Co-reporter:Ming TianXiuchun Zhen, Zhifei Wang, Hua Zou, Liqun Zhang, Nanying Ning
ACS Applied Materials & Interfaces 2017 Volume 9(Issue 7) pp:
Publication Date(Web):January 24, 2017
DOI:10.1021/acsami.6b16308
Adaptive mechanical behaviors in nature have inspired the development of synthetic adaptive composites, with those responsive to water particularly relevant for biomedical applications. Polymer nanocomposites containing cellulose nanocrystals (CNCs) are prime examples of water-responsive mechanically adaptive materials. Although CNCs are biobased, the matrixes of these composites are exclusively petroleum-based synthetic elastomers, in sharp contrast to their biological counterparts. In this work, we attempted to probe the possibility of using bioderived rubber(s) as the matrix to fabricate CNC-nanocomposite with water-responsive adaptive mechanical behaviors. Specifically, natural rubber (NR) and epoxidized natural rubber (ENR) were used as the composite matrixes. Our results show that the water-responsive sensitivity and reversibility of ENR composites is much more drastic than that of NR composites. This is attributed to the strong CNC–polymer interaction (hydrogen bonding) for ENR, which leads to better filler dispersion and the formation of an extra CNC–polymer network in addition to the CNC–CNC filler network present in the NR composite. The synergistic effect of the dual networks plays a key role in tuning the mechanical properties and water-responsive sensitivity for various potential biomedical applications. Our study further provides guidance to make use of renewable resources to produce high value added water-responsive nanocomposites.Keywords: cellulose nanocrystals (CNCs); dual network; epoxidized natural rubber (ENR); nanocomposites; water-responsive;
Co-reporter:Lei Wang, Yongxiang Shi, Sixian Chen, Wencai Wang, Ming Tian, Nanying Ning, Liqun Zhang
Chemical Engineering Journal 2017 Volume 314(Volume 314) pp:
Publication Date(Web):15 April 2017
DOI:10.1016/j.cej.2016.12.015
•Aramid fibers were modified by catechol/polyamine deposition and EGDE grafting.•The deposition process of catechol/polyamine was accelerated by UV irradiation.•The modified aramid fibers show an improved interfacial adhesion property with rubber matrix.A facile and efficient mussel-like inspired modification method was developed to improve the interfacial adhesion of aramid fibers/rubber composites. The surfaces of aramid fibers were pre-deposited by poly(catechol/polyamine) (PCPA) layer, which was formed via the oxidation polymerization of catechol/polyamine (CPA) under UV irradiation. Then, the PCPA-coated fibers were further grafted with ethylene glycol diglycidyl ether (EGDE) to introduce epoxy groups onto aramid fibers surface. The kinetics of catechol oxidation was investigated by UV–vis measurements, suggesting that UV irradiation accelerated the polymerization process of CPA. The effects of EGDE concentration and grafting time on the adhesion force between aramid fibers and rubber matrix were evaluated by pull-out test, and a maximum increase of 85.6% in adhesion force was achieved, even better than that by dopamine in our previous study (a 67.5% improvement). Compared with the method based on dopamine chemistry, this method has advantages of lower cost (less than 1% of the price of dopamine) and shorter reaction time (3 h less in pre-deposition time). This study provides a new efficient strategy for fibers surface functionalization, which has promising application in rubber industry.Download high-res image (72KB)Download full-size image
Co-reporter:Haibin Sun, Jing Hu, Xue Bai, Zhipeng Zheng, Zhanbin Feng, Nanying Ning, Liqun Zhang, Ming Tian
Polymer Testing 2017 Volume 64(Volume 64) pp:
Publication Date(Web):1 December 2017
DOI:10.1016/j.polymertesting.2017.10.012
•TPU/PLA composites with different phase morphology were prepared.•The toughness of PLA was significantly improved by controlling the morphology of TPU.•The toughening mechanism of TPU/PLA composites with different phase morphology of TPU was studied.•TPU/PLA composites exhibit significantly improved tensile toughness at low TPU content (20 wt%).•The toughening effect of TPU fibers or fiber network is much better than sea-island morphology at the same content.Oriented thermoplastic polyurethane (TPU) fiber and fiber network were first prepared by electrospinning. The as-prepared TPU fiber or fiber network was then pre-fixed in poly(lactic acid) (PLA)/TPU composite to improve the toughness of PLA. For comparison purpose, TPU/PLA composites with sea-island morphology were also prepared by traditional solution blending and mechanical blending. The results show that the toughness of PLA is greatly increased by the special pre-fixed oriented TPU fibers even at a low content, and the toughness is further increased by the TPU fiber network. Our results indicate for the first time that the toughening effect of special TPU fibers or fiber network is much better than that of traditional TPU with sea-island morphology. This study provides guidance to largely improve the toughness of PLA by designing the special phase morphology of TPU.
Co-reporter:Jing Bai, Qing He, Zixing Shi, Ming Tian, Hongjie Xu, Xiaodong Ma, Jie Yin
Polymer 2017 Volume 116(Volume 116) pp:
Publication Date(Web):5 May 2017
DOI:10.1016/j.polymer.2017.03.080
•C60 could be co-assembled into PB phase of the furan modified SBS via Diels-Alder (DA) reaction at the molecular level.•The morphology of SBS could be effectively tailored by addition of C60 and even small amount of C60 could lead to great change in the morphologies.•The hybrids based on SBS and C60 possessed the self-healing and remolding abilities via retro-Diels-Alder (rDA) reaction.In this article, C60 could be co-assembled into PB phase of the furan modified poly(styrene-b-butadiene-b-styrene) (SBS) via Diels-Alder (DA) reaction at the molecular level. The morphology of SBS could be effectively tailored by the incorporation of C60 and even small amount of C60 could lead to great change in the morphologies of SBS. Three types of morphologies of SBS could be observed as the content of C60 was increased from 0.1 to 2 wt%, which included honeycomb like, worm-like bi-continuous phase and their intermediate transition state. In the meantime, it was unexpectedly found that C60 could be used as effective crosslinking agents to build the network toward the furan modified SBS via DA reaction. Therefore, its solvent resistance, elastic resilience and tensile strength were greatly improved for the chemical crosslinking. Besides, due to the thermal reversible character for DA reaction, the hybrids based on SBS and C60 possessed the self-healing and remolding abilities via retro-Diels-Alder (rDA) reaction. All in all, C60 could provide the multiple functions toward the modification of SBS via DA reaction.Download high-res image (366KB)Download full-size image
Co-reporter:Shangqing Li, Yafei Lv, Jian Sheng, Hongchi Tian, Nanying Ning, Liqun Zhang, Hanguang Wu, Ming Tian
European Polymer Journal 2017 Volume 93(Volume 93) pp:
Publication Date(Web):1 August 2017
DOI:10.1016/j.eurpolymj.2017.06.019
•Mechanism on morphology development of POE/PP TPVs was deeply proposed.•POE/PP TPVs exhibits smaller rubber nanoparticles/agglomerates than EPDM/PP TPVs.•Higher degree of crosslinking accelerates the formation of rubber nanoparticles.•Higher shear rate and moderate crosslinking rate facilities the phase inversion.Polyolefin elastomer (POE)/polypropylene (PP) thermoplastic vulcanizates (TPVs) is considered to be a better alternative to commercial ethylene-propylene-diene monomer (EPDM)/PP TPVs owing to its better overall performance and low-cost. In this study, we deeply studied the morphology development of POE/PP blends during dynamic vulcanization (DV) and its influencing factors such as the degree of crosslinking, crosslinking rate and shear rate. The results show that POE/PP TPVs exhibits smaller rubber nanoparticles (RNPs) and their agglomerates than that of EPDM/PP TPVs because of the better compatibility between POE and PP. The morphology development during DV of POE/PP TPVs is dominated by the formation and agglomeration of POE RNPs caused by the combined effect of dynamical in-situ crosslinking and the shear-induced break-up of POE phase. Higher degree of crosslinking, higher shear rate and moderate crosslinking rate of POE phase facilitate the rapid formation of smaller RNPs and RNPs agglomerates, and accelerate the occurrence of faster phase inversion. This study provides guidance for the preparation of high performance POE/PP TPVs by controlling the microstructure.Higher degree of crosslinking, higher shear rate and moderate crosslinking rate of POE phase facilitate the rapid formation of smaller RNPs and RNPs agglomerates, and the occurrence of faster phase inversion.Download high-res image (110KB)Download full-size image
Co-reporter:Shuaichao Zhang, Yangcong Feng, Nanying Ning, Liqun Zhang, Ming Tian, Jianguo Mi
Computational Materials Science 2017 Volume 129(Volume 129) pp:
Publication Date(Web):1 March 2017
DOI:10.1016/j.commatsci.2016.12.010
In this article, the effects of nanorod–polymer interaction, aspect ratio of nanorods, block stiffness, and external tensile force on the microstructure and electrical properties of diblock copolymer nanocomposites have been investigated using molecular dynamics simulation. It is shown that, under suitable interactions of block-block and nanorod-block, a continuous localization of anisotropic nanorods in a continuous block with a slight uniaxial orientation can dramatically reduce the percolation threshold. Such effect is reinforced in the systems with high aspect ratio nanorods, but can be suppressed as block stiffness increases. Meanwhile, the external tensile strain breaks the continuity of the three-dimensional network but induces strong orientation along with the stretching direction, leading to a decrease of homogeneous probability and an increase of directional probability.Download high-res image (188KB)Download full-size image
Co-reporter:Nanying Ning;Xiangyan Li;Hongchi Tian;Yueqing Hua;Hongli Zuo;Pengjun Yao;Liqun Zhang;Youping Wu;Guo-Hua Hu
RSC Advances (2011-Present) 2017 vol. 7(Issue 9) pp:5451-5458
Publication Date(Web):2017/01/17
DOI:10.1039/C6RA24891H
This paper reports on the microstructure, morphological evolution and the properties of oil resistant nitrile butadiene rubber (NBR)/polypropylene (PP) thermoplastic vulcanizates (TPVs) prepared by dynamical vulcanization (DV). The as prepared NBR/PP TPVs exhibited good mechanical properties, good elasticity, easy processability and good oil resistance. Interestingly, the dispersed NBR microparticles in the NBR/PP TPVs were actually the agglomerates of secondary NBR microparticles with a diameter of about 1.7 μm and the phase inversion of the NBR/PP TPVs during DV was dominated by the formation and agglomeration of these secondary NBR microparticles. More interestingly, many PP domains were embedded in the dispersed crosslinked NBR phase, attributed to the chemical reaction between the compatibilizers amine-terminated butadiene-acrylonitrile copolymer (ATBN) and maleic anhydride grafted polypropylene (MP) and the voids among the spherical secondary NBR microparticles. As the DV proceeded, the size of the dispersed NBR agglomerates and the thickness of the PP ligaments in the NBR/PP TPVs decreased, leading to the increase in the density of the NBR agglomerates and the strengthening in the rubber network of the NBR/PP TPVs. As a result, the mechanical properties, the elasticity and the oil resistance of the NBR/PP TPVs were obviously improved as the DV proceeded.
Co-reporter:Yi Ye;Zhongjie Du;Liqun Zhang;Jianguo Mi
Physical Chemistry Chemical Physics 2017 vol. 19(Issue 1) pp:380-387
Publication Date(Web):2016/12/21
DOI:10.1039/C6CP07217H
We present a dynamic density functional approach to study polymer chain diffusion in a good solvent in the confinement of a nanopost array. Three key results emerge from our study. First, we show different scaling laws of the chains moving toward, close to, and around the posts. Second, in the flux process of polymer chains, the head, side, and middle segments display different scaling laws. As the chains come in contact with the posts, an enlarged motion discrepancy emerges between the head and middle segments perpendicular to the posts. For instance, the motion of head segments transforms from Zimm to reputation type, whereas the middle segments almost retain the Zimm motion. Third, as the spacing crack between two posts narrows down, a climbing effect along the posts can be clearly observed in the polymer motion.
Co-reporter:Yi Ye, Nanying Ning, Ming Tian, Liqun Zhang, and Jianguo Mi
Crystal Growth & Design 2017 Volume 17(Issue 1) pp:
Publication Date(Web):November 16, 2016
DOI:10.1021/acs.cgd.6b01289
We propose a dynamic density functional theory to describe the transition process from disordered liquid water to ordered ice crystal. With the special consideration of the enhanced and ordered hydrogen bonding in the crystal and the hydrodynamic interactions induced by the flow of water molecules, the theory is able to reproduce the process of nucleation and growth of ice crystal. Some theoretical predictions are in general agreement with the available computational and experimental data, indicating that the theory provides a reasonable description of the dynamic process of ice crystal growth.
Co-reporter:Haibin Sun, Chunyu Jiang, Nanying Ning, Liqun Zhang, Ming Tian and Shengli Yuan
Polymer Chemistry 2016 vol. 7(Issue 24) pp:4072-4080
Publication Date(Web):17 May 2016
DOI:10.1039/C6PY00581K
Herein, we report an approach to the preparation of a homogeneous styrene–butadiene–styrene triblock copolymer (SBS) dielectric elastomer (DE) with dramatically improved actuated strain by using a photochemical thiol–ene click reaction. The stock SBS was grafted with dipoles (ester groups) to increase the polarizability of SBS. The grafting degree of dipoles on SBS can be controlled by irradiation time to control its electromechanical properties. The grafting degree of modified SBS increases with the increase of irradiation time, and a maximum grafting degree of 81% can be achieved at a radiation time of 40 min. After modification, the phase mixing of PB and PS blocks occurs and the size of PS domains largely decreases, leading to the obvious decrease in the tensile strength and elastic modulus (Y). However, the modified SBS still shows good tensile strength (>3 MPa). More importantly, the dielectric constant (k) largely increases for the modified SBS. The simultaneous increase in k and decrease in Y result in a large increase in electromechanical sensitivity, and thus a large increase in maximum actuated strain and the actuated strain at low electric fields (e.g. 15 kV mm−1). In addition, the modified SBS shows consistently low dielectric loss. Our study provides a simple, effective and controllable chemical method to prepare a homogeneous DE with a high k, large actuated strain at a low electric field, good mechanical strength, easy processibility, and recyclability.
Co-reporter:Nanying Ning, Chunmeng Miao, Hua Zou, Qian Shao, Sishu Wang, Liqun Zhang, Ming Tian
Composites Science and Technology 2016 Volume 136() pp:46-52
Publication Date(Web):18 November 2016
DOI:10.1016/j.compscitech.2016.10.001
In this study, we introduced silver-coated glass particles (SG) into methyl vinyl silicone rubber (PMVS) matrix to prepare conductive elastomeric composites (CECs) with high electrical conductivity. The effect of the content of SG, the tensile strain and the stretch-recovery cycle times on the conductivity of CECs were studied. Interestingly, the conductivity of all the composites obviously increases with the increase in the applied tensile strain or the stretch-recovery cycle times to certain degree, different from that reported in many previous studies. The reason is that the dispersion of SG in PMVS matrix becomes more nonuniform with the increase in tensile strain, and the redistribution of SG in matrix results in the formation of much more new conductive network. On the other hand, the change in conductivity of the composites with the content of SG just exceeding the percolation threshold is much more significant than that with the content of SG far exceeding the percolation threshold. This is attributed to the more perfect conductive network in the composites with higher content of SG. The relationship between the conductivity and conductive filler network of SG/PMVS composites were clarified. This study provides guidance for the preparation and application of high performance CECs with excellent conductivity and stability of conductivity.
Co-reporter:Suting Liu, Haibin Sun, Nanying Ning, Liqun Zhang, Ming Tian, Wenjun Zhu, Tung W. Chan
Composites Science and Technology 2016 Volume 125() pp:30-37
Publication Date(Web):23 March 2016
DOI:10.1016/j.compscitech.2016.01.022
The liquid phase exfoliation (LPE) method, as a cheap, easily scalable, and eco-friendly method, was used to produce defect-free, unoxidized graphene. A surfactant-free technique was used to concentrate the graphene dispersion through stabilization by carbon nanotubes (CNTs) without functionalization. A special kind of aligned CNT bundles, which can be well dissociated into single CNTs in N-methyl-pyrrolidone by sonication, was used and fabricate Gr-CNT hybrid by π - π interaction. A redispersed stable Gr-CNT dispersion at a concentration of 2 mg mL−1 was used for preparing Gr-CNT/thermoplastic polyurethane (TPU) dielectric composite. The results show that the addition of 3.0 vol.% of hybrid improves the dielectric constant of the TPU greatly. As a result, a 10 times increase in electromechanical sensitivity (β) at 1000 Hz and 3.4 times increase in actuated strain at a low electric field (7.5 kV/mm) was achieved. The breakdown strengths of the Gr-CNT/TPU composites with 0.25 vol.% and 1.0 vol.% of hybrid are much higher than that of the pure TPU. As a result, the maximum actuated strain increases greatly from 4.8% for the pure TPU to 7% for the composite with 0.25 vol.% of the hybrid. Meanwhile, the energy density increases from 18 kJ/L for the pure TPU to 25 kJ/L and 48 kJ/L for the composites with 0.25 and 1.0 vol.% of hybrid, respectively.
Co-reporter:Hanguang Wu, Pengjun Yao, Nanying Ning, Liqun Zhang, Hongchi Tian, Youping Wu and Ming Tian
RSC Advances 2016 vol. 6(Issue 39) pp:32932-32939
Publication Date(Web):16 Mar 2016
DOI:10.1039/C6RA01463A
Thermoplastic vulcanizates (TPVs), as a special class of high-performance thermoplastic elastomers (TPEs), consist of a high content (60–80 wt%) of crosslinked rubber particles as the dispersed phase and a low content of a thermoplastic as the matrix. In this study, inspired by the special microstructure of TPVs, we prepared carbon nanotubes (CNTs)/TPV dielectric elastomer composites with a high dielectric constant (k) and low dielectric loss by constructing a dual network formed by rubber and CNTs. The rubber network was formed by a high content of agglomerates of rubber nanoparticles in the TPVs, which simultaneously promoted the formation of a CNTs network at a low content of CNTs in the matrix, to increase the value of k, and hindered the direct connection of CNTs with one another, to decrease the dielectric loss. As a result, the CNTs/TPV composites simultaneously possessed a high value of k and low dielectric loss. Moreover, the elasticity of the composites was improved by the CNTs because of the nanosprings of CNTs. This study provides a new simple and effective strategy for preparing a high-performance dielectric elastomer with a high value of k, low dielectric loss, good mechanical properties, high elasticity, high processability and easy recyclability.
Co-reporter:Pengjun Yao, Hanguang Wu, Nanying Ning, Liqun Zhang, Hongchi Tian, Youping Wu, Guohua Hu, Tung W. Chan and Ming Tian
RSC Advances 2016 vol. 6(Issue 14) pp:11151-11160
Publication Date(Web):15 Jan 2016
DOI:10.1039/C5RA26171F
We studied the microstructure, morphological evolution and the corresponding mechanism, and the properties of bromo-isobutylene-isoprene rubber (BIIR)/polypropylene (PP) thermoplastic vulcanizates (TPVs). Interestingly, a large number of single rubber nanoparticles were observed in the crosslinked BIIR/PP blends, ascribed to the improvement of compatibility between the BIIR and PP with increasing dynamic vulcanization (DV) time, as demonstrated by the increase in interfacial phase thickness and the decrease in the interfacial tension. Most of these single nanoparticles agglomerated as the DV proceeded, leading to the deterioration of the rubber network. Another interesting observation was that the size of rubber agglomerate decreased as the DV proceeded, leading to the strengthening of the rubber network. Importantly, the as-prepared BIIR/PP TPV exhibits good processability, high elasticity and good mechanical property. The relationship between the unique morphology and properties were studied. Our study provides guidance for the preparation of high-performance BIIR/PP TPV for its industrial applications such as medical bottle stoppers.
Co-reporter:Nanying Ning;Linjia Hu;Pengjun Yao;Hanguang Wu;Jibin Han;Liqun Zhang;Hongchi Tian
Journal of Applied Polymer Science 2016 Volume 133( Issue 8) pp:
Publication Date(Web):
DOI:10.1002/app.43043
ABSTRACT
In this study, polyamide-12 (PA12)/brominated isobutylene-isoprene (BIIR) TPVs with good mechanical properties and low gas permeability were prepared by dynamic vulcanization in a twin-screw extruder. The effects of three kinds of compatibilizers on the microstructure and properties of BIIR/PA12 TPV were studied. The compatibility between BIIR and PA12 was improved when maleated hydrocarbon polymeric compatibilizer is added. The reaction between maleic anhydride and amine in polyamide leads to the in situ formation of hydrocarbon polymer grafted polyamide which subsequently can be used to lower the interfacial tension between BIIR and polyamide. The compatibilizing effect of maleic anhydride modified polypropylene (PP-g-MAH) on BIIR/PA12 blends is the best among these compatibilizers because the surface energy of PP-g-MAH is very close to that of BIIR. The dispersed rubber phase of the blend compatibilized by PP-g-MAH shows the smallest size and more uniform size distribution, and the resulting TPVs show the best mechanical properties. The effects of fillers on the properties of BIIR/PA12 TPV were also investigated. The size of the BIIR phase increases with the increase in the content of CaCO3. The modulus and tensile strength of TPVs increased with the increase in the content of CaCO3 because of the reinforcing effect of CaCO3 on TPVs. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43043.
Co-reporter:Lei Wang, Yongxiang Shi, Rina Sa, Nanying Ning, Wencai WangMing Tian, Liqun Zhang
Industrial & Engineering Chemistry Research 2016 Volume 55(Issue 49) pp:
Publication Date(Web):November 16, 2016
DOI:10.1021/acs.iecr.6b03177
In this work, we develop a modified mussel-inspired method to enhance interfacial adhesion of aramid fiber to a rubber matrix. Through a simple dip-coating procedure, catechol and polyamine could initially codeposit as a poly(catechol-polyamine) (PCPA) coating on the surface of the aramid fiber. Then, the PCPA layer could be further grafted with silane coupling agent γ-(glycidyloxypropyltrimethoxysilane) (GPTMS). Results indicated that GPTMS was successfully grafted onto the aramid fiber surface via the bridging of the PCPA layer. The interfacial adhesion between the aramid fibers and the rubber matrix was improved compared to that achieved by polydopamine in our previous study. In addition, this method is more applicable to the rubber industry than polydopamine coating because of its cost-effectiveness and short reaction time.
Co-reporter:Hong Yao;Jia-li Niu;Jie Zhang;Nan-ying Ning
Chinese Journal of Polymer Science 2016 Volume 34( Issue 7) pp:820-829
Publication Date(Web):2016 July
DOI:10.1007/s10118-016-1794-4
The mechanical properties and phase morphologies of cis-1,4-butadiene rubber (BR) blended with polyethylene (PE) at different blend ratios were studied. The tensile test results show that the PE exhibits excellent reinforcing capabilities towards BR. Blending BR with PE results in a remarkable enhancement of tensile strength, modulus and the elongation at break simultaneously. An increment of tensile strength from 1.11 MPa to 16.26 MPa was achieved by incorporation of 40 wt% PE in the blends. The modulus and elongation at break of 40/60 PE/BR blends are also about 5 times higher than those of the pure BR treated under exactly the same conditions. The tear test indicates that the tear strength also increases with the increase of PE content. It reaches 58.38 MPa for the 40/60 PE/BR blend, which is approximately 10 times higher than that of the pure BR. Morphological study demonstrates that the PE forms elongated microdomains finely dispersed in the BR matrix when its content is over 30 wt%, which corresponds to the remarkably enhanced mechanical properties. According to the results, reinforcement mechanism of PE toward BR dependent on the microstructure has been discussed and two different mechanisms have been proposed.
Co-reporter:Ming Tian, Yang Yao, Suting Liu, Dan Yang, Liqun Zhang, Toshio Nishi and Nanying Ning
Journal of Materials Chemistry A 2015 vol. 3(Issue 4) pp:1483-1491
Publication Date(Web):17 Oct 2014
DOI:10.1039/C4TA04197F
We report the design and preparation of a separated-structured all-organic dielectric elastomer (DE) with large actuation strain under ultra-low voltage and high mechanical strength. Based on the protonic-conductivity mechanism of gelatin, a novel organic conductive filler with high dielectric constant and low elastic modulus was prepared by mixing gelatin and glycerol (GG). The separated structured DE was prepared by spraying a solution of GG into the multiple layers of thermoplastic polyurethane elastomer (TPU) nonwoven fabric by electrospinning, followed by hot pressing under vacuum. The densely packed TPU nonwoven fabric not only ensures the good mechanical strength of GG/TPU DE, but also separates GG filler and stops the formation of the GG continuous phase, preventing the formation of a conducting path under an exerted electric field. The novel GG filler considerably increases the dielectric constant and decreases the elastic modulus of the GG/TPU DE. As a result, the as-prepared DE exhibits good mechanical strength and 5.2% actuation strain at a very low electric field (0.5 kV mm−1). To the best of our knowledge, the required electric field for the same actuation strain is the lowest compared to other DE reported in the literature. Because all components in this composite are organic and biocompatible, this study offers a new method for preparing a DE with large actuation strain at low electric fields for its application in biological and medical fields, in which a low electric field is required.
Co-reporter:Nanying Ning, Qin Ma, Suting Liu, Ming Tian, Liqun Zhang, and Toshio Nishi
ACS Applied Materials & Interfaces 2015 Volume 7(Issue 20) pp:10755
Publication Date(Web):May 4, 2015
DOI:10.1021/acsami.5b00808
In this study, we obtained dielectric elastomer composites with controllable dielectric and actuated properties by using a biomimetic method. We used dopamine (DA) to simultaneously coat the graphene oxide (GO) and partially reduce GO by self-polymerization of DA on GO. The poly(dopamine) (PDA) coated GO (GO-PDA) was assembled around rubber latex particles by hydrogen bonding interaction between carboxyl groups of carboxylated nitrile rubber (XNBR) and imino groups or phenolic hydroxyl groups of GO-PDA during latex compounding, forming a segregated GO-PDA network at a low percolation threshold. The results showed that the introduction of PDA on GO prevented the restack of GO in the matrix. The dielectric and actuated properties of the composites depend on the thickness of PDA shell. The dielectric loss and the elastic modulus decrease, and the breakdown strength increases with increasing the thickness of PDA shell. The maximum actuated strain increases from 1.7% for GO/XNBR composite to 4.4% for GO-PDA/XNBR composites with the PDA thickness of about 5.4 nm. The actuated strain at a low electric field (2 kV/mm) obviously increases from 0.2% for pure XNBR to 2.3% for GO-PDA/XNBR composite with the PDA thickness of 1.1 nm, much higher than that of other DEs reported in previous studies. Thus, we successfully obtained dielectric composites with low dielectric loss and improved breakdown strength and actuated strain at a low electric field, facilitating the wide application of dielectric elastomers.Keywords: actuated strain; breakdown strength; dielectric properties; elastomer; poly(dopamine)-coated graphene oxide (GO-PDA);
Co-reporter:Hanguang Wu, Ming Tian, Liqun Zhang, Hongchi Tian, Youping Wu, Nanying Ning, and Tung W. Chan
ACS Sustainable Chemistry & Engineering 2015 Volume 3(Issue 1) pp:26
Publication Date(Web):November 19, 2014
DOI:10.1021/sc500391g
Thermoplastic vulcanizates (TPVs) have attracted considerable attention as typical “green” polymers in recent years and have been widely used in industry because they combine the excellent resilience of conventional elastomers and the easy recyclability of thermoplastics. With a new understanding of the formation and agglomeration of the rubber nanoparticles in ethylene propylene diene monomer/polypropylene (EPDM/PP) TPV, we revealed a new mechanism for the morphology evolution of TPV during dynamic vulcanization (DV). The phase inversion in TPV is dominated by the formation and agglomeration of the rubber nanoparticles rather than the elongation and breakup of the cross-linked rubber phase as previously reported. The size of the rubber agglomerates increases with increasing DV time and then remains constant after DV. In addition, we studied the relationship between the cross-linking of the rubber phase, formation and agglomeration of the rubber nanoparticles, and phase inversion and variation of the rubber network during DV. This study provides guidance to control the microstructure of TPV in preparation of high performance TPV products for automobile and electronic applications.Keywords: Atomic force microscopy (AFM); Dynamically vulcanized EPDM/PP blends; Mechanism; Morphology evolution; Phase inversion; Rubber network
Co-reporter:Nanying Ning, Lianjie Ji, Liqun Zhang, Jun Liu, Yonglai Lu, Shemao Wu, Hua Zou, Ming Tian, Tung W. Chan
Composites Science and Technology 2015 Volume 118() pp:78-84
Publication Date(Web):30 October 2015
DOI:10.1016/j.compscitech.2015.08.012
Previous studies using molecular simulation indicated that carbon nanotubes (CNTs) can act as nanosprings to adjust the viscoelasticity of elastomer composites. In this study, we prepared elastomer composites with both high elasticity and conductivity for the first time using carbon nanotubes array (CNTA) as nanosprings. A special CNTA bundle prepared by electrostatic self-assembly was directly blended with the polymethylvinylsiloxane (PMVS) matrix. The results indicated that these CNTAs were well dissociated into many single CNTs with almost no change in length in the PMVS matrix with low viscosity during mechanical shearing, and exhibited a nanospring effect. The CNTA composites exhibited not only higher conductivity and electromagnetic shielding effectiveness but also higher elasticity than the commonly used conductive carbon black composites at the same filler content. This study indicated that high performance conductive elastomer composites can be obtained by using special CNTAs as nanosprings.
Co-reporter:Rina Sa, Zhenhai Wei, Yan Yan, Lei Wang, Wencai Wang, Liqun Zhang, Nanying Ning, Ming Tian
Composites Science and Technology 2015 Volume 113() pp:54-62
Publication Date(Web):5 June 2015
DOI:10.1016/j.compscitech.2015.03.017
In this work, a combination of bio-inspired poly(dopamine) deposition and epoxy grafting was proposed, aiming at improving the surface activity and adhesion property of ultrahigh molecular weight polyethylene (UHMWPE) fibers. Inspired by adhesive proteins in mussels, dopamine self-polymerization was used to deposit a thin adherent poly(dopamine) (PDA) film onto the surface of UHMWPE fibers. Ethylene glycol diglycidyl ether (EGDE) was then grafted through the reactions with amide and imino groups of poly(dopamine) surface via a “two-step” or “one-step” method. The chemical structure and composition of fiber surface were characterized by XPS and ATR-IR. The surface hydrophilicity and wettability was determined by water contact angle (CA) measurement. SEM images revealed the morphology changes of the fibers. TGA and gravimetric method were applied for quantitative analysis of the surface treatment of each step. Epoxy value of modified fibers was evaluated by the titration method. The results confirmed that PDA was deposited and EGDE was successfully grafted onto the surface of fibers. The interfacial adhesion properties of UHMWPE fibers/rubber composites were investigated by single-fiber pull-out test, and 67.5% improvement was achieved. Resorcinol–formaldehyde–latex (RFL) dipping further enhanced the improvement to 365.4%. Catechol and epoxy grafted UHMWPE fabrics after dipping with RFL exhibited excellent adhesion properties with satisfying aging and fatigue resistance.
Co-reporter:Yang Yao, Nanying Ning, Liqun Zhang, Toshio Nishi and Ming Tian
RSC Advances 2015 vol. 5(Issue 30) pp:23719-23726
Publication Date(Web):24 Feb 2015
DOI:10.1039/C5RA00078E
Carbon nanospheres (CNS) were used as a new conductive filler to improve the electromechanical properties of a thermoplastic polyurethane (TPU) dielectric elastomer (DE). The results showed that CNS with many hydroxyl groups can form hydrogen bonds with TPU molecules, leading to a good dispersion of CNS in the TPU matrix and an improved tensile strength of CNS/TPU composites. More interestingly, CNS disrupted the crystallization of TPU, resulting in the decrease in elastic modulus and hysteresis loss of the composites. The dielectric constant at 1000 Hz increased from 7.1 for pure TPU to 137.3 for the composite with 5 wt% of CNS. The great increase in dielectric constant and the decrease in elastic modulus result in the largely improved actuation strain at low electric field of CNS/TPU composites. In addition, all the as-prepared CNS/TPU composites have a low dielectric loss (<1) at 1000 Hz. Our study provides a simple and effective way to obtain CNS/TPU DE with good mechanical strength and largely improved actuation performance at low electric field.
Co-reporter:Rina Sa, Yan Yan, Lei Wang, Yuan Li, Liqun Zhang, Nanying Ning, Wencai Wang and Ming Tian
RSC Advances 2015 vol. 5(Issue 114) pp:94351-94360
Publication Date(Web):27 Oct 2015
DOI:10.1039/C5RA19161K
In this research, ultraviolet (UV) irradiation induced graft polymerization of glycidyl methacrylate (GMA) was performed to modify the surface properties of poly-p-phenyleneterephthamide (PPTA) fibers. The improvement of adhesion with a rubber matrix was achieved due to the introduction of epoxy groups. The successful grafting of GMA on the PPTA fiber surface was ascertained by characterization using X-ray photoelectron spectroscopy (XPS), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), and scanning electron microscopy (SEM). The tensile properties of PPTA fibers after each stage of surface modification were determined by tensile testing of single-filaments. A single-fiber pull-out test was applied to evaluate the adhesion of PPTA fibers with the rubber matrix. The pull-out force of grafted PPTA fibers exceeded that of the pristine fibers by 53.7%. Resorcinol–formaldehyde–latex (RFL) dipping was applied to further improve the adhesion properties. As a result, the fibers with GMA grafting followed by RFL dipping exhibited a 80.8% improvement compared with the pristine fibers and achieved much higher adhesion strength with rubber matrix, compared to the PPTA fibers modified with conventional industrial method of isocyanate (NCO) and RFL two bath dipping.
Co-reporter:Zhaoyang Wei, Yaqi Hou, Nanying Ning, Liqun Zhang, Ming Tian, and Jianguo Mi
The Journal of Physical Chemistry B 2015 Volume 119(Issue 30) pp:9940-9948
Publication Date(Web):July 2, 2015
DOI:10.1021/acs.jpcb.5b01399
Silica nanoparticles dispersed in polystyrene, poly(methyl methacrylate), and poly(ethylene oxide) melts have been investigated using a density functional approach. The polymers are regarded as coarse-grained semiflexible chains, and the segment sizes are represented by their Kuhn lengths. The particle–particle and particle–polymer interactions are calculated with the Hamaker theory to reflect the relationship between particles and polymer melts. The effects of particle volume fraction and size on the particle dispersion have been quantitatively determined to evaluate their dispersion/aggregation behavior in these polymer melts. It is shown that theoretical predictions are generally in good agreement with the corresponding experimental results, providing the reasonable verification of particle dispersion/agglomeration and polymer depletion.
Co-reporter:Suting Liu, Ming Tian, Bingyue Yan, Yang Yao, Liqun Zhang, Toshio Nishi, Nanying Ning
Polymer 2015 Volume 56() pp:375-384
Publication Date(Web):15 January 2015
DOI:10.1016/j.polymer.2014.11.012
•We obtained a good dispersion and alignment of GONS in the TPU matrix.•We improved the dielectric constant by reducing GONS and disrupting hydrogen bonds.•We prepared dielectric elastomer with improved actuated strain at low voltage.Thermally reduced graphene oxide (TRG)/thermoplastic polyurethanes (TPU) dielectric elastomer with high dielectric constant (k), low dielectric loss and greatly improved actuated strain at low electric field was prepared by solution blending followed by in situ thermal reduction. The results showed that a good dispersion and alignment of TRG in the TPU matrix was obtained. The k at 103 Hz was sharply increased from 7 for pure TPU to 1875 for the composite with 2 vol. % of TRG because of the partial restoration of graphite structure and the great increase in dipole polarizability of TPU caused by the disruption of hydrogen bonds of TPU chains. The dielectric loss at 103 Hz of the composite with 2 vol. % of TRG remained low (0.43). Despite of the increase in elastic modulus with the increase in the content of TRG, the great increase in k lead to the great increase in electromechanical sensitivity (β). As a result, a 106 times increase in β at 103 Hz and 17 times increase in actuated strain at low electric field (250 V/mm) were achieved by adding 2.0 vol% of TRG. This study provides a simple and effective method for the improvement of actuated strain at low electric fields through partial reduction of graphene oxide and the disruption of hydrogen bonds in TPU, facilitating the applications of dielectric elastomers in the biological and medical fields, where a low electric field is required.
Co-reporter:Yi Ye
The Journal of Physical Chemistry C 2015 Volume 119(Issue 36) pp:20957-20966
Publication Date(Web):August 27, 2015
DOI:10.1021/acs.jpcc.5b05865
The wettability of rubbers with silica nanoparticle modification was investigated with theory and experiment. A simple coating technology was applied to generate the superhydrophobic styrene–butadiene rubber (SBR). Silica nanoparticles were covalently bonded with γ-methacryloxy propyl trimethoxysilane (γ-MPTMS), which was employed to improve coating durability through the thiol–ene click reaction with the SBR matrix. The contact angles of water droplets on the net and modified surfaces were then measured. The application of a three-dimensional density functional theory approach to predict the wetting contact angles showed that the chemical composition, chain conformation, and micro/nanostructure have different contributions to the hydrophobic behaviors. The theoretically predicted contact angles were partly validated by their experimental counterparts.
Co-reporter:Hongxia Li, Nanying Ning, Liqun Zhang, Yanxiang Wang, Wenli Liang, Ming Tian, Tung W. Chan
Polymer 2015 Volume 67() pp:1-11
Publication Date(Web):12 June 2015
DOI:10.1016/j.polymer.2015.04.027
•The effect of organophosphorus (OP) content on the flame retardancy and the flame retardancy mode of thermoplastic polyurethane (TPU) are reported.•The flame retardancy improved with increasing OP content. Potential reasons were discussed based on the morphology of the char layers resulting from the combustion of TPU blends.•The gas phase flame retardancy mode dominated in the composite with 20 wt% of OP by forming a loose, thin, and breakable porous char layer.•The condensed phase charring mode dominated for the composite with 40 wt% of OP by forming a continuous, thicker, and denser char layer during combustion, which acted as a more effective barrier to reduce heat feedback to the polymer surface.•This study indicated for the first time that the content of flame retardant plays an important role in the flame retardancy mode of OP for TPU.The effect of organophosphorus (OP) content on the flame retardancy and the flame retardancy mode of thermoplastic polyurethane (TPU) are reported. The limiting oxygen index (LOI) value for TPU increased from 23.1% to 24.6% and 33.5% by adding 20 wt% and 40 wt% of OP, respectively. UL-94 test showed V-2 rating for pure TPU, and V-1 rating and V-0 rating for the blends with 20 wt% and 40 wt% of OP, respectively. Potential reasons for the improved flame retardancy of TPU blends with increasing OP content were discussed based on the morphology of the char layers resulting from the combustion of TPU blends. The gas phase flame retardancy mode dominated in the composite with 20 wt% of OP by forming a loose, thin, and breakable porous char layer. The condensed phase charring mode dominated for the composite with 40 wt% of OP by forming a continuous, thicker, and denser char layer during combustion, which acted as a more effective barrier to reduce heat feedback to the polymer surface and thus resulted in the better flame retardancy. This study indicated for the first time that the content of flame retardant plays an important role in the flame retardancy mode of OP for TPU.
Co-reporter:Jing Bai, Zixing Shi, Jie Yin and Ming Tian
Polymer Chemistry 2014 vol. 5(Issue 23) pp:6761-6769
Publication Date(Web):26 Aug 2014
DOI:10.1039/C4PY00780H
We report an approach to the fabrication of nanostructured thermoplastic elastomeric composites based on poly(styrene-b-butadiene-b-styrene) (SBS) crosslinked by polyhedral oligomeric silsesquioxane (POSS). The crosslinking reaction took place between thiol functional groups from the POSS molecules and the double bonds within the soft block segment of SBS via UV-induced thiol–ene reaction. Unlike typical methods of constructing SBS composite systems, the triblock copolymer was directly used to produce SBS based composite materials with different loadings of POSS without any pre-chemical modification. In this system, the existence of covalent bonds between the inorganic nano-material (POSS) and the polymer matrix (SBS) promoted the compatibility of the composite material and POSS formed the cross-linking centers for the SBS. AFM measurements showed that good compatibility led the composite films to form well-ordered micro-phase separation at the nanoscale, and incorporation of POSS could effectively improve mechanical properties of SBS, including the storage modulus and strength without residual elongation in the cyclic tensile tests at very small loading.
Co-reporter:Yancong Feng, Nanying Ning, Qiangli Zhao, Jun Liu, Liqun Zhang, Ming Tian and Jianguo Mi
Soft Matter 2014 vol. 10(Issue 41) pp:8236-8244
Publication Date(Web):12 Aug 2014
DOI:10.1039/C4SM01119H
In this study, the effects of nanoparticle volume fraction, block stiffness, and diblock composition on the microstructure and electrical properties of composites are investigated using molecular dynamics simulation. It is shown that selective localization of conductive nanoparticles in a continuous block of diblock copolymer can dramatically reduce the percolation threshold. In the flexible–flexible copolymer systems with a relatively low particle loading, as the ratio of two blocks varies, one sees four kinds of phase structure: signal continuous, lamellar, co-continuous, and dispersed, corresponding to the order–disorder and continuity–dispersion transitions. In consideration of particle connectivity, the best electrical performance can be achieved with a special tri-continuous microstructure. While in the semi-flexible systems, the existence of rigid blocks can destroy the lamellar structure. If particles are located in the flexible block, a moderate stiffness of the rigid block can extensively enlarge the tri-continuous region, and high conductivity can be realized over a wide range of diblock compositions. If particles are located in the rigid block, however, high conductivity only emerges in a narrow composition range. In addition, the block should be prevented from becoming overstiff because this will cause direct particle aggregation.
Co-reporter:Hanguang Wu, Ming Tian, Liqun Zhang, Hongchi Tian, Youping Wu and Nanying Ning
Soft Matter 2014 vol. 10(Issue 11) pp:1816-1822
Publication Date(Web):08 Jan 2014
DOI:10.1039/C3SM52375F
The breakup of the rubber phase in an ethylene–propylene–diene monomer (EPDM)/polypropylene (PP) blend at the early stage of dynamic vulcanization is similar to that in an unvulcanized EPDM/PP blend because of the low crosslink density of the EPDM phase. In this work, the minimum size of the rubber phase in the unvulcanized EPDM/PP blend was first calculated by using the critical breakup law of viscoelastic droplets in a matrix. The calculated results showed that the minimum size of the rubber phase in the unvulcanized blend was in the nanometer scale (25–46 nm), not the micrometer scale as reported in many works. Meanwhile, the actual size of the rubber phase in the thermoplastic vulcanizate (TPV) at both the early stage and the final stage of dynamic vulcanization was observed by using peak force tapping atomic force microscopy (PF-AFM). The results indicated that the EPDM phase indeed broke up into nanoparticles at the early stage of dynamic vulcanization, in good agreement with the calculated results. More interestingly, we first revealed that the micrometer-sized rubber particles commonly observed in TPV were actually the agglomerates of rubber nanoparticles with diameters between 40 and 60 nm. The mechanism for the formation of rubber nanoparticles and their agglomerates during dynamic vulcanization was then discussed. Our work provides guidance to control the microstructure of the rubber phase in TPV to prepare high performance TPV products for a wide range of applications in the automobile and electronic industries.
Co-reporter:Nanying Ning, Suting Liu, Qian Shao, Shani Yan, Hua Zou, Liqun Zhang and Ming Tian
RSC Advances 2014 vol. 4(Issue 61) pp:32482-32489
Publication Date(Web):14 Jul 2014
DOI:10.1039/C4RA03786C
Nickel-coated graphite (NCG) with a layered structure and nickel-coated carbon fiber (NCF) with a fibrous structure were simultaneously introduced into a silicone matrix to prepare conductive elastomer composites (CECs) with high electrical conductivity and high conductivity stability. The effects of the volume fraction of fillers, the volume ratio of NCF/NCG, external strain and relaxation time on the conductivity and conductivity stability of the composites were studied. The results showed that the percolation threshold decreased with the increase in volume ratio of NCF/NCG. The conductivity and conductivity stability increased with the increase in the volume fraction of fillers, the volume ratio of NCF/NCG and the relaxation time, but decreased with the increase in external strain. The two dimensional morphology of the conductive filler network was characterized by using environmental scanning electron microscopy and the three dimensional network was characterized by using rubber processing analysis. The relationship between the conductive filler network and conductivity/conductivity stability is established for the first time to provide guidance for the preparation of high performance CECs.
Co-reporter:Nanying Ning, Xue Bai, Dan Yang, Liqun Zhang, Yonglai Lu, Toshio Nishi and Ming Tian
RSC Advances 2014 vol. 4(Issue 9) pp:4543-4551
Publication Date(Web):03 Dec 2013
DOI:10.1039/C3RA45769A
Aligned multi-walled carbon nanotubes (MWCNTs)/polyvinyl alcohol composite films were prepared by using an easy and controllable electrospinning-in situ film-forming (EF) technique. A high dielectric constant (k), a low dielectric loss, a consistently high breakdown strength, and a high energy density were obtained by using this technique. The dramatically improved dielectric properties are ascribed to the good dispersion and alignment of MWCNTs in the matrix, facilitating the formation of a large number of separated nano-capacitors (high k and low direct current (DC) conductance). For comparison purposes, the same composite films were prepared by solution casting (SC). At the same MWCNT content, the SC method yielded a higher k, but a significantly higher dielectric loss and much lower breakdown strength and energy density because of the random dispersion of MWCNTs in the matrix and the formation of a MWCNT network, which result in a large increase in DC conductance. The formation mechanism of the different microstructures and the relationships between the microstructures and dielectric properties are clarified. Our results indicate that high-performance MWCNTs/polymer dielectric composites can be obtained by controlling the microstructure of the composites by using the EF technique, which widens the applications of dielectric materials.
Co-reporter:Nanying Ning, Qin Ma, Yunqiang Zhang, Liqun Zhang, Hanguang Wu, Ming Tian
Polymer Degradation and Stability 2014 Volume 102() pp:1-8
Publication Date(Web):April 2014
DOI:10.1016/j.polymdegradstab.2014.01.037
In this work, zinc dimethacrylate (ZDMA) and 2-sulfur-benzimidazole (MB)/N-4(phenyl–phenyl)-maleimide (MC) were simultaneously used as synergistic antioxidants to improve the thermo-oxidative aging resistance of peroxide vulcanized ethylene-propylene-diene monomer (EPDM) for its application at high temperature. For comparison purpose, the control sample without antioxidants, the traditional antioxidant package, the combined antioxidant MB/MC, and pure ZDMA were also investigated. The results showed that the crosslinking density of EPDM was only slightly decreased before aging by using the combined antioxidant MB/MC/ZDMA, and the increase in crosslinking density was much less than other antioxidants at the same aging time, indicating the largely improved aging resistance of EPDM. As a result, the change in mechanical properties was the lowest for EPDM with the combined antioxidant MB/MC/ZDMA at high temperature. Meanwhile, the results from structure analysis showed that the degree of oxidation of EPDM was much lower than other systems after aging at 180 °C for 216 h by using the combined antioxidant MB/MC/ZDMA. In addition, the surfaces of EPDM samples with MB/MC/ZDMA as synergistic antioxidants or the combined antioxidant MB/MC were still smooth after aging at 180 °C for 216 h, whereas severe cracks occurred for other antioxidative systems. These results suggest the good thermo-oxidative aging resistance of the synergistic antioxidant MB/MC/ZDMA. Finally, the synergistic antioxidative mechanism of MB/MC/ZDMA was carefully discussed.
Co-reporter:Hongxia Li, Nanying Ning, Liqun Zhang, Yanxiang Wang, Wenli Liang, Ming Tian
Polymer Degradation and Stability 2014 Volume 105() pp:86-95
Publication Date(Web):July 2014
DOI:10.1016/j.polymdegradstab.2014.03.032
Co-reporter:Weidong Wu;Qi Chen;Yong Zhao;Xiaojing Ma;Hao Fong
Polymer Composites 2014 Volume 35( Issue 7) pp:1229-1237
Publication Date(Web):
DOI:10.1002/pc.22772
Three types of carbon nanoscale reinforcements (CNRs) including the shortened electrospun carbon nanofibers (ECNFs, with diameters and lengths of ∼200 nm and ∼15 µm, respectively), carbon nanofibers (CNFs), and graphite nanofibers (GNFs) were electrophoretically deposited on carbon fiber (CF) fabrics for the fabrication of hybrid multi-scale epoxy composites. The results indicated that the electrophoretic deposition (EPD) of CNRs onto CF fabrics led to substantial improvements on mechanical properties of hybrid multi-scale epoxy composites; in particular, the hybrid multi-scale epoxy composite containing surface-functionalized ECNFs (with amino groups) exhibited the highest mechanical properties. The study also indicated that some agglomerates of CNRs (particularly GNFs) could form during the EPD process, which would decrease mechanical properties of the resulting composites. Additionally, the reinforcement mechanisms were investigated, and the results suggested that continuous (or long) ECNFs would outperform short ECNFs on the reinforcement of resin-rich interlaminar regions in the composites. POLYM. COMPOS., 35:1229–1237, 2014. © 2013 Society of Plastics Engineers
Co-reporter:Pengjun Yao;Liqun Zhang;Hongchi Tian;Youping Wu;Nanying Ning
Journal of Applied Polymer Science 2014 Volume 131( Issue 18) pp:
Publication Date(Web):
DOI:10.1002/app.40765
ABSTRACT
Dynamic vulcanization to prepare blended thermoplastic vulcanizates (TPV) is a kind of complicated blending technology, where the breakup of the rubber phase happens accompanying with the crosslinking of rubber. In this study, we aim to investigate the effect of crosslinking on the breakup of chlorobutyl rubber (CIIR) phase in thermoplastic polyamide 12 (PA 12) matrix by purposely using pre-crosslinked CIIR with different crosslink degrees and plasticizer contents. Besides, the effect of blending conditions on the breakup of crosslinked CIIR phase was studied. The results show that a low crosslink degree, a high content of plasticizer, a low blending temperature and a morderate rotor speed of 70 rpm facilitate the breakup of pre-crosslinked CIIR in PA 12 matrix. This is ascribed to the decrease in the modulus of pre-crosslinked CIIR phase because of either a low crosslink degree or a high content of plasticizer, the increase in the molten viscosity of thermoplastic matrix because of a low blending temperature and a moderate rotor speed. It is indicated that the breakup of pre-crosslinked rubber is mainly dominated by the modulus of crosslinked rubber phase as well as the molten viscosity of thermoplastic matrix and shear stress. This study will provide guidance for the preparation of CIIR/PA TPV. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40765.
Co-reporter:Yancong Feng, Nanying Ning, Zhaoyang Wei, Liqun Zhang, Ming Tian, Hua Zou, Jianguo Mi
Polymer 2014 Volume 55(Issue 14) pp:3178-3185
Publication Date(Web):19 June 2014
DOI:10.1016/j.polymer.2014.05.012
We demonstrate that comprehensive electrical network and mechanical property of polymer nanocomposite (PNC) are coherently related to the specific dispersion of nanoparticles, which can be controlled by grafting like and unlike polymer chains. For PNC where the graft chain has the same chemistry as matrix, if the graft chains are relatively short, the grafted nanoparticle containing 0.4 chains in unit area can result in a loose and continuous percolating cluster, at which the optimized electrical and mechanical utilities can be achieved. At low grafting density (0.08 chains in unit area), the optimized characteristics can be fulfilled through extending the graft chain length to the ratio of 0.4 (graft chain length to matrix chain length). If the graft chain has different chemical structure, the optimum performance of PNC emerges at the low grafting density, where the matrix–graft interaction is 1.5 times the matrix–matrix interaction, and the ratio is 0.5.
Co-reporter:Xue Bai;Jing Zhang;Nanying Ning;Liqun Zhang;Toshio Nishi
Journal of Polymer Research 2014 Volume 21( Issue 5) pp:
Publication Date(Web):2014 May
DOI:10.1007/s10965-014-0436-1
In this work, an elastomeric Fe3O4 nano-particles (NPs)/polybutadiene rubber (BR) composite membrane was prepared by using the combined technique of electrospinning and in-situ crosslinking. The results showed that the saturation magnetization (Ms) and the coercive force (Hc) of the electrospun composite membrane with 5 wt.% Fe3O4 NPs was increased by 21 % and 69 %, respectively, comparing with the membrane prepared by solution casting. This was ascribed to the fine nano-dispersion of Fe3O4 NPs in BR matrix by using the electrospinning and in-situ crosslinking technique because the re-aggregation of Fe3O4 NPs was largely restrained by the fast evaporation of solvent, the confined space of nano/micro-sized fibers and the rapid crosslinking during electrospinning. Our work demonstrated that electrospinning and in-situ crosslinking is a simple and efficient method to improve the dispersion of nanoparticles in an elastomer matrix, and thus prepare high performance elastomeric nanocomposite.
Co-reporter:Jing Bai, Zixing Shi, Jie Yin, and Ming Tian
Macromolecules 2014 Volume 47(Issue 9) pp:2964-2973
Publication Date(Web):April 16, 2014
DOI:10.1021/ma5004024
Benzoxazine-functionalized poly(styrene-b-butadiene-b-styrene) (SBS) has been successfully synthesized via the thiol–ene click reaction. Unlike the typical method for fabrication of blends of SBS and thermosetting resins, the benzoxazine could be directly attached on to the chains of PB domains of this triblock copolymer without any prechemical modification for SBS via the incorporation of thiol functionalized benzoxazine (PTMP-BZ). AFM characterization shows that both thiol–ene and subsequent benzoxazine ring-opening reactions have a profound influence on the final morphologies of SBS, which undergoes great change from the cylinders for the pure SBS to different types of lamella structure for the SBS with different contents of the benzoxazines and the results obtained from AFM indicate that the interaction between PB and PS domains is strengthened after two reaction steps and this is responsible for the substantial improvement on the mechanical properties of material including tensile strength and storage modulus. In the meantime, the resilence of SBS is also improved significantly by the incorporation of benzoxazine and the modified SBS blends could recover its original shape without residual elongation after the tests of cyclic tensile stress–strain.
Co-reporter:Leilei Wang, Nanying Ning, Liqun Zhang, Yonglai Lu, Ming Tian, Tung Chan
Composites Part A: Applied Science and Manufacturing 2013 Volume 47() pp:135-142
Publication Date(Web):April 2013
DOI:10.1016/j.compositesa.2012.12.004
In this work, acrylonitrile–butadiene rubber/expanded graphite compounds with initial fine dispersion of nanosize graphite were prepared by latex compounding method, and then the dispersion evolution of the graphite during subsequent mixing and vulcanization was carefully investigated by using rubber process analysis, X-ray diffraction and transmission electron microscopy. The results showed that a significant filler network was already formed in the initial compounds because of the nanoscale dispersion and the high width/thickness ratio of graphite even at a content of less than 5 phr. During shearing, the graphite dispersion evolution is strongly related to the initial filler network. The filler network as well as the dispersion could also be obviously altered by changing the curing pressure and temperature during vulcanization, suggesting that the initial fine dispersion of graphite in the rubber/graphite nanocomposites could be maintained by reducing shear and by curing at a higher temperature and at a lower pressure.
Co-reporter:Hanguang Wu;Nanying Ning;Liqun Zhang;Hongchi Tian
Journal of Polymer Research 2013 Volume 20( Issue 10) pp:
Publication Date(Web):2013 October
DOI:10.1007/s10965-013-0266-6
Ethylene-Propylene-Diene Monomer/Polypropylene thermoplastic vulcanizates (EPDM/PP TPVs) have been widely used as a kind of typical “green” elastomer because of their excellent mechanical properties and recyclability. The industrial TPVs always contain various types of additives, which influence the viscosity ratio of EPDM and PP and the morphology of TPVs. This work studied the morphology evolution of EPDM/PP TPVs with various amounts of curing agents, fillers, and plasticizer during dynamic vulcanization in a twin-screw extruder, which provides much more complicated dynamic vulcanization process than haaker rheometer. The results show that the increased curing agents content leads to the faster morphology evolution of TPV because it enhances the cross-linking speed and the viscosity of EPDM. The increased fillers content leads to the later breakup of EPDM and the bigger size of the rubber aggregation because it enhanced the modulus of EPDM and weakens the interfacial interaction between EPDM and PP. In addition, the increase in the plasticizer content leads to the earlier breakup of EPDM and the larger size of the rubber phase in TPV. Our work firstly demonstrates the morphology evolution of industrial EPDM/PP TPV, and thus can provide a guidence for the industrial production of high-performance EPDM/PP TPVs.
Co-reporter:Haiyan Wu, Qinghua Hu, Liqun Zhang, Hao Fong, Ming Tian
Materials Letters 2012 Volume 84() pp:5-8
Publication Date(Web):1 October 2012
DOI:10.1016/j.matlet.2012.06.039
Herein we report an effective method for the preparation of composite nanofibers of polybutadiene rubber (BR) containing uniformly distributed Ag nanoparticles (Ag NPs). These nanofibers were morphologically stable and were made from electrospun core–sheath nanofibers with the sheath component being polyvinyl pyrrolidone (PVP) and the core component being BR, in situ synthesized Ag NPs, and a photo-curing agent of camphorquinone. The method included (1) co-axial electrospinning of core–sheath nanofibers, (2) in situ chemical crosslinking of BR in the core component of nanofibers, and (3) removal of the sheath component of PVP from nanofibers. The experimental observation indicated that, when the flow rate of inner spin dope was slower than that of the outer spin dope, the co-axial electrospinning process would be stable, the resulting nanofibers would not be curled; and there were few conglutination locations among the core–sheath nanofibers. Both electrospun core–sheath nanofibers and the resulting composite nanofibers possessed the cylindrical morphology with smooth surface. The study also revealed that the Ag in the composite nanofibers primarily existed in the elemental form.Highlights► Composite nanofibers of polybutadiene rubber (BR) and Ag nanoparticles (NPs) are made. ► The nanofibers are made via the technique of co-axial electrospinning. ► The BR/Ag NPs composite nanofibers possessed high morphological stability. ► An effective approach to avoid the conglutination of rubber nanofibers is reported.
Co-reporter:Yancong Feng, Hua Zou, Ming Tian, Liqun Zhang, and Jianguo Mi
The Journal of Physical Chemistry B 2012 Volume 116(Issue 43) pp:13081-13088
Publication Date(Web):October 11, 2012
DOI:10.1021/jp305815r
The dispersive and conductive properties of polymer nanocomposites are investigated simultaneously using the molecular dynamics simulation method. Four factors influencing the dispersion and conductivity are concerned, including polymer–nanoparticle interaction, nanoparticles with grafted chains, cross-linking of polymer chains, and blending of polymer. It is shown that the variation of the conductive probability is not linearly related to the corresponding dispersion for all the four concerned cases. As the interaction strength increases, the dispersion of the nanoparticles appears to first increase and then drop, while the conductive probability increases monotonously. Increase of the grafting density on nanoparticles can bring about the modification of the dispersion, whereas the variation of the conductive probability is M-type. The dispersion effect increases monotonously with the increasing cross-linking density, but the corresponding conductive probability appears to first increase and then drop. The dispersive effect of nanoparticles monotonously decreases as the ratio of added incompatible polymer increases; however, the corresponding conductive probability has the maximum value.
Co-reporter:Xiang Gao, Li-xin Mao, Ri-guang Jin, Li-qun Zhang and Ming Tian
Polymer Journal 2007 39(10) pp:1011-1017
Publication Date(Web):August 7, 2007
DOI:10.1295/polymj.PJ2006166
Polypropylene(PP)/ethylene-propylene-diene copolymer (EPDM)/fibrillar silicate attapulgite (AT) ternary blends were first prepared via the two-step melt blending process, by which the AT was blended with EPDM prior to compound with PP. Structure and mechanical properties of the blends were investigated. According to the analysis of TEM and DMA test, it was concluded that as for PP/EPDM/AT ternary blends, the typical “sea-island” morphology was observed, and the morphology of encapsulated structure like sandbag was formed in PP matrix besides neat EPDM dispersion domain, where EPDM encapsulated fibrillar silicate AT. The most-odds diameter (Dm), the number-average diameter (Dn) and the weight-average diameter (Dw) of dispersed particles decreased with increasing EPDM. PP/EPDM/AT ternary blends showed higher yield strength and dynamic modulus than the corresponding PP/EPDM binary systems due to the reinforcement of AT. PP/EPDM/AT ternary blend (100/20/5) possessed the balanced yield strength (21.9 MPa) and impact strength (47.7 kJ·m−2), relative to 23.0 MPa and 9.4 kJ·m−2 of PP. The micromechanical deformation process-mainly debonding of dispersed particles and shear yielding was mainly responsible for impact resistance of the ternary blends.
Co-reporter:Jinliang Qiao;Yuanwang Tang;Tie Li;Liqun Zhang;Yonglai Lu;Tie Li;Liqun Zhang;Yuanwang Tang;Yonglai Lu;Jinliang Qiao
Journal of Applied Polymer Science 2006 Volume 100(Issue 5) pp:3673-3679
Publication Date(Web):20 MAR 2006
DOI:10.1002/app.23202
A novel UFNBRP/EPDM blend was prepared by compounding ultra-fine full-vulcanized acrylonitrile butadiene rubber particles (UFNBRP) with ethylene–propylene–diene monomer (EPDM) matrix. The morphology, dynamic property, and curing property of the blend were discussed in detail. TEM and SEM observations showed that, no matter how high the blend ratio of UFNBRP to EPDM matrix was, UFNBRP particles always kept being in the dispersion phase because of its extremely high viscosity resulting from self-crosslinking, but were not dispersed as nanosize units, as expected. Dynamic properties, illustrated by DMTA, further demonstrated that two phases exhibited two separate glass transition temperatures, indicating distinct phase separation and weak phase interaction. Rubber processing analyzer results showed that inorganic filler as well as UFNBRP particles in EPDM matrix formed a network and blocked the flow properties of the compound. At the same time, the introduction of UFNBRP particles evidently affected the vulcanization of EPDM, when sulfur was used as a vulcanizing agent, and improved the mechanical properties of EPDM. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3673–3679, 2006
Co-reporter:Li-xin Mao;Xiang Gao;Ri-guang Jin;Li-qun Zhang
Macromolecular Materials and Engineering 2005 Volume 290(Issue 9) pp:899-905
Publication Date(Web):31 AUG 2005
DOI:10.1002/mame.200500004
Summary: Ternary nanocomposites based on polycarbonate (PC), poly(propylene) (PP), and attapulgite (AT) were prepared via the method of two-step melt blending, by which the AT was blended with PP prior to compound with PC. Structure and properties of the ternary PC/PP/AT nanocomposites were investigated. The degradation of PC triggered by AT during direct blending process can be inhibited effectively by using two-step melt blending. It was found that the morphology of encapsulation structure like sandbag was formed in PC matrix, where PP encapsulated AT fibrillar single crystals. DSC experiments showed that in PC/PP/AT ternary nanocomposites, AT had a strong heterophase nucleation effect on PP, resulting in the enhancement of crystallization degree and the crystallization temperature of PP. DMA and mechanical property results showed that the ternary nanocomposites exhibited good balanced toughness and stiffness.
Co-reporter:Zhaori Yu, Zixing Shi, Hongjie Xu, Xiaodong Ma, Ming Tian, Jie Yin
Carbon (April 2017) Volume 114() pp:
Publication Date(Web):April 2017
DOI:10.1016/j.carbon.2016.12.049
In this paper, we successfully prepared low-defect exfoliated graphene-based soft nacre-like composite film with superb elasticity and electrical conductivities, which is quite different from the conventional graphene oxide based film. Herein, we demonstrate a large-scale exfoliation process of graphite by incorporation of Myrtan Condensed Tannins (MCT), a natural polyphenol product extracted from bark of Arbutus. MCT could successfully produce large quantities of exfoliated graphene suspension (2.33 mg mL−1) with very few defects (ID/IG ∼ 0.27) in water, where more than 68% of these flakes are monolayer. Furthermore, via vacuum-assisted layer-by-layer self-assembled method, the soft and elastic exfoliated graphene-based nacre-like composite film was prepared using epoxy natural rubber (ENR) latex as crosslinking agent. Flexibility and stability of this graphene-based electrical conductive film are greatly enhanced at the same time. The composite films could be stretched by 20% of its initial length with 54 wt % of ENR in it and it could also be directly used as a conductive wire for an LED lamp with a conductivity of 157 S m−1. Most importantly, most of the raw materials used in this work are low cost natural products which is environmental-friendly and also suitable for production in large quantities.
Co-reporter:Nanying Ning, Shangqing Li, Haibin Sun, Yong Wang, Suting Liu, Yang Yao, Bingyue Yan, Liqun Zhang, Ming Tian
Composites Science and Technology (12 April 2017) Volume 142() pp:
Publication Date(Web):12 April 2017
DOI:10.1016/j.compscitech.2017.02.015
In this study, moderate content of polyethylene glycol (PEG) with ionic conductivity and low content of graphene oxide (GO) were simultaneously introduced into thermoplastic polyurethane (TPU) followed by in-situ chemical reduction of GO (rGO) to prepare TPU/PEG/rGO dielectric elastomer (DE) composites with largely improved electromechanical performance. The results showed that PEG remarkably disrupted the hydrogen bonds between TPU chains in TPU/PEG/rGO composites and formed new hydrogen bonds with TPU. In addition, PEG molecules can also form hydrogen bonds with rGO, leading to the coating of PEG on GO and thus the separation of rGO from TPU. Interestingly, PEG and rGO showed significant synergistic effect on the dielectric constant (ε′) of the composites, resulting in the large increase in ε′ at 103 Hz from 7 for pristine TPU to 71 for TPU/PEG/rGO composite. This was attributed to the increase in dipole polarizability of TPU chains caused by the disruption of hydrogen bonds and the increase in interfacial polarizability caused by the favorable electron transfer from partially reduced GO coated by PEG to TPU. The elastic modulus (Y) of the TPU/PEG/rGO composites largely decreased because of the plasticizing effect of PEG and the separation of GO from TPU. Owing to the simultaneous increase in ε′ and decrease in Y, the composite showed 49 times increase in electromechanical sensitivity (β) and 6.5 times increase in actuated strain at a certain electric field over that of pristine TPU.
Co-reporter:Yi Ye, Zhongjie Du, Ming Tian, Liqun Zhang and Jianguo Mi
Physical Chemistry Chemical Physics 2017 - vol. 19(Issue 1) pp:NaN387-387
Publication Date(Web):2016/11/16
DOI:10.1039/C6CP07217H
We present a dynamic density functional approach to study polymer chain diffusion in a good solvent in the confinement of a nanopost array. Three key results emerge from our study. First, we show different scaling laws of the chains moving toward, close to, and around the posts. Second, in the flux process of polymer chains, the head, side, and middle segments display different scaling laws. As the chains come in contact with the posts, an enlarged motion discrepancy emerges between the head and middle segments perpendicular to the posts. For instance, the motion of head segments transforms from Zimm to reputation type, whereas the middle segments almost retain the Zimm motion. Third, as the spacing crack between two posts narrows down, a climbing effect along the posts can be clearly observed in the polymer motion.
Co-reporter:Ming Tian, Yang Yao, Suting Liu, Dan Yang, Liqun Zhang, Toshio Nishi and Nanying Ning
Journal of Materials Chemistry A 2015 - vol. 3(Issue 4) pp:NaN1491-1491
Publication Date(Web):2014/10/17
DOI:10.1039/C4TA04197F
We report the design and preparation of a separated-structured all-organic dielectric elastomer (DE) with large actuation strain under ultra-low voltage and high mechanical strength. Based on the protonic-conductivity mechanism of gelatin, a novel organic conductive filler with high dielectric constant and low elastic modulus was prepared by mixing gelatin and glycerol (GG). The separated structured DE was prepared by spraying a solution of GG into the multiple layers of thermoplastic polyurethane elastomer (TPU) nonwoven fabric by electrospinning, followed by hot pressing under vacuum. The densely packed TPU nonwoven fabric not only ensures the good mechanical strength of GG/TPU DE, but also separates GG filler and stops the formation of the GG continuous phase, preventing the formation of a conducting path under an exerted electric field. The novel GG filler considerably increases the dielectric constant and decreases the elastic modulus of the GG/TPU DE. As a result, the as-prepared DE exhibits good mechanical strength and 5.2% actuation strain at a very low electric field (0.5 kV mm−1). To the best of our knowledge, the required electric field for the same actuation strain is the lowest compared to other DE reported in the literature. Because all components in this composite are organic and biocompatible, this study offers a new method for preparing a DE with large actuation strain at low electric fields for its application in biological and medical fields, in which a low electric field is required.
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