and tensile properties were characterized by scanning electron microscopy, two-dimensional wide-angle X-ray scattering and Instron, respectively. Compared with conventional injection molding, DPIM caused an obvious increase in tensile strength in the injection-molded bars. Interestingly, LLDPE blended with low molecular weight HDPE (LMW-PE) was found to possess much higher tensile strength than that blended with high molecular weight HDPE (HMW-PE). Shish–kebab morphology was observed for all blends obtained, regardless of the molecular weight of the HDPE. However, thicker but shorter lamellae were observed for the LLDPE/LMW-PE blend, corresponding to a higher melting temperature; while thinner but longer lamellae were seen for the LLDPE/HMW-PE blend, corresponding to a lower melting temperature. Furthermore, the phase miscibility between HDPE and LLDPE was found to increase with increasing HDPE molecular weight, which would affect the sensitivity of molecular chains for response to external shear. The changed miscibility, together with the changed entanglement density in different HDPE was responsible for the change in tensile strength and unique crystal morphology of LLDPE induced by adding HDPE.
Co-reporter:Hong Yang, Bo Li, Ke Wang, Tongch en Sun, Xin Wang, Qin Zhang, Qiang Fu, Xia Dong, Charles C Han
European Polymer Journal 2008 Volume 44(Issue 1) pp:113-123
Publication Date(Web):January 2008
DOI:10.1016/j.eurpolymj.2007.10.028
In this article, the rheological properties of polypropylene (PP)/ethylene–propylene–diene terpolymer (EPDM)/silicon dioxide (SiO2) ternary composites were systematically investigated. Two kinds of nano-SiO2 particles (with hydrophobic (denoted as A-SiO2) or hydrophilic (denoted as B-SiO2)) as well as two processing methods (one-step or two-step) were first employed to prepare PP/EPDM/SiO2 ternary composites. Then the deep mixing and morphology evolution of polymer composite with mixing time were assessed by rheological method, on the focus of formation of filler-network, and compared with scanning electron microscopy (SEM) observations. Linear viscoelastic behavior was observed for PP/EPDM and PP/SiO2 binary system, showing no evidence of the formation of filler-network structure. However, a solid-like rheological behavior, which was attributed to the formation of the filler-network structure as confirmed by SEM observation, could be observed in some PP/EPDM/SiO2 ternary systems, depending on the SiO2 surface property, processing method and EPDM content. It seemed that SiO2 with hydrophilic surface was necessary for the formation of filler-network in PP/EPDM/SiO2 ternary system. Besides, two-step processing method made the solid-like behavior occurred at an earlier stage compared with that of a one-step processing method, also, the higher elastomer content facilitated the formation of the filler-network structure. The results were in good agreement with those reported in our previous publications [Yang H, Zhang Q, Guo M, Wang C, Du R, Fu Q. Polymer 2006;47:2106] [Yang H, Zhang X, Qu C, Li B, Zhang L, Zhang Q, et al. Polymer 2007;48:860].
Co-reporter:Juanxia Su;Qi Wang;Run Su;Ke Wang;Qin Zhang
Journal of Applied Polymer Science 2008 Volume 107( Issue 6) pp:4070-4075
Publication Date(Web):
DOI:10.1002/app.27552
Abstract
Polyvinyl alcohol (PVA)/gelatin composite fibers containing carbon nanotubes (CNTs) had been prepared by wet-spinning method. A remarkable increase of tensile strength of the PVA/gelatin fibers was achieved by adding small amount of CNT. The mechanism of reinforcement has been studied using a combination of differential scanning calorimetry (DSC), 2D wide-angle X-ray diffraction (2D-WAXD) and scanning electron microscopy (SEM). SEM showed a decreased gelatin domain size by adding CNTs, suggesting a possible compatibilization effect between PVA and gelatin. On the other hand, an increased crystallinity and degree of orientation of PVA/gelatin fibers has been observed by adding CNTs. Thus, the increased compatibilization, crystallinity and degree of orientation in PVA/gelatin/CNTs composite fibers should be the reasons for the observed increase of mechanical properties. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Co-reporter:Bobing He;Xiaoqing Zhang;Qin Zhang
Journal of Applied Polymer Science 2008 Volume 107( Issue 1) pp:94-101
Publication Date(Web):
DOI:10.1002/app.27000
Abstract
In this study, a noninvasive and nondestructive ultrasonic technique has been used to monitor the polymer injection-molding process in an attempt to establish a fundamental understanding of the processing/morphology/ultrasonic signal relationships. The ultrasonic technique not only can provide information on solidification affected by various temperatures and pressures but also can reflect the evolution of the crystal morphology and phase morphology of polymer blends. In addition, the periodic vibration of the dynamic-packing injection-molding process, in which the melt is forced to move repeatedly in a chamber by two pistons that move reversibly with the same frequency as the solidification progressively occurs from the mold wall to the molding core part, can also be monitored with the ultrasonic velocity and attenuation. Our results indicate that the ultrasonic technique is sensitive and promising for the real-time monitoring of the injection-molding process. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Co-reporter:Xiaoting Fu;Mingming Ding;Changyu Tang;Bo Li;Zeyong Zhao;Dai-Qiang Chen;Qin Zhang;Han Long;Touwen Tan
Journal of Applied Polymer Science 2008 Volume 109( Issue 6) pp:3725-3732
Publication Date(Web):
DOI:10.1002/app.28593
Abstract
The recycled polystyrene (rPS) was toughened with ethylene-octylene copolymer thermoplastic elastomer (POE) and high-density polyethylene (HDPE) with various melt flow index (MFI), compatibilized by styrene-butadiene-styrene copolymer (SBS) to enhance the toughness of rPS for use as TV backset. The rPS/POE binary blends exhibited an increased impact strength with 5–10 wt % POE content followed by a decrease with the POE content up to 20 wt %, which could be due to poor compatibility between POE and rPS. For rPS/POE/SBS ternary blends with 20 wt % of POE content, the impact strength increased dramatically and a sharp brittle-ductile transition was observed as the SBS content was around 3–5 wt %. Rheological study indicated a possible formation of network structure by adding of SBS, which could be a new mechanism for rPS toughening. In rPS/POE/HDPE/SBS (70/20/5/5) quaternary blends, a fibril-like structure was observed as the molecular weight of HDPE was higher (with lower MFI). The presence of HDPE fibers in the blends could not enhance the network structure, but could stop the crack propagation during fracture process, resulting in a further increase of the toughness. The prepared quaternary blend showed an impact strength of 9.3 kJ/m2 and a tensile strength of 25 MPa, which can be well used for TV backset to substitute HIPS because this system is economical and environmental friendly. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Co-reporter:Cheng Qu;Run Su;Qin Zhang;RongNi Du
Polymer International 2008 Volume 57( Issue 1) pp:139-148
Publication Date(Web):
DOI:10.1002/pi.2336
Abstract
Background: Poly(ethylene terephthalate) (PET)/polyamide-6 (PA-6) blends are promising for engineering and food-packaging applications. However, their poor toughness limits their use. In this study, an ethylene–acrylate–(maleic anhydride) terpolymer (E-AE-MA) was added to PET/PA-6 blends in order to improve the toughness.
Results: Izod impact tests indicated an excellent toughening effect of E-AE-MA. E-AE-MA particles were observed to be selectively dispersed at the interface between PET and PA-6 phases and in the domain of the PA-6 phase. Fourier transform infrared spectroscopy and differential scanning calorimetry results demonstrated that the formation of E-AE-MA layers around PA-6 particles cut off the interaction between PET and PA-6, resulting in an enlarged PA-6 phase domain.
Conclusion: Based on the experimental results, a core–shell microstructure, with PA-6 as a hard core and E-AE-MA as a soft shell, could be suggested. The formation of this core–shell microstructure, along with the increased PA-6 phase domain size, is the main toughening mechanism of E-AE-MA in PET/PA-6 blends. Copyright © 2007 Society of Chemical Industry
Co-reporter:Jinni Deng;Jing Cao;Jiehua Li;Hong Tan;Qin Zhang
Journal of Applied Polymer Science 2008 Volume 108( Issue 3) pp:2023-2028
Publication Date(Web):
DOI:10.1002/app.27625
Abstract
To improve the mechanical and surface properties of poly(etherurethane) (PEU), multi-walled carbon nanotubes (MWCNTs) were surface grafted by 3,3,4,4, 5,5,6,6,7,7,8,8,8-tridecafluoro-1-octanol (TDFOL) (MWCNT-TDFOL) and used as reinforcing agent for PEU. Fourier-transform infrared spectroscopy revealed the successful grafting of MWCNTs. PEU filled with MWCNT-TDFOL could be well dispersed in tetrahydrofuran solution, and tensile stress–strain results and dynamic mechanical analysis showed a remarkable increase in mechanical properties of PEU by adding a small amount of MWCNT-TDFOL. Contact angle testing displayed a limited improvement (just 9°) in the hydrophobicity of PEU surface by solution blending with MWCNT-TDFOL. However, a large improvement of surface hydrophobicity was observed by directly depositing MWCNT-TDFOL powder on PEU surface, and the water contact angle was increased from 80° to 138°. Our work demonstrated a new way for the modification of carbon nanotubes and for the property improvement of PEU. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Co-reporter:Jinghui Yang;Tao Xu;Ai Lu;Qin Zhang
Journal of Applied Polymer Science 2008 Volume 109( Issue 2) pp:720-726
Publication Date(Web):
DOI:10.1002/app.28098
Abstract
Poly(phenylene sulfide) (PPS)/multiwalled carbon nanotubes (MWNTs) conductive composites were prepared through the simple mixing of PPS granules with MWNT powder and subsequent compression. The electrical properties as a function of MWNT loading clearly showed a low percolation threshold of about 0.22 vol % and a high critical exponent value of 3.55 for composites prepared by this method. A comparison study with composites prepared via melt mixing was also carried out, where a random dispersion of MWNTs was achieved. There existed a striplike morphology of MWNTs in the PPS matrix and MWNTs were selectively located in strips caused by compression. The effects of temperature and pressure on the conductivity of the PPS/MWNT composites as prepared via simple mixing and compression are discussed. In addition, the conductivity also showed a dependence on the flow direction of the compression, with higher conductivity in the direction parallel to the flow direction than in the direction perpendicular to the flow direction. So the relationship of the processing and morphological properties was investigated in detail. The possible conductive mechanisms of conventional melt blending and preparation via sample mixing and compression are also discussed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Co-reporter:Li Cui;Jen-Taut Yeh;Ke Wang
Journal of Polymer Science Part B: Polymer Physics 2008 Volume 46( Issue 13) pp:1360-1368
Publication Date(Web):
DOI:10.1002/polb.21470
Abstract
An investigation of miscibility and isothermal crystallization behavior of Polyamide 6 (PA6)/Poly(vinyl alcohol) (PVA) blends was conducted. Fourier transform infrared spectra (FTIR) analysis indicated that the interactions between the carbonyl groups of PA6 and hydroxyl groups of PVA increase as the weight ratios of PA6 to PVA of PA6/PVA specimens increase. This interaction between PA6 and PVA leads to their miscibility in the amorphous region and even some extent effects on their crystal phase, respectively. Further isothermal crystallization behavior of PA6/PVA indicate that the miscibility of PVA in PA6 leading difficulty in crystallization of PA6. Several kinetics equations are employed to describe the effects of PVA on the crystallization properties of PA6 in PA6/PVA blends in detail. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1360–1368, 2008
Co-reporter:Nanying Ning, Feng Luo, Ke Wang, Qin Zhang, Feng Chen, Rongni Du, Chunyang An, Baofeng Pan and Qiang Fu
The Journal of Physical Chemistry B 2008 Volume 112(Issue 45) pp:14140-14148
Publication Date(Web):October 16, 2008
DOI:10.1021/jp8056515
In our previous work, a hybrid shish kebab structure, with polyethylene (PE) crystal lamellae periodically decorated on the surface of an inorganic whisker (SMCW) and aligned approximately perpendicular to the long axis of the whisker, has been observed in the injection molded bar of PE/SMCW composites. To investigate the effect of the molecular weight of the PE matrix on the formation of the hybrid shish kebab structure and the corresponding physical properties of HDPE/SMCW composites, in this work, three types of PE with different molecular weights were used to prepare the composites. They were first melt blended and then subjected to dynamic packing injection molding (DPIM), in which the prolonged shear was exerted on the melt during the solidification stage. An obvious hybrid shish kebab (HSK) structure, with PE crystal lamellae closely packed on the surface of the SMCW, was found in the samples with a low molecular weight PE (LMW-PE) matrix and a medium molecular weight PE (MMW-PE) matrix. However, in samples with a high molecular weight PE (HMW-PE) matrix, an incomplete HSK structure with PE crystal lamellae loosely decorated on the surface of the SMCW was observed. Furthermore, DSC results indicated that SMCW served as a good nucleating agent only for the composite with a LMW-PE matrix and the nucleation efficiency decreased with increasing PE molecular weight. Correspondingly, the tensile strength of the PE/SMCW composites was significantly improved by adding SMCW for the samples with a LMW-PE or MMW-PE matrix. Especially for samples with a LMW-PE matrix, the tensile strength was remarkably enhanced by the presence of only 1 wt % SMCW. For the composites with a HMW-PE matrix, the addition of SMCW had almost no reinforcing effect on the composites. The molecular weight dependence of the formation of HSK and property enhancement was discussed on the basis of the chain mobility and crystallization capability of the PE matrix.
Co-reporter:Jinni Deng, Xiaoqin Zhang, Ke Wang, Hao Zou, Qin Zhang, Qiang Fu
Journal of Membrane Science 2007 Volume 288(1–2) pp:261-267
Publication Date(Web):1 February 2007
DOI:10.1016/j.memsci.2006.11.033
A three-step surface treatment of multi-walled carbon nanotubes (MWCNTs) was used to enhance the mechanical and transport properties of poly(ether urethane) (PEU) film. The original MWCNTs were first carboxylated via a mixture of sulfuric and nitric acids to obtain MWCNT grafted to a –COOH group (MWCNT-COOH), then further hydroxylated via thionyl chloride and 1,6-hexanediol to obtain MWCNT grafted to 1,6-hexanediol (MWCNT-OH), and finally treated via isophorone diisocyanate (IPDI) to obtain MWCNT grafted to IPDI (MWCNT-IPDI), which had a similar structure to the hard segments of PEU. Fourier-transform infrared spectroscopy revealed that the functional group –IPDI was successfully grafted onto MWCNTs. Then the prepared MWCNT-IPDI was blended with PEU in a tetrahydrofuran solution to obtain the final transparent MWCNT-IPDI/PEU membranes. All the membranes were characterized by Instron, DMA, DSC and water vapor permeability (WVP). The results showed a remarkable enhancement of mechanical properties and glass-transition temperature of the hard-segments of PEU by adding only small amount of MWCNT-IPDI. For example, the tensile strength was increased from 26.2 MPa for pure PEU to 42 MPa for composites containing 0.3 wt% of MWCNT-IPDI, and the storage modulus was improved from 1500 MPa for pure PEU to 2350 MPa for composites containing 0.5 wt% of MWCNT-IPDI. Very interestingly, a largely improved WVP of PEU film has been achieved by mixing with MWCNT-IPDI. The WVP was increased from 646 g/m2 24 h for the pure PEU to 856 g/m2 24 h for the composites containing 0.3 wt% of MWCNT-IPDI, and to 1180 g/m2 24 h for the composites containing 0.8 wt% of MWCNT-IPDI.
Co-reporter:Ke Wang;Changyu Tang;Ping Zhao;Hong Yang;Qin Zhang;Rongni Du
Macromolecular Rapid Communications 2007 Volume 28(Issue 11) pp:1257-1264
Publication Date(Web):30 MAY 2007
DOI:10.1002/marc.200700069
A novel experimental technique to follow the crystallization processes of poly(propylene)/MWCNT composites that experience a steady shear deformation using dynamic melt rheometry is described. The effects of heterogeneous nucleation, temperature, and preshear on the crystallization behaviors were determined. A quantitative evaluation of crystallization kinetics difference between quiescent and preshear conditions could be achieved. By combining rheology with POM, we demonstrate that two different crystallization processes account for the shear-enhanced crystallization at low and high temperatures, respectively.
Co-reporter:Ke Wang, Si Liang, Ping Zhao, Cheng Qu, Hong Tan, Rongni Du, Qin Zhang, Qiang Fu
Acta Materialia 2007 Volume 55(Issue 9) pp:3143-3154
Publication Date(Web):May 2007
DOI:10.1016/j.actamat.2007.01.020
Abstract
Three isotactic polypropylene(iPP)/organoclay nanocomposites with changed basal resin polarity and molecular weight but fixed clay content (10 wt.%) were prepared through melt-blending. To correlate the rheological properties with the orientation behavior and tensile property in injection-molded bars, the shear response and disorientation kinetics of those molten composites were investigated through large-amplitude oscillatory shear measurements and stress relaxation experiments, respectively. Then, dynamic packing injection molding was carried out to exert oscillatory shear on the molten composites during the solidification stage, for preparation of composites with high-level orientation. The orientated structures of injection-molded bars were inspected through 2-D wide-angle X-ray scattering analysis. Our results indicated for the first time that the rheological behaviors, such as alignment induced by large-amplitude shear and stress relaxation, would be the reliable references for estimating the orientation capability of nanocomposites in practical injection-molded processing. The rheological response to shear and the disorientation kinetics play crucial roles in determining the orientation and tensile strength of molded composites.
Co-reporter:Tao Xu, Jinghui Yang, Jiwei Liu, Qiang Fu
Applied Surface Science 2007 Volume 253(Issue 22) pp:8945-8951
Publication Date(Web):15 September 2007
DOI:10.1016/j.apsusc.2007.05.028
Abstract
The surface modification of multi-walled carbon nanotubes (MWCNTs) by O2 plasma was carried out in this study. In order to achieve a relatively homogeneous treatment of MWCNTs powder, a rotating barrel fixed between the two discharge electrodes was used. The effect of plasma treatment parameters, such as power, time, and positions of samples (inside and outside the barrel), on the morphology and structure of MWCNTs surface was systematically analyzed by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The results showed that the direct discharge (outside the barrel) could result in not only a quick grafting of polar functional groups but also an easy damage of MWCNTs after longer time, particularly under intensive power. It was found that the surface of MWCNTs powder might be changed in three steps—expansion (loosed structure formed), peel off and oxidization with increasing of treatment time during the irradiation. In this way, a complete purification of MWCNTs powder could be finished within 30 min via plasma treatment. Our work suggested that plasma treatment could be a simple and nonpolluting method for a large scale purification of MWCNTs.
Co-reporter:Hao Zou;Run Su;Nanying Ning;Qin Zhang
Journal of Applied Polymer Science 2007 Volume 106(Issue 4) pp:2238-2250
Publication Date(Web):25 JUL 2007
DOI:10.1002/app.26880
By adding a small amount of clay into poly(p-phenylene sulfide) (PPS)/polyamide 66 blends, the morphology was found to change gradually from sea–island into cocontinuity and lamellar supramolecular structure, as increasing of clay content. Clay was selectively located in the PA66 phase, and the exfoliated clay layers formed an edge-contacted network. The change of morphology is not caused by the change of volume ratio and viscosity ratio but can be well explained by the dynamic interplay of phase separation between PPS and PA66 through preferential adsorption of PA66 onto the clay layers and through layer–layer repulsion. This provides a means of manipulating the phase morphology for the immiscible polymer blends. The mechanical and tribological properties of PPS/PA66 blends with different phase morphologies (different clay contents) were studied. Both tensile and impact strength of the blends were found obviously increased by the addition of clay. The antiwear property was greatly improved for the blends with cocontinuous phase form. Our work indicates that the phase-separating behavior of polymer blends contained interacting clay can be exploited to create a rich diversity of new structures and useful nanocomposites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Co-reporter:Nan-Ying Ning;Yong-Bin Zhu;Zhou-Kun He;Xiao-Qing Zhang
Journal of Applied Polymer Science 2007 Volume 105(Issue 5) pp:2737-2743
Publication Date(Web):14 MAY 2007
DOI:10.1002/app.26529
In this study, polyethylene (PE)/polystyrene (PS) polymeric gradient material with spatially gradient structure was prepared continuously by a new technique through coextrusion–gradient distribution–two-dimensional mixing with conventional polymeric material processing facilities. The processing line from coextrusion, gradient distribution to two-dimensional mixing was fulfilled by two extruders, gradient distribution unit, and two-dimensional mixing units, respectively. The gradient distribution unit and two-dimensional mixing units were designed separately in our group. The gradient variation of composition along the sample thickness direction was studied by differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). DSC results indicated that a gradient variation of the content of PE was formed along the sample thickness direction. SEM results showed the direct evolution of morphology of each specimen along the sample thickness direction. The experimental results demonstrated that the processing method with coextrusion–gradient distribution–two-dimensional mixing can be served as a new way to produce polymer blends with spatially gradient structure and worth to be further investigated. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Co-reporter:Jiang Li;Cheng Qu;Xiaoqing Zhang;Qin Zhang;RongNi Du
Journal of Applied Polymer Science 2007 Volume 105(Issue 4) pp:2252-2259
Publication Date(Web):26 APR 2007
DOI:10.1002/app.26225
In this article, the phase morphology and mechanical properties of polypropylene (PP)/ethylene–octane copolymer (POE) blends with fixed ratio (60/40) obtained via different processing conditions, including barrel temperature, injection speed, and mold temperature, have been investigated. SEM was carried out for detailed characterization of phase morphology from the skin to the core, layer by layer. It was interesting that for all the processing conditions no dispersed POE elastomer was observed in the skin layer but elongated POE particles with large size were observed in the subskin layer. From the transition zone to the core layer, an increased phase separation was observed, which could lead to a formation of cocontinuous morphology, depending on the processing condition used. Higher barrel temperature, lower mold temperature, and higher injection speed could result in a smaller size of POE phase. The tensile strength and impact strength were found not sensitive to barrel temperature and mold temperature but to the low injection speed, both tensile strength and impact strength had a higher value for specimen obtained via low injection speed. The formation of the skin-core morphology and the effect of processing conditions on the phase morphology were discussed based on crystallization kinetics of PP matrix, rheology, and shear induced phase mixing. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Co-reporter:Yan Xiao;Xiaoqing Zhang;Hong Tan;Ke Wang;Wen Cao;Rongni Du;Qin Zhang;Yan Xiao;Xiaoqing Zhang;Wen Cao;Ke Wang;Hong Tan;Qin Zhang;Rongni Du
Journal of Applied Polymer Science 2007 Volume 104(Issue 3) pp:1880-1886
Publication Date(Web):26 FEB 2007
DOI:10.1002/app.25852
In this article, polypropylene (PP)/multiwall carbon nanotubes (MWNTs) composites were prepared through dynamic packing injection molding, in which the oscillatory shear was exerted on the molten composite during packing and solidification stage of injection-molding. A simultaneous increase of tensile strength and impact strength has been achieved for PP/MWNTs composites containing only 0.6 wt % MWNTs. Particularly, the impact strength was found increased by almost 50% at such low MWNTs content. These improvements in properties were attributed to uniform dispersion and possible orientation of nanotube induced by shear stress. It was suggested that the dynamic packing injection molding could provide much strong shear force for better dispersion of MWNTs in PP matrix, on one hand, but breakdown the aspect ratio of MWNTs, on the other. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1880–1886, 2007
Co-reporter:Cheng Qu;Hong Yang;Wen Cao;Dong Liang;Dong Liang;Hong Yang;Wen Cao;Cheng Qu
Journal of Applied Polymer Science 2007 Volume 104(Issue 4) pp:2288-2296
Publication Date(Web):27 FEB 2007
DOI:10.1002/app.25690
A kind of hydrophilic nano-SiO2 was applied to poly(ethylene terephthalate)/polyamide-6 (PA-6) blends. Melt-blended composites were prepared at various component ratios and different nano-SiO2 levels. Mechanical, morphological, dynamic mechanical, and thermal tests were carried out to characterize the properties, morphology, and compatibilization of the composites. Increased impact strength, tensile strength, and modulus were observed by adding nano-SiO2 particles in the blends. The nano-SiO2 particles were found to be preferentially dispersed in PA-6, resulting in an increase of glass transition temperature and crystallization of PA-6. The mechanism of morphology and properties changes was discussed based on the selective dispersion of nano-SiO2 particles in the blends. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2288–2296, 2007
Co-reporter:Yang Wang;Jinni Deng;Ke Wang;Qin Zhang
Journal of Applied Polymer Science 2007 Volume 104(Issue 6) pp:3695-3701
Publication Date(Web):27 MAR 2007
DOI:10.1002/app.25677
So far, the reported content of multiwall carbon nanotubes (MWNTs) in polymer/MWNTs nanocomposites is usually above 0.1 wt %. In this article, we will report our work on the study of the morphology, crystallization, and mechanical properties of poly(ethylene terephthalate) (PET)/MWNTs nanocomposites prepared by in situ polymerization with very low content of MWNTs (from 0.01 to 0.2 wt %). Well-dispersed MWNTs with a big network throughout PET matrix were observed by SEM. The very small amount of MWNTs displayed a great nucleating effect on the PET crystallization. The crystallization temperature was improved for 6.4°C by using only 0.01 wt % MWNTs. The decreased chain mobility of PET by adding MWNTs was evident by the formation of imperfect or smaller/thinner crystallites with low melting temperature. An increased storage modulus was also achieved for the nanohybirds with MWNT content less than 0.05 wt %. Our result indicates that using very low content MWNTs (less than 0.1 wt %) is a simple way to achieve good dispersion, yet with remarkable enhancement for polymer/MWNTs modification. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3695–3701, 2007
Co-reporter:Hao Zou;Wei Xu;Qing Zhang
Journal of Applied Polymer Science 2006 Volume 99(Issue 4) pp:1724-1731
Publication Date(Web):6 DEC 2005
DOI:10.1002/app.22690
To explore the possibility of making poly(p-phenylene sulfide) (PPS) nanocomposites via melt intercalation and improving the mechanical properties of PPS, in this study we first modified clay (montmorillonite) with alkylammonium salt by cation exchange and then mixed the modified clay together with the PPS matrix by twin-screw extrusion. Because the PPS/clay composites were made at a high temperature (300°C), thermogravimetric analysis experiments were carried out first to check the thermal stability of the alkylammonium salt treated clay and the obtained composites. Possible degradation of the alkylammonium salt during processing caused a decrease in the interlayer spacing of the clay. Scanning electron microscopy, transmission electron microscopy, and X-ray diffraction were used to investigate the dispersion of the clay sheet in the matrix. The clay layers were homogeneously dispersed in the PPS matrix with a nanometer scale, and an exfoliated structure was achieved at a low load of clay. The alkylammonium salt modifier enhanced the interaction between the PPS and clay on the one hand, but on the other hand, it also acted as a plasticizer and caused decreases in the glass-transition temperature and tensile properties. More work is needed to find a modifier and processing conditions by which the modifier can help the dispersion of clay and also be completely degraded after the formation of an exfoliated structure. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1724–1731, 2006
Co-reporter:Bing Na;Min Guo;Jinghui Yang;Hong Tan;Qin Zhang
Polymer International 2006 Volume 55(Issue 4) pp:
Publication Date(Web):7 MAR 2006
DOI:10.1002/pi.1996
Using polarized optical microscopy (POM) equipped with a hot stage, morphological investigations of an isotactic polypropylene (iPP) matrix, induced by a homogeneous iPP fibre and heterogeneous pure/modified nylon 6 fibres, were carried out. With respect to transcrystallization related to heterogeneous nucleation on the surface of the fibre, the nucleation mode was found to be different for iPP fibres and nylon 6 fibres. An iPP fibre can serve as a macroscopic linear nucleus, similarly to the shish-type structure formed in stress-induced crystallization, to induce kebab-like growth of lamellae, whereas numerous closely packed spherulites along nylon 6 fibres resulted in macroscopic transverse growth to form a transcrystallite owing to the limitation along the fibre axis. The difference in nature between these two transcrystallites can be further demonstrated by their optical characters related to the lamellar arrangement inside the transcrystallite. As for homogeneous iPP composites, the formation of transcrystallites results from lattice matching, in consideration of the same chemical structure and lattice parameters between fibre and matrix. The incorporation of calcium chloride into a nylon 6 fibre—to destroy its crystal structure—confirmed the role of lattice matching between nylon 6 fibre and iPP matrix. The addition of atactic polypropylene (aPP) in order to enhance the nucleation ability of the iPP matrix also greatly weakened transcrystallization. Our work demonstrates that transcrystallization is just a matter of competition between interface nucleation and bulk nucleation, namely, if interface nucleation is faster than bulk nucleation, transcrystallization will develop. If not, it will be suppressed. Copyright © 2006 Society of Chemical Industry
Co-reporter:Hong Tan;Taolei Sun;Jiehua Li;Min Guo;Xingyi Xie;Yinping Zhong;Lei Jiang
Macromolecular Rapid Communications 2005 Volume 26(Issue 17) pp:
Publication Date(Web):22 AUG 2005
DOI:10.1002/marc.200500326
Summary: In this article, we designed and synthesized novel segmented poly(carbonate urethane)s containing both hydrophobic fluorinated alkyl group and hydrophilic phosphatidylcholine polar head groups on the side chain. The contact angle measurement, XPS, together with ATR-IR investigation indicated a reversible overturn of the phosphatidylcholine groups with the movement of the hydrophobic fluorinated alkyl groups when the samples were treated in dry air or water. The change in environment from air to water induced a reorganization of the surface in order to minimize the interfacial free energy, resulting in a macroscopic change of surface wettability. The good environmental responsiveness of such biomembrane-mimicking films may find successful applications as biomaterials.
Co-reporter:Ya Peng;Qin Zhang;Rongni Du
Journal of Applied Polymer Science 2005 Volume 96(Issue 5) pp:1816-1823
Publication Date(Web):30 MAR 2005
DOI:10.1002/app.20702
In this study, blends of metallocene short-chain branched polyethylene (SCBPE) with low-density polyethylene (LDPE), high-density polyethylene (HDPE), polystyrene (PS), ethylene–propylene–diene monomer (EPDM), and isotactic polypropylene (iPP) were prepared in weight proportions of 80 and 20, respectively. The crystallization behaviors of these blends were studied with polarized light microscopy (PLM) and differential scanning calorimetry. PLM showed that SCBPE/LDPE, SCBPE/HDPE, and SCBPE/EPDM formed band spherulites whose band widths and sizes were both smaller than that of pure SCBPE. No spherulites were observed, but tiny crystallites were observed in the completely immiscible SCBPE/PS, and the crystallites in SCBPE/iPP became smaller; only irregular spherulites were seen. The crystallization kinetics and mechanical properties of SCBPE were greatly affected by the second polyolefin but in different way, depending on the phase behavior and the moduli of the second components. SCBPE may be phase-miscible in the melt with LDPE, HDPE, and EPDM but phase-separated during crystallization. A big change in the crystal morphology and crystallization kinetics existed in the SCBPE/iPP blend. The mechanical properties of the blends were also researched with dynamic mechanical analysis (DMA). DMA results showed that the tensile modulus of the blends had nothing to do with the phase behavior but only depended on the modulus of the second component. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1816–1823;2005
Co-reporter:Si Liang;Qin Zhang;Rongni Du;Ke Wang;Si Liang;Ke Wang;Qin Zhang;Rongni Du
Journal of Polymer Science Part B: Polymer Physics 2005 Volume 43(Issue 15) pp:2005-2012
Publication Date(Web):24 JUN 2005
DOI:10.1002/polb.20487
A well-exfoliated morphology is usually observed for polar polymer/clay nanocomposites via dynamic melt processing techniques, whereas only an intercalated or a partially intercalated/partially exfoliated morphology is often obtained for nonpolar polymer/clay nanocomposites, even though some polar compatibilzer is used. In this study, an accelerated exfoliation effect was observed for the first time in iPP/organoclay nanocomposites prepared through so-called dynamic packing injection molding, in which the specimen is forced to move repeatedly in a chamber by two pistons that move reversibly with the same frequency as the solidification progressively occurs from the mold wall to the molding core part. The disordered level and exfoliated degree of clay was found to dramatically increase from the skin to the core of the prepared samples and eventually the WAXD reflections of interlayer d-spacing diminished in the core. The changed degree of exfoliation was also proved directly by TEM observation. The prolongation of processing time, the gradual growth of solidification front, the increased melts viscosity, and the shear amplification effect were considered to explain the higher degree of exfoliation in the center zone of mold chamber. Our result suggests that a critical shear force may be needed to break down clay into exfoliated structure. This can be also well used to explain at least partially the intercalated morphology, which is commonly observed for nonpolar polymer/clay nanocomposites via conventional processing. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2005–2012, 2005
Co-reporter:Qin Zhang;Min Yu
Polymer International 2004 Volume 53(Issue 12) pp:
Publication Date(Web):12 OCT 2004
DOI:10.1002/pi.1581
Polyamide-11 (PA11)/clay nanocomposites were prepared by in situ intercalative polymerization. The crystal morphology and crystallization kinetics of these nanocomposites were investigated via polarized light microscopy (PLM), small-angle laser scattering (SALS) and differential scanning calorimetry (DSC). PA-11 can crystallize into well-formed spherulites, while only very tiny crystallites were observed by PLM and SALS for the nanocomposites. Both isothermal and non-isothermal crystallization methods were employed to investigate the crystallization kinetics by DSC. Both techniques showed an increased crystallization rate with the addition of clay. However, the Avrami exponent decreased with the addition of clay in isothermal crystallization but showed a wide range of values depending on the cooling rate in the non-isothermal crystallization. The changes in crystal morphology and crystallization kinetics can be understood as being due to the ‘supernucleating’ effect of the nanodispersed clay layers. Copyright © 2004 Society of Chemical Industry
Co-reporter:Nanying Ning, Sirui Fu, Wei Zhang, Feng Chen, Ke Wang, Hua Deng, Qin Zhang, Qiang Fu
Progress in Polymer Science (October 2012) Volume 37(Issue 10) pp:1425-1455
Publication Date(Web):1 October 2012
DOI:10.1016/j.progpolymsci.2011.12.005
Polymer/filler composites have been widely used in various areas. One of the keys to achieve the high performance of these composites is good interfacial interaction between polymer matrix and filler. As a relatively new approach, the possibility to enhance polymer/filler interfacial interaction via crystallization of polymer on the surface of fillers, i.e., interfacial crystallization, is summarized and discussed in this paper. Interfacial crystallization has attracted tremendous interest in the past several decades, and some unique hybrid crystalline structures have been observed, including hybrid shish–kebab and hybrid shish–calabash structures in which the filler served as the shish and crystalline polymer as the kebab/calabash. Thus, the manipulation of the interfacial crystallization architecture offers a potential highly effective route to achieve strong polymer/filler interaction. This review is based on the latest development of interfacial crystallization in polymer/filler composites and will be organized as follows. The structural/morphological features of various interfacial crystallization fashions are described first. Subsequently, various influences on the final structure/morphology of hybrid crystallization and the nucleation and/or growth mechanisms of crystallization behaviors at polymer/filler interface are reviewed. Then recent studies on interfacial crystallization induced interfacial enhancement ascertained by different research methodologies are addressed, including a comparative analysis to highlight the positive role of interfacial crystallization on the resultant mechanical reinforcement. Finally, a conclusion, including future perspectives, is presented.
Co-reporter:Yi Zhou, Yan Zhou, Hua Deng, Qiang Fu
Composites Part A: Applied Science and Manufacturing (May 2017) Volume 96() pp:
Publication Date(Web):May 2017
DOI:10.1016/j.compositesa.2017.02.002
The morphology of conductive network and their interfacial interaction with polymer matrix is thought as the key influential issues for the pressure/strain sensing behavior of conductive polymer composites (CPCs). The surface characteristics and size of these secondary insulating fillers should significantly influence the pressure/strain sensing behavior due to its influence on the morphology of conductive network and interfacial interaction between filler and polymer matrix. Herein, insulating SiO2 with different size and surface characteristics are incorporated into carbon black (CB)/silicon rubber (SR) composites to modify its piezo-resistive behavior. The conductivity of CB/SiO2/SR composites with nanoscale and hydrophobic SiO2 changes by several orders of magnitude, with more linear proportional to applied pressure and better stability under long term cyclic pressure due to better dispersion and stronger interfacial interaction. Through such simple method, high-performance piezo-resistive sensors could be fabricated with reversible piezo-resistivity, large pressure application (pressure below 2500 kPa) and tunable piezo-resistive sensitivity.
Co-reporter:Meng Ma, Jing Wang, Feng Chen, Qiang Fu
European Polymer Journal (March 2017) Volume 88() pp:
Publication Date(Web):March 2017
DOI:10.1016/j.eurpolymj.2017.01.018
•The coupling and competition of phase separation and crystallization is studied.•Transition of lamellae orientation from edge-on to flat-on is achieved with increasing Mw of PS.•Transition from nucleation-controlled faceted habits to diffusion-limited dendrites is found.•A simple method is proposed to control the crystal structure of thin polymer films.The morphology and lamellar orientations in the thin blend films (∼30 nm) of poly(ε-caprolactone) (PCL) and different molar mass of polystyrene(PS) were investigated by atomic force microscopy (AFM). The influence of PS molar mass on the PCL crystal structures was studied. The results show that both fibrous edge-on and flat-on microcrystal can be obtained when low molar mass PS (LPS with Mw = 3.7k and 7.5k) is added into the thin PCL films, while only flat-on crystal is constructed for the films blending with high molar mass PS (HPS with Mw = 15.5k and 54k and 106k). The different crystal morphology formation is explained based on the competition between phase separation and crystallization. For the LPS/PCL blend films, it is the homogeneous nucleation crystallization of PCL at the films surface that leads to the formation of fibrous edge-on together with several isolated and faceted flat-on crystals. While for the HPS/PCL blend films, it is the first vertical phase separation followed by the heterogeneous nucleation of PCL at polymer/substrate interface process that results in the morphology of flat-on PCL crystal decorated by PS domain island or dewetting hollows on the top.Different molar mass of PS is introduced into thin PCL films to study the effects of PS molar mass on the crystal morphology and lamellar orientation of PCL on mica substrate. Both fibrous edge-on and flat-on microcrystal morphology can be obtained for the LPS/PCL blend films, while only flat-on crystal structure is constructed in the blend films of HPS/PCL.Figure optionsDownload full-size imageDownload high-quality image (126 K)Download as PowerPoint slide
Co-reporter:Hua Deng, Lin Lin, Mizhi Ji, Shuangmei Zhang, Mingbo Yang, Qiang Fu
Progress in Polymer Science (April 2014) Volume 39(Issue 4) pp:627-655
Publication Date(Web):1 April 2014
DOI:10.1016/j.progpolymsci.2013.07.007
Since the emergence of large aspect ratio and multifunctional conductive fillers, such as carbon nanotubes, graphene nanoplates, etc., conductive polymer composites (CPCs) have attracted increasing attention. Although the morphological control of conductive networks in CPCs has been extensively investigated as an important issue for the preparation of high performance CPCs, recent extensive progress has not been systematically addressed in any review. It has been observed that the morphological control of conductive networks during the preparation of CPCs has crucial influence on the electrical properties of these composites. Several methods have been shown to be able to control the network structure, and thus, tune the electrical properties of CPCs, including the use of shear, polymer blends, thermal annealing, mixed filler, latex particle etc. Moreover, many novel and exciting applications have been extensively investigated for CPCs, such as stretchable conductor, electroactive sensors, shape memory materials and thermoelectric materials, etc. Therefore, the morphological control of conductive network in CPCs is reviewed here. Issues regarding morphology characterization methods, morphological control methods, resulted network morphology and electrical properties are discussed. Furthermore, the use of CPCs as electroactive multifunctional materials is also reviewed.
Co-reporter:Xiaodong Qi, Hao Xiu, Yuan Wei, Yan Zhou, Yilan Guo, Rui Huang, Hongwei Bai, Qiang Fu
Composites Science and Technology (8 February 2017) Volume 139() pp:8-16
Publication Date(Web):8 February 2017
DOI:10.1016/j.compscitech.2016.12.007
Co-reporter:Tianyu Liu, Rui Huang, Xiaodong Qi, Peng Dong, Qiang Fu
Polymer (7 April 2017) Volume 114() pp:28-35
Publication Date(Web):7 April 2017
DOI:10.1016/j.polymer.2017.02.077
Co-reporter:Huili Liu, Dongyu Bai, Hongwei Bai, Qin Zhang and Qiang Fu
Journal of Materials Chemistry A 2015 - vol. 3(Issue 26) pp:NaN13847-13847
Publication Date(Web):2015/05/25
DOI:10.1039/C5TA02017D
In recent years, there has been growing interest in developing poly(L-lactide)/carbon nanotube (PLLA/CNT) nanocomposites due to their considerable application value and potential. Unfortunately, the fabrication of high-performance PLLA/CNT nanocomposites still faces several obstacles mainly related to the low crystallization rate of the PLLA matrix as well as poor interfacial adhesion between the matrix and CNTs. In this work, we demonstrate a facile and promising route to simultaneously address these limitations by compositing PLLA with poly(D-lactide) grafted multi-walled carbon nanotubes (MWCNTs-g-PDLA) which can be synthesized via in situ ring-opening polymerization of D-lactide on the MWCNT surface. During melt-mixing of PLLA with the as-prepared MWCNTs-g-PDLA, the grafted PDLA chains and PLLA matrix chains tend to arrange side by side at the composite interface and finally co-crystallize into stereocomplex (SC) crystallites capable of serving as not only a highly active nucleating agent to dramatically accelerate matrix crystallization but also an effective interfacial enhancer to greatly improve the interfacial stress transfer efficiency. As a result, PLLA/MWCNTs-g-PDLA nanocomposites exhibit a much higher matrix crystallization rate and mechanical strength as compared to PLLA/MWCNTs-g-PLLA counterparts, where only limited physical entanglement between grafted and matrix chains forms across the interface. Moreover, both the crystallization rate and mechanical strength can be readily manipulated by tailoring the length of the grafted PDLA chains. This work could provide access to design advanced PLLA-based nanocomposites with fast matrix crystallization ability and outstanding mechanical properties via constructing multifunctional SC crystal structures at the interface.
Co-reporter:Dongsheng Tan, Zhen Li, Xuelin Yao, Chunlan Xiang, Hong Tan and Qiang Fu
Journal of Materials Chemistry A 2014 - vol. 2(Issue 10) pp:NaN1353-1353
Publication Date(Web):2013/12/03
DOI:10.1039/C3TB21473G
To study the influence of fluorinated surfaces and biomimetic surfaces on the improvement of the blood compatibility of polymers, three monomers containing a fluorinated tail and/or phosphorylcholine groups were designed and synthesized, and were then introduced into polyurethanes based on 4,4′-diphenylmethane diisocyanate (MDI), poly(tetramethylene glycol) (PTMG) and 1,4-butanediol (BDO) via end-capping. The bulk and surface characterization of the polyurethanes was carried out by dynamic mechanical analysis (DMA), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopic analysis (XPS), atomic force microscope (AFM), and water contact angle measurements. The results indicate that the fluorocarbon chains can drive the phosphorylcholine groups to aggregate at the surface of polyurethane, and the two components show spontaneous arrangement to adapt to the environment when in contact with water. The preliminary evaluation of hemocompatibility was carried out via fibrinogen adsorption and platelet adhesion. The fluorocarbon chains and phosphorylcholine groups showed a synergistic effect on the improvement of hemocompatibility.
Co-reporter:Lingyan Duan, Sirui Fu, Hua Deng, Qin Zhang, Ke Wang, Feng Chen and Qiang Fu
Journal of Materials Chemistry A 2014 - vol. 2(Issue 40) pp:NaN17098-17098
Publication Date(Web):2014/08/15
DOI:10.1039/C4TA03645J
The use of conductive polymer composites (CPCs) for strain sensing applications has attracted intense interest lately. The stability and sensitivity of resistivity–strain behaviour are thought to be important issues, but systematic investigations are missing. Herein, the resistivity–strain behavior in terms of stability and sensitivity of CPCs based on poly(styrene-butadiene-styrene) (SBS) containing multiwalled carbon nanotubes (MWCNTs) are studied. It is demonstrated that the preparation method has an important influence on the resistivity–strain behavior of these CPCs. Under linear uniaxial strain, the sensitivity increases with decreasing filler content for both composites, showing higher strain sensitivity near the percolation threshold. Moreover, a higher and wider range of sensitivities is obtained for SBS/MWCNT composites from melt mixing. Under dynamic strain, resistivity downward drifting and shoulder peaks are shown for composites from melt mixing, while linear relationships and reversible resistivity in every cycle are observed for composites from solution mixing, showing good electromechanical consistency, stability and durability. From the TEM, rheology, SEM, SAXS, Raman microscopy and analytical modeling studies, the difference in morphology is thought to be responsible for such resistivity–strain behavior. As more disordered and less densely packed conductive networks in melt-mixed CPCs are more easily destroyed under strain, evenly distributed and densely packed networks in solution mixed CPCs are more stable during cyclic stretching. Finally, human knee motions have been detected using these CPCs, demonstrating a potential application of these CPCs as movement sensors.
Co-reporter:Wenjing Ji, Junyi Ji, Xinghong Cui, Jianjun Chen, Daijun Liu, Hua Deng and Qiang Fu
Chemical Communications 2015 - vol. 51(Issue 36) pp:NaN7672-7672
Publication Date(Web):2015/03/24
DOI:10.1039/C5CC00965K
Polypyrrole (PPy) encapsulated 3D flower-like NiO was prepared to investigate the role of PPy coating for high-performance electrodes. NiO@PPy showed a better electrochemical performance than pure NiO, and a “trade-off effect” between electrical conductivity and ion diffusion resistance was observed with different PPy coating thickness.
Co-reporter:Jian Gao, Feng Chen, Ke Wang, Hua Deng, Qin Zhang, Hongwei Bai and Qiang Fu
Journal of Materials Chemistry A 2011 - vol. 21(Issue 44) pp:NaN17630-17630
Publication Date(Web):2011/10/17
DOI:10.1039/C1JM14300J
We show an order of magnitude increase in yield strength and Young's modulus of poly(propylene carbonate) (PPC) by adding a small amount of graphene oxide (GO) nanosheets, accompanied by a dramatic increase of glass transition temperature (Tg). The reinforced tensile properties are comparable to those of conventional polyethylene. This work opens the door to replace conventional polyethylene by PPC.
Co-reporter:Xiaodong Qi, Xuelin Yao, Sha Deng, Tiannan Zhou and Qiang Fu
Journal of Materials Chemistry A 2014 - vol. 2(Issue 7) pp:NaN2249-2249
Publication Date(Web):2013/11/29
DOI:10.1039/C3TA14340F
A novel water-induced shape memory polymer based on polyvinyl alcohol (PVA) was prepared by introducing graphene oxide (GO). Due to the strong hydrogen bonding interaction between PVA and GO, some additional physically cross-linked points could be formed in PVA, which largely improved shape memory properties of PVA. Solvent-induced shape memory behavior was observed by immersing PVA/GO nanocomposites in water. The water-induced shape recovery was due to the decrease of glass transition temperature and storage modulus. This could be explained by the swelling plasticizing effect of water on PVA, as indicated by the obvious expansion in volume of PVA. On the other hand, the weakened hydrogen bonding between PVA and GO was also observed after immersing the PVA/GO nanocomposites in water. Thus both the plasticizing effect and the competitive hydrogen bonding were the two main reasons for the shape recovery of PVA/GO nanocomposites. This study provides a framework for developing new shape memory polymers (SMPs) and for better understanding the shape recovery mechanism in solvent-induced SMPs.
Co-reporter:Kai Liu, Li Chen, Yao Chen, Jieli Wu, Weiyi Zhang, Feng Chen and Qiang Fu
Journal of Materials Chemistry A 2011 - vol. 21(Issue 24) pp:NaN8617-8617
Publication Date(Web):2011/05/11
DOI:10.1039/C1JM10717H
The introduction of graphene into a polymer matrix can markedly improve its mechanical properties and electrical conductivity. We report herein a novel strategy to fabricate polyester/reduced graphene oxide composites via simultaneous dispersion and thermo-reduction of graphene oxide (GO) during in situ melt polycondensation. The pristine graphite was first oxidized using a strong oxidant acid to prepare GO, and then GO sheets were dispersed into ethylene glycol (EG), where a homogeneous dispersion of GO in EG was obtained with ultrasonication. Finally polyester/reduced graphene oxide composites were prepared via in situpolymerization of terephthalic acid (PTA) and ethylene glycol containing well dispersed GO. Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and sedimentation experiments have been used to characterize the prepared composites. It is demonstrated that poly(ethylene terephthalate) (PET) chains may have been sucessfully grafted onto GO sheets during polymerization, accompanied by the thermo-reduction from GO to graphene. The TGA and XPS results showed that the content of grafted PET polymer was about to 60–80%, which indicates a homogeneous dispersion of GO sheets in the PET matrix, as demonstrated by SEM. Furthermore, a significant improvement in tensile strength and elongation at break of PET has been achieved. Therefore, our work provides a new way for the preparation of polyester/reduced graphene oxide composites and functionalization of graphene.
Co-reporter:Xiaodong Qi, Guanghui Yang, Mengfan Jing, Qiang Fu and Fang-Chyou Chiu
Journal of Materials Chemistry A 2014 - vol. 2(Issue 47) pp:NaN20401-20401
Publication Date(Web):2014/10/16
DOI:10.1039/C4TA04954C
A novel, biologically friendly polymer with shape memory and self-healing properties based on poly(propylene carbonate) (PPC)/microfibrillated cellulose (MFC) was prepared. MFC was first modified by a one-step mechanical–chemical approach involving ball milling and esterification reaction. In this way, MFC could be incorporated into PPC at up to 20 wt% with excellent dispersion. The formation of the “MFC network” structure in the PPC matrix was verified by scanning electron microscopy, and the strong interfacial interaction between PPC and MFC was confirmed by X-ray photoelectron spectroscopy. The incorporation of MFC not only significantly enhanced the mechanical strength and thermal stability of the polymer, but also acted as a physical cross-linker that could improve the shape memory property of PPC at specific contents (5–10 wt%). More importantly, due to the shape memory effect and the reinforcement of MFC fibres, the polymer composites also showed enhanced scratch resistance and scratch self-healing behaviour. Our work provides an approach to tune the shape memory behaviours of polymer composites and may contribute to the application of PPC in the field of smart materials.
Co-reporter:Hua Deng, Mizhi Ji, Dongxue Yan, Sirui Fu, Lingyan Duan, Mengwei Zhang and Qiang Fu
Journal of Materials Chemistry A 2014 - vol. 2(Issue 26) pp:NaN10058-10058
Publication Date(Web):2014/04/07
DOI:10.1039/C4TA01073F
The resistivity–strain behavior of conductive polymer composites (CPCs) has gained intense interest due to its importance for various applications. The resistivity of CPCs often increases substantially and linearly under strain. To achieve constant resistivity under strain, a large filler content and special network configuration are often required. And a tunable step-wise resistivity–strain behavior has yet to be reported. Herein, a new method combining polymer blends and pre-stretching is introduced to modify the resistivity–strain behavior of CPCs based on thermoplastic polyurethane (TPU)/polyolefin elastomer (POE) with multi-walled carbon nanotubes (MWCNTs) selectively incorporated in the TPU phase. Depending on the compositions of blends and the intensity of pre-stretching, various interesting resistivity–strain behaviors have been achieved. The resistivity can be either linearly increasing or constant. Interestingly, two-stepwise resistivity–strain behavior has been achieved, with first an increase then a constant value. To understand this unique phenomenon, the phase morphology and conductive network structure are systematically characterized. It is observed that the orientation of MWCNTs is strongly correlated with overall resistivity. Finally, a mechanism involving fibrillization and “slippage” between conductive phases is proposed to explain the resistivity–strain dependency. This study provides guidelines for the preparation of high performance strain sensors as well as stretchable conductors.
Co-reporter:Weixing Yang, Zedong Zhao, Kai Wu, Rui Huang, Tianyu Liu, Hong Jiang, Feng Chen and Qiang Fu
Journal of Materials Chemistry A 2017 - vol. 5(Issue 15) pp:NaN3756-3756
Publication Date(Web):2017/03/14
DOI:10.1039/C7TC00400A
With the extensive use of portable and wearable electronic devices, ultrathin electromagnetic interference (EMI) shielding materials with excellent thermal management are increasingly desirable. In this study, ultrathin and highly aligned reduced graphene oxide (RGO)/cellulose nanofiber (CNF) composite films with excellent EMI shielding performance and strong anisotropy of thermal conductivity were fabricated by vacuum-assisted filtration followed by hydroiodic acid (HI) reduction. The obtained 50 wt% RGO/CNF composite films, which are only ≈23 μm in thickness, possess the remarkable electrical conductivity of ≈4057.3 S m−1 and outstanding EMI shielding effectiveness (SE) of ≈26.2 dB owning to the uniform dispersion and self-alignment into the layered structure of RGO. In addition, the RGO/CNF composite films with 50 wt% RGO loadings possess high in-plane thermal conductivity (K ≈ 7.3 W m−1 K−1) and, unexpectedly, very low cross-plane thermal conductivity (K⊥ ≈ 0.13 W m−1 K−1), resulting in strong anisotropy of the thermal conductivity (K/K⊥ ≈ 56). Thus, these ultrathin RGO/CNF composite films have great application potential as effective lightweight shielding materials against electromagnetic microwaves and heat, especially in flexible portable electronic devices and wearable devices.
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