Co-reporter:Xingyi Huang
Advanced Materials 2015 Volume 27( Issue 3) pp:546-554
Publication Date(Web):
DOI:10.1002/adma.201401310
High-k polymer nanocomposites have considerable potential in energy storage and dielectric applications because of their ease of processing, flexibility, and low cost. Core–shell nanoarchitecture strategies are versatile and powerful tools for the design and synthesis of advanced high-k polymer nanocomposites. Recent and in-progress state-of-the-art advancements in the application of core–shell nanoarchitecture strategies to design and prepare high-k polymer nanocomposites are summarized. Special focus is directed to emphasizing their advantages over conventional melt-mixing and solution-mixing methods: first, homogeneous nanoparticle dispersion can be easily achieved even in highly loaded nanocomposites; second, the dielectric constant of the nanocomposites can be effectively enhanced and meanwhile the high breakdown strength can be well-preserved; third, for nanocomposites filled with electrically conductive nanoparticles, dielectric loss can be effectively surpressed, and meanwhile a high dielectric constant can be achieved. In addition, fundamental insights into the roles of the interfaces on the dielectric properties of the nanocomposites can be probed. The last part of the article is concluded with current problems and future perspectives of utilizing the core–shell nanoarchitecture strategies for the development of high-k polymer nanocomposites.
Co-reporter:Lijun Fang, Wei Wu, Xingyi Huang, Jinliang He, Pingkai Jiang
Composites Science and Technology 2015 Volume 107() pp:67-74
Publication Date(Web):11 February 2015
DOI:10.1016/j.compscitech.2014.12.009
Polymer composites with high thermal conductivity and high dielectric constant are highly desirable in electronic and electric industry, and particularly, for power apparatus at high voltages. In this work, a novel hydrangea-like ZnO superstructure was prepared by a template-free solvothermal method. Polyvinylidene fluoride (PVDF) composites filled with the ZnO superstructure were prepared via a solution mixing method. The microstructure, thermal conductivity, thermal stability and dielectric properties of the composites were investigated. It was found that the hydrangea-like ZnO shows marginal influence on microstructure of the PVDF matrix, but has significant enhancement effects on thermal conductivity, thermal stability and dielectric constant of the composites. Compared with the commercial ZnO nanoparticles, the hydrangea-like ZnO superstructures result in much higher enhancement of thermal conductivity and dielectric constant and slightly lower breakdown strength of the composites. This has been ascribed to the formation of percolation-like structure in the hydrangea-like ZnO composites.
Co-reporter:Jinhong Yu;Hailin Mo
Polymers for Advanced Technologies 2015 Volume 26( Issue 5) pp:514-520
Publication Date(Web):
DOI:10.1002/pat.3481
An efficient method was reported to fabricate boron nitride (BN) nanosheets using a sonication–centrifugation technique in DMF solvent. Then non-covalent functionalization and covalent functionalization of BN nanosheets were performed by octadecylamine (ODA) and hyperbranched aromatic polyamide (HBP), respectively. Then, three different types of epoxy composites were fabricated by incorporation of BN nanosheets, BN-ODA, and BN-HBP. Among all three epoxy composites, the thermal conductivity and dielectric strength of epoxy composites using BN-HBP nanosheets display the highest value, efficiently enhancing to 9.81 W/m K at 50 vol% and 34.8 kV/mm at 2.7 vol% (increase by 4057% and 9.4% compared with the neat epoxy), respectively. The significantly improved thermal conductivity and dielectric strength are attributed to the large surface area, which increases the contact area between nanosheets and nanosheets, as well as enhancement of the interfacial interaction between nanosheets and epoxy matrix. Copyright © 2015 John Wiley & Sons, Ltd.
Co-reporter:Ke Yang, Xingyi Huang, Lijun Fang, Jinliang He and Pingkai Jiang
Nanoscale 2014 vol. 6(Issue 24) pp:14740-14753
Publication Date(Web):03 Oct 2014
DOI:10.1039/C4NR03957B
Flexible nanodielectric materials with high dielectric constant and low dielectric loss have huge potential applications in the modern electronic and electric industry. Graphene sheets (GS) and reduced-graphene oxide (RGO) are promising fillers for preparing flexible polymer-based nanodielectric materials because of their unique two-dimensional structure and excellent electrical and mechanical properties. However, the easy aggregation of GS/RGO significantly limits the potential of graphene in enhancing the dielectric constant of polymer composites. In addition, the poor filler/matrix nanoscale interfacial adhesion also causes difficulties in suppressing the dielectric loss of the composites. In this work, using a facile and environmentally friendly approach, polydopamine coated RGO (PDA-RGO) and fluoro-polymer functionalized RGO (PF-PDA-RGO) were prepared. Compared with the RGO prepared by the conventional methods [i.e. hydrazine reduced-graphene oxide (H-RGO)] and PDA-RGO, the resulting PF-PDA-RGO nanosheets exhibit excellent dispersion in the ferroelectric polymer matrix [i.e. poly(vinylidene fluoride-co-hexafluoro propylene), P(VDF-HFP)] and strong interfacial adhesion with the matrix, leading to a low percolation threshold (fc = 1.06 vol%) and excellent flexibility for the corresponding nanocomposites. Among the three nanocomposites, the P(VDF-HFP)/PF-PDA-RGO nanocomposites exhibited the optimum performance (i.e. simultaneously having high dielectric constant and low dielectric loss). For instance, at 1000 Hz, the P(VDF-HFP) nanocomposite sample with 1.0 vol% PF-PDA-RGO has a dielectric constant of 107.9 and a dielectric loss of 0.070, showing good potential for dielectric applications. Our strategy provides a new pathway to prepare high performance flexible nanodielectric materials.
Co-reporter:Chao Wu, Lijun Fang, Xingyi Huang, and Pingkai Jiang
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 23) pp:21026
Publication Date(Web):November 7, 2014
DOI:10.1021/am505908d
Graphene foams have showed huge application potentials owing to their unique 3D structure and superior properties. Thus, it is highly desired to develop a simple and effective pathway to fabricate high performance graphene-based foams. Here, we present a polymer template-assisted assembly strategy for fabricating a novel class of graphene/AgNW hybrid foams. The hybrid foams show 3D ordered microstructures, high thermal stability, and excellent electrical and mechanical properties, and demonstrate huge application potential in the fields of flexible and stretchable conductors. Importantly, the polymer-template assisted assembly technique is simple, scalable, and low-cost, providing a new synthesis protocol for various multifunctional graphene hybrid foam-based composites.Keywords: assembly; flexible conductors; graphene; hybrid foams; silver nanowires
Co-reporter:Ke Yang, Xingyi Huang, Ming Zhu, Liyuan Xie, Toshikatsu Tanaka, and Pingkai Jiang
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 3) pp:1812
Publication Date(Web):January 7, 2014
DOI:10.1021/am4048267
Nanodielectric materials with high dielectric constant, low dielectric loss, and high energy storage capability are highly desirable in modern electric and electronics industries. It has been proved that the preparation of core–shell structured dielectric polymer nanocomposites via “grafting from” method is an effective approach to these materials. However, by using this approach, the deep understanding of the structure–dielectric property relationship of the core–shell structured nanodielectrics has been limited because of the lack of detailed information (e.g., molecular weight, grafting density) about the macromolecules grafted onto the nanoparticle surfaces. In this work, by the combination of reversible addition–fragmentation chain transfer (RAFT) polymerization and thiol–ene click reaction, two types of core–shell structured polymer@BaTiO3 (polymer@BT) nanocomposites with high dielectric constant and low dielectric loss were successfully prepared via a “grafting to” method. Compared with the “grafting from” method, this “grafting to” method has two merits: the molecular weight of the polymer chains in the shell layer can be easily controlled and the grafting density can be tailored by changing the molecular weight of the grafting polymer. Moreover, a clear insight into the relationship among the dielectric properties and energy storage capability of the core–shell structured polymer@BT nanocomposites, the molecular weight of the polymer chains, and the grafting density of the core–shell structured nanoparticles was achieved. The study provides new insights into the design and preparation of nanodielectric materials with desirable dielectric properties.Keywords: click reaction; core−shell structure; dielectric constant; dielectric loss; energy storage; nanocomposites; reversible addition−fragmentation chain transfer (RAFT) polymerization; thiol−ene;
Co-reporter:Lijun Fang, Chao Wu, Rong Qian, Liyuan Xie, Ke Yang and Pingkai Jiang
RSC Advances 2014 vol. 4(Issue 40) pp:21010-21017
Publication Date(Web):22 Apr 2014
DOI:10.1039/C4RA01194E
Polymer-based composites with high thermal conductivity and breakdown strength have become increasingly desirable in both the electronic and electric industries. Herein, we have designed a nano–micro structure of 2-D micro-scale hexagonal boron nitride (h-BN) and 0-D nano-scale α-alumina (α-Al2O3) hybrid fillers for epoxy composites with high thermal conductivity and breakdown strength. So as to improve interface interaction, both fillers are functionalized with hyperbranched aromatic polyamide (HBP). It is found that both structure design and surface modification play important roles. Surface modification can enhance many physical properties of composites, such as thermal conductivity, thermal stability and breakdown strength. Importantly, the nano–micro structure presents noticeable synergistic effects on both thermal conductivity and ac breakdown strength. The obtained composite with 26.5 vol% fillers presents a high thermal conductivity of 0.808 W m−1 K−1 (4.3 times that of epoxy). In addition, the breakdown strength of the composite at 4.4 vol% content is up to 40.55 kV mm−1, 21.5% higher than that of neat epoxy (33.38 kV mm−1).
Co-reporter:Chao Wu;Xingyi Huang;Xinfeng Wu;Rong Qian
Advanced Materials 2013 Volume 25( Issue 39) pp:5658-5662
Publication Date(Web):
DOI:10.1002/adma.201302406
Co-reporter:Chao Wu;Xingyi Huang;Genlin Wang;Libing Lv;Gan Chen;Guangyv Li
Advanced Functional Materials 2013 Volume 23( Issue 4) pp:506-513
Publication Date(Web):
DOI:10.1002/adfm.201201231
Abstract
Polymer-based materials with high electrical conductivity are of considerable interest because of their wide range of applications. The construction of a 3D, compactly interconnected graphene network can offer a huge increase in the electrical conductivity of polymer composites. However, it is still a great challenge to achieve desirable 3D architectures in the polymer matrix. Here, highly conductive polymer nanocomposites with 3D compactly interconnected graphene networks are obtained using a self-assembly process. Polystyrene (PS) and ethylene vinyl acetate (EVA) are used as polymer matrixes. The obtained PS composite film with 4.8 vol% graphene shows a high electrical conductivity of 1083.3 S/m, which is superior to that of the graphene composite prepared by a solvent mixing method. The electrical conductivity of the composites is closely related to the compact contact between graphene sheets in the 3D structures and the high reduction level of graphene sheets. The obtained EVA composite films with the 3D graphene structure not only show high electrical conductivity but also exhibit high flexibility. Importantly, the method to fabricate 3D graphene structures in polymer matrix is facile, green, low-cost, and scalable, providing a universal route for the rational design and engineering of highly conductive polymer composites.
Co-reporter:Ke Yang, Xingyi Huang, Yanhui Huang, Liyuan Xie, and Pingkai Jiang
Chemistry of Materials 2013 Volume 25(Issue 11) pp:2327
Publication Date(Web):May 16, 2013
DOI:10.1021/cm4010486
Polymer nanocomposites with high energy density and low dielectric loss are highly desirable in electronic and electric industry. Achieving the ability to tailor the interface between polymer and nanoparticle is the key issue to realize desirable dielectric properties and high energy density in the nanocomposites. However, the understanding of the role of interface on the dielectric properties and energy density of polymer nanocomposites is still very poor. In this work, we report a novel strategy to improve the interface between the high dielectric constant nanoparticles (i.e., BaTiO3) and ferroelectric polymer [i.e., poly(vinylidene fluoride-co-hexafluoro propylene)]. Core–shell structured BaTiO3 nanoparticles either with different shell thickness or with different molecular structure of the shell were prepared by grafting two types of fluoroalkyl acrylate monomers via surface-initiated reversible addition–fragmentation chain transfer (RAFT) polymerization. The dielectric properties and energy storage capability of the corresponding nanocomposites were investigated by broadband dielectric spectroscopy and electric displacement-electric field loop measurement, respectively. The results show that high energy density and low dielectric loss are successfully realized in the nanocomposites. Moreover, the energy storage densities of the P(VDF-HFP)-based nanocomposites could be tailored by adjusting the structure and thickness of the fluoro-polymer shell. The approach described is applicable to a wide range of nanoparticles and polymer matrix, thereby providing a new route for preparing polymer-based nanocomposites used in electronic and electric industry.Keywords: dielectric loss; energy density; interface; polymer nanocomposites; RAFT polymerization;
Co-reporter:Chao Wu, Xingyi Huang, Xinfeng Wu, Liyuan Xie, Ke Yang and Pingkai Jiang
Nanoscale 2013 vol. 5(Issue 9) pp:3847-3855
Publication Date(Web):25 Mar 2013
DOI:10.1039/C3NR00625E
Polymer-based materials with a high dielectric constant show great potential for energy storage applications. Since the intrinsic dielectric constant of most polymers is very low, the integration of carbon nanotubes (CNTs) into the polymers provides an attractive and promising way to reach a high dielectric constant owing to their outstanding intrinsic physical performances. However, these CNT-based composites usually suffer from high dielectric loss, low breakdown strength and the difficulty to tailor the dielectric constant. Herein, we have designed and fabricated a new class of candidates composed of graphene oxide-encapsulated carbon nanotube (GO-e-CNT) hybrids. The obtained GO-e-CNT–polymer composites not only exhibit a high dielectric constant and low dielectric loss, but also have a highly enhanced breakdown strength and maximum energy storage density. Moreover, the dielectric constant of the composites can be tuned easily by tailoring the loading of GO-e-CNTs. It is believed that the GO shells around CNTs play an important role in realizing the high dielectric performances of the composites. GO shells can not only effectively improve the dispersion of CNTs, but also act as insulation barriers for suppressing leakage current and increasing breakdown strength. Our strategy provides a new pathway to achieve CNT-based polymer composites with high dielectric performances for energy storage applications.
Co-reporter:Liyuan Xie, Xingyi Huang, Yanhui Huang, Ke Yang, and Pingkai Jiang
ACS Applied Materials & Interfaces 2013 Volume 5(Issue 5) pp:1747
Publication Date(Web):February 4, 2013
DOI:10.1021/am302959n
Polymer nanocomposites with the dielectric constant comparable to that of percolative composites are successfully prepared by using core–shell structured hyperbranched aromatic polyamide grafted barium titanate (BT-HBP) hybrid nanofiller. Poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) (PVDF-TrFE-CFE) was used as the polymer matrix because of its high intrinsic dielectric constant and easy processability. The BT-HBP hybrid nanofiller were prepared by a solution polymerization of diaminobenzoic acid on the surface of amino-funcationalized BT nanoparticles. Nuclear magnetic resonance (1H NMR) and transmission electron microscopy (TEM) were used to verify the chemical structure of the hyperbranched aromatic polyamide and core-shell structure of the hybrid filler, respectively. It was found that the nanocomposite with 40 vol % BaTiO3–HBP had a dielectric constant of 1485.5 at 1000 Hz, whereas the corresponding nanocomposite sample with untreated BaTiO3 only showed a dielectric constant of 206.3. Compared with classic percolative composites, the advantage of the PVDF-TrFE-CFE/BaTiO3–HBP nanocomposites is that the composites show high enough breakdown strength and high dielectric constant simultaneously. An enhanced interfacial polarization mechanism between the BT-HBP and the polymer matrix was suggested for understanding the observed unusually high dielectric constant.Keywords: barium titanate nanoparticles; core−shell structure; high dielectric constant; interfacial polarization; poly (vinylidene fluoride-trifluoroethylene-chlorofluoroethylene);
Co-reporter:Rong Qian, Jinhong Yu, Chao Wu, Xing Zhai and Pingkai Jiang
RSC Advances 2013 vol. 3(Issue 38) pp:17373-17379
Publication Date(Web):23 Jul 2013
DOI:10.1039/C3RA42104J
Graphene has attracted considerable attention as a promising candidate to improve the thermal conductivity of polymers owing to its extremely high intrinsic thermal conductivity (∼5300 W m−1 K). However, graphene-based composites show a high electrical conductivity even with a low loading of fillers, which greatly limits their applications in electronic devices. Herein, we present a new class of fillers of alumina-coated graphene sheet (GS@Al2O3) hybrid fillers via an electrostatic self-assembly route. This unique structural design combines the advantages of both the GS and Al2O3, resulting in PVDF/GS@Al2O3 composites that show not only high thermal conductivity, but also retain high electrical insulation. For instance, the thermal conductivity of PVDF composites with 40 wt% GS@Al2O3 is up to 0.586 W m−1 K and the volume resistivity is above 4 × 1014 Ω cm. Moreover, this self-assembly route is a simple and scalable strategy for fabricating high performance thermally conductive materials.
Co-reporter:J. Jiang;Y. Zhang;Y. Zheng;P. Jiang
Chemical Engineering & Technology 2013 Volume 36( Issue 8) pp:1371-1377
Publication Date(Web):
DOI:10.1002/ceat.201300106
Abstract
Solid catalysts, Li-Al layered double hydroxides (Li-Al LDHs), were prepared to catalyze the transesterification of soybean oil (SBO) with ethylene glycol. To improve catalytic activity, the Li-Al LDHs were modified by calcination and further modification after calcination with a silane coupling agent containing amine groups. Calcination caused the change of the catalysts' structure from a double-layer structure to porous particle and the specific surface area highly increased. After modification with a silane coupling agent, the average pore diameter increased. The two methods had a similar effect on catalytic activity improvement. However, modifying with a coupling agent can sharply decrease the catalysts' regeneration temperature. Furthermore, catalyst recycling and regeneration, along with the effects of temperature, time, agitation, and ratio between SBO and ethylene glycol on transesterification were studied.
Co-reporter:Rong Qian;Jinhong Yu;Liyuan Xie;Yanan Li
Polymers for Advanced Technologies 2013 Volume 24( Issue 3) pp:348-356
Publication Date(Web):
DOI:10.1002/pat.3090
Aluminum nitride (AlN) nanoparticles were firstly treated with a silane coupling agent, γ-aminopropyl-triethoxysilane (γ-APS), to introduce amine groups (AlN-APS), then grafting of the hyperbranched aromatic polyamide started from the modified surface (AlN-HBP). The surface modified AlN nanoparticles were characterized by Fourier transform infrared, nuclear magnetic resonance, and thermogravimetric analyzer. Then the nanoparticles with these three different interface structures were selected as reinforcing fillers for epoxy composites. The study reports the influence of interfacial structure of nanoparticles on the morphology and thermal properties of epoxy composites. It was found that the AlN-HBP nanoparticles result in a strong interface and thus the incorporation of the AlN-HBP nanoparticles not only improved the dispersion of the nanoparticles in the epoxy matrix but also enhanced the thermal conductivity, thermal stability, glass transition temperatures, and dynamical thermomechanical properties. Copyright © 2013 John Wiley & Sons, Ltd.
Co-reporter:Xinfeng Wu, Jianqiang Zhang, Chao Wu, Genlin Wang, Pingkai Jiang
Wear 2013 Volume 297(1–2) pp:742-751
Publication Date(Web):15 January 2013
DOI:10.1016/j.wear.2012.10.017
Trimethylolpropane trimethacrylate (TMPTMA) and tripropylene glycol diacrylate (TPGDA) used as crosslinking agents were blended with ultra-high molecular weight polyethylene (UHMWPE or UPE) in alcohol, respectively. Then UPE plates were made by compression molding and electron beam (EB) irradiation crosslinking methods. FTIR, Soxhlet extractor, DSC, Wear tester and SEM were used for the characterization of all specimens. FTIR analyses show that trans-vinylene (965 cm−1) absorption increases in all specimens and the >C=C< stretching absorption decreases after irradiation. Soxhlet experiments reveal that gel fraction increases with the increasing dose. DSC results indicate that Xc of all the irradiated UPEs are higher than that of unirradiated UPEs because of the free radical and small molecular which can promote the crystallization. Wear rate of 100 kGy 1%TMPTMA/UPE and 1%TPGDA/UPE are 1.89×10−7 mm3/(N m) and 4.28×10−7 mm3/(N m), about 44.2% and 100% of that of 100 kGy UPE, respectively, illustrating that TMPTMA is beneficial to reduce the wear rate of UPE and TPGDA almost has no effect to reduce the wear rate of UPE before 100 kGy. SEMs of irradiated specimens are more smooth than that of unirradiated specimens. These can give some advice to improve tribological properties of UPE used in the friction field.Highlights► TMPTMA and TPGDA were blended with UPE in alcohol, respectively. ► Then UPE plates were made by compression molding and EB irradiation crosslinking methods. ► TMPTMA and TPGDA were used to increase the crosslinking density of UPE. ► Wear rate of 100 kGy 1%TMPTMA/UPE is 44.2% of that of 100 kGy UPE.
Co-reporter:Liyuan Xie, Xingyi Huang, Yanhui Huang, Ke Yang, and Pingkai Jiang
The Journal of Physical Chemistry C 2013 Volume 117(Issue 44) pp:22525-22537
Publication Date(Web):October 4, 2013
DOI:10.1021/jp407340n
Polymer nanocomposites with high dielectric constant have extensive applications in the electronic and electrical industry because of ease of processing and low cost. Blending and in situ polymerization are two conventional methods for the preparation of polymer nanocomposites. However, the resulting nanocomposites, particularly highly filled nanocomposites, generally have some disadvantages such as high dielectric loss and low dielectric constant and thus show low energy density and low energy efficiency. Here we developed a core@double-shell strategy to prepare barium titanate (BT)-based high performance polymer nanocomposites, in which the first shell is hyperbranched aromatic polyamide (HBP) and the second shell is poly(methyl methacrylate) (PMMA). This method utilized the advantages of both polymer shells, resulting in superior dielectric property which cannot be achieved in nanocomposites prepared by the conventional blending methods. It is found that, compared with the conventional solution blended BT/PMMA nanocomposites, the core@double-shell structured BT@HBP@PMMA nanocomposites had higher dielectric constant and lower dielectric loss. The energy densities of BT@HBP@PMMA nanocomposites were higher than that of BT/PMMA nanocomposites accordingly. The dielectric response of the nanocomposites was analyzed, and the mechanisms resulting in the higher dielectric constant and lower dielectric loss in BT@HBP@PMMA nanocomposites were proposed. This study suggests that the core@double-shell strategy shows strong potential for preparing polymer nanocomposites with desirable dielectric properties.
Co-reporter:Chao Wu, Xingyi Huang, Genlin Wang, Xinfeng Wu, Ke Yang, Shengtao Li and Pingkai Jiang
Journal of Materials Chemistry A 2012 vol. 22(Issue 14) pp:7010-7019
Publication Date(Web):02 Mar 2012
DOI:10.1039/C2JM16901K
The incorporation of graphene sheets (GSs) into polymer matrices affords engineers an opportunity to synthesize polymer composites with excellent physical performances. However, the development of high performance GS-based composites is difficult because of the easy aggregation of GSs in a polymer matrix as well as the weak interfacial adhesion between GSs and the host polymer. Herein, we present a simple and effective route to hyperbranched aromatic polyamide functionalized graphene sheets (GS–HBA). The resulting GS-HBA exhibits uniform dispersion in a thermoplastic polyurethane (TPU) matrix and strong adhesion with the matrix by hydrogen-bond coupling, which improve the load transfer efficiency from the matrix to the GSs. Thus, the GS–HBA–TPU composites possess excellent mechanical performance and high dielectric performance. It has been demonstrated that the GS–HBA composite has higher modulus, higher tensile strength and higher yield strength, and remains at nearly the same strain at break when compared with the composites with graphene oxide, ethylene diamine-modified graphene, and hydrazine reduced graphene. In addition, the hyperbranched polymer chains allow construction of a large number of microcapacitors and suppress the leakage current by isolating the GSs in a TPU matrix, resulting in a higher permittivity and lower loss tangent for the GS–HBA composite in comparison with ethylene diamine-modified graphene, or hydrazine reduced-graphene composites.
Co-reporter:Mi Li, Xingyi Huang, Chao Wu, Haiping Xu, Pingkai Jiang and Toshikatsu Tanaka
Journal of Materials Chemistry A 2012 vol. 22(Issue 44) pp:23477-23484
Publication Date(Web):08 Oct 2012
DOI:10.1039/C2JM34683D
Novel polyaniline decorated reduced graphene oxide (rPANI@rGO) two-dimensional (2D) hybrids sheets were successfully prepared by in situ polymerization of aniline on graphene oxide (GO) sheets and successive reduction by hydrazine. PANI is heavily reduced, thus it is electrically insulating. The hybrid sheets were used as a novel filler for high performance poly(methyl methacrylate) (PMMA) nanocomposites. Our results show that, when compared with the PMMA/rGO composites, the PMMA/rPANI@rGO nanocomposites not only show a high dielectric constant but also have low dielectric loss. For example, at 1000 Hz, a dielectric constant of 40 and a dielectric loss of 0.12 were observed in the PMMA/rPANI@rGO nanocomposite with rGO/PMMA volume ratio of 6%, whereas the dielectric constant and dielectric loss of PMMA/rGO composite with rGO/PMMA volume ratio of 6% are about 20 and 1250, respectively. More importantly, the dielectric properties of PMMA/rPANI@rGO nanocomposites can be tuned by controlling the addition of the hybrid sheets. The improved dielectric properties in PMMA/rPANI@rGO nanocomposites should originate from the isolation effect of rPANI on the rGO in PMMA matrix, which not only improves the dispersion of rGO but also hinders the direct electrical contact between rGO. This research sets up a novel route to polymer composites with high dielectric constants and low dielectric loss, and also expands the application space of graphene-based fillers.
Co-reporter:Ke Yang;Xingyi Huang;Liyuan Xie;Chao Wu;Toshikatsu Tanaka
Macromolecular Rapid Communications 2012 Volume 33( Issue 22) pp:1921-1926
Publication Date(Web):
DOI:10.1002/marc.201200361
Abstract
A novel route to prepare core–shell structured nanocomposites with excellent dielectric performance is reported. This approach involves the grafting of polystyrene (PS) from the surface of BaTiO3 by an in situ RAFT polymerization. The core–shell structured PS/BaTiO3 nanocomposites not only show significantly increased dielectric constant and very low dielectric loss, but also have a weak frequency dependence of dielectric properties over a wide range of frequencies. In addition, the dielectric constant of the nanocomposites can also be easily tuned by varying the thickness of the PS shell. Our method is very promising for preparing high-performance nanocomposites used in energy-storage devices.
Co-reporter:Junqing Jiang, Yanwu Zhang, Liwei Yan, Pingkai Jiang
Applied Surface Science 2012 Volume 258(Issue 17) pp:6637-6642
Publication Date(Web):15 June 2012
DOI:10.1016/j.apsusc.2012.03.095
Abstract
{PO4[W(O)(O2)2]4}3− was supported onto modified halloysite nanotubes (HNTs) to prepare heterogeneous catalysts and these catalysts were applied in epoxidation of soybean oil. To enhance the cohesive force between {PO4[W(O)(O2)2]4}3− and HNTs, quaternary amino groups were anchored onto HNTs through silylation of N-(2-aminoethyl)-3-aminopropyl trimethoxysilane and alkylation of amino groups. Further {PO4[W(O)(O2)2]4}3− was supported onto HNTs by ion exchange. The heterogeneous catalysts were characterized by FTIR, TGA, XRF and TEM–EDS. Then the catalytic behaviour to epoxidation of soybean oil was studied in detail. The results show that the introduction of phase transfer agent during preparation of the catalysts is very effective to improve catalytic activity and mechanical agitation combining with ultrasonic agitation is the best agitation way. The catalytic reactivity increased as reaction time increased. Moreover, the catalysts can be easily recovered from the reaction system by centrifugation as deposit and recycled three times without obviously decreasing the catalytic activity. Through re-exchange of {PO4[W(O)(O2)2]4}3−, the heterogeneous catalyst can be regenerated without catalytic activity loss.
Co-reporter:Zongliu Tang, Yanan Li, Yong Jian Zhang, Pingkai Jiang
Polymer Degradation and Stability 2012 Volume 97(Issue 4) pp:638-644
Publication Date(Web):April 2012
DOI:10.1016/j.polymdegradstab.2012.01.002
Co-reporter:Xinfeng Wu, Lichun Wang, Chao Wu, Jinhong Yu, Liyuan Xie, Genlin Wang, Pingkai Jiang
Polymer Degradation and Stability 2012 Volume 97(Issue 1) pp:54-63
Publication Date(Web):January 2012
DOI:10.1016/j.polymdegradstab.2011.10.011
Graphite (expanded graphite(EG), natural graphite (NG) and graphite oxide (GO)) flame retardant poly(ethylene-co-vinyl acetate) copolymer (EVA) composites (EVA/EG, EVA/NG and EVA/GO) have been prepared by melt compounding. The flammability, the combustion process, the quantity of the residual char, the morphology of the residual chars and the thermal stability of the chars were investigated by cone calorimeter, SEM and TGA. The results indicate that heat release rate (HRR), total heat released (THR) and total smoke release (TSR) of EVA/EG (EG 30 phr) composite decrease to about 21%, 42% and 28% of that of pure EVA, respectively. The orders of the three kinds of graphite on the reduction effect of THR and TSR are EG > NG > GO. The higher the quantity, the higher is the thermal stability of the char residue and the more compact and porous char structure may be the main reasons for the phenomenon above. It has been found that the flame retardance of EVA vulcanisates is improved and the fire jeopardizing is dramatically reduced due to the addition of the graphite, especially for EG, which can give some advice to design formulations for practical applications as the jackets of cables.
Co-reporter:Jingkuan Duan;Jun Zhang
Journal of Applied Polymer Science 2012 Volume 125( Issue 2) pp:902-914
Publication Date(Web):
DOI:10.1002/app.33368
Abstract
In this article, the influences of the external electric field exerted to the curing epoxy and epoxy/acrylate systems on their cured microstructures and macroscopic performances were investigated by means of morphological investigation and some characteristic analyses. Epoxy and epoxy/acrylate (an interpenetrating polymer network) systems were subjected to the action of the alternating electric field during the curing process. The changes in the nanolamellae microstructure in the cured epoxy and the nanoellipsoid microstructure in the cured epoxy/acrylate systems resulting from the electric field treatment were observed using atomic force microscopy. Dynamic mechanical analysis showed that the external electric field treatment made the low and high relaxation peaks shift to the lower and higher temperatures, respectively. Thermogravimetric analysis implied that the curing reactions of the epoxy systems with the aid of the external electric field resulted in some negative influences on their thermal stability. The dielectric measurements demonstrated that the electrical properties of the epoxy system for vacuum pressure impregnation insulation of the high-voltage electric machines could be much improved with the aid of the external electric field. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Co-reporter:Xingyi Huang, Chunyi Zhi, and Pingkai Jiang
The Journal of Physical Chemistry C 2012 Volume 116(Issue 44) pp:23812-23820
Publication Date(Web):October 22, 2012
DOI:10.1021/jp308556r
Utilizing synergetic effects of different fillers is an important strategy to design and develop high-performance nanocomposites. However, owing to the well-known problems such as dispersion, solution viscosity control, and so on, synergetic enhancement effects are usually offset by the defects induced by fillers in highly loaded nanocomposites. In this work, remarkable synergetic efficiency was realized in graphene nanoplatelet (GNP) and multiwalled carbon nanotube (CNT) highly loaded epoxy composites through a well-designed fabrication method. Dramatic thermal conductivity enhancement was observed in the epoxy composites with 10–50 vol% nanocarbon filler due to synergetic effects. For example, the composite with 20 vol% CNTs and 20 vol% GNPs possess a thermal conductivity up to 6.31 W/mK. This is even much higher than that of the composites with individual 50 vol % CNTs or 50 vol% GNPs. A maximum thermal conductivity 7.30 W/mK was obtained, which is 38-fold of that of the pure epoxy resin. Thermal transport channels in the composites were thoroughly analyzed, and the mechanism of high synergetic effects achieved in thermal conductivity enhancement was discussed from the viewpoints of intrinsic properties, dispersion, contact, and matrix interaction of the fillers.
Co-reporter:Jinhong Yu, Xingyi Huang, Chao Wu, Xinfeng Wu, Genlin Wang, Pingkai Jiang
Polymer 2012 Volume 53(Issue 2) pp:471-480
Publication Date(Web):24 January 2012
DOI:10.1016/j.polymer.2011.12.040
Interface is a critical factor in determining the properties of polymer composites. Generally, the physicochemical properties of the interface are closely associated with the surface chemistry of fillers. In this study, we report a simple method to fabricate boron nitride (BN) nanoplatelets using a sonication-centrifugation technique and investigate the effects of functionalization BN nanoplatelets on thermal properties of epoxy composites. Two methods have been used for functionalizing BN nanoplatelets: non-covalent functionalization by octadecylamine (ODA) and covalent functionalization by hyperbranched aromatic polyamide (HBP). The functionalized BN nanoplatelets were characterized by Fourier-transform infrared (FT-IR), nuclear magnetic resonance (1H NMR), thermogravimetric analyzer (TGA), and transmission electron microscopy (TEM). Epoxy composites were fabricated by incorporating three kinds of fillers: BN nanoplatelets, BN nanoplatelets functionalized by ODA (BN-ODA), and BN nanoplatelets functionalized by HBP (BN-HBP). Our results show that the BN-HBP results in a strong interface and thus the composites exhibit significantly increased glass transition temperature, thermal decomposition temperature, thermal conductivity and dynamic thermal mechanical modulus. BN-ODA produced intermediate interface interaction, resulting in a moderate improvement of thermal properties. The composites with BN nanoplatelets show the least improvements of thermal properties.
Co-reporter:Jinhong Yu;Ruimei Huo;Chao Wu;Xinfeng Wu;Genglin Wang
Macromolecular Research 2012 Volume 20( Issue 8) pp:816-826
Publication Date(Web):2012 August
DOI:10.1007/s13233-012-0122-2
Co-reporter:Chao Wu, Xingyi Huang, Liyuan Xie, Xingfeng Wu, Jinghong Yu and Pingkai Jiang
Journal of Materials Chemistry A 2011 vol. 21(Issue 44) pp:17729-17736
Publication Date(Web):06 Oct 2011
DOI:10.1039/C1JM12903A
High permittivity polymer-based materials are highly desirable due to their inherent advantages of being easy to process, flexible and light weight. Herein, a new strategy for the development of polymer composites with high permittivity and low dielectric loss has been proposed based on morphology-controllable graphene–TiO2 nanorod hybrid nanostructures. These hybrid nanostructures possess large aspect ratio, high surface area and high electric conductivity graphene sheets, which provide ideal electrodes in the construction of microcapacitors. In addition, the morphology-controllable TiO2 nanorod decoration effectively prevents direct contact between the graphene sheets in the composite, which give advantages for forming a large microcapacitor network and suppressing the leakage current. As a consequence, a polystyrene composite with 10.9 vol% graphene–TiO2 nanorod sheets exhibits a very high permittivity of 1741 at 102 Hz, which is 643 times higher than the value for pure polystyrene (2.7), and low dielectric loss (tanα) of only 0.39. The permittivity of the composites can be controlled by controlling the amount of nanorod decoration on the graphene substrates, which provides a new pathway for tuning the permittivity of polymer composites. We expect that our strategy of controlling filler interface will be applied to acquire more polymer composites with high permittivity and low dielectric loss.
Co-reporter:Liyuan Xie, Xingyi Huang, Chao Wu and Pingkai Jiang
Journal of Materials Chemistry A 2011 vol. 21(Issue 16) pp:5897-5906
Publication Date(Web):23 Mar 2011
DOI:10.1039/C0JM04574H
Core-shell structured BaTiO3/poly(methyl methacrylate) (PMMA) nanocomposites were successfully prepared by in situ atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) from the surface of BaTiO3 nanoparticles. A broadband dielectric spectrometer was used to investigate the temperature dependence of the dielectric properties of the nanocomposites in a frequency range from 0.1 Hz to 1 MHz. It was found that the nanocomposites not only showed a significantly increased dielectric constant when compared with pure PMMA, but also showed the inherent low loss of the base polymer in a wide range of frequencies. Only in the very low frequency/high temperature range, can a higher dielectric loss can be observed in the nanocomposites. It was also found that the effective dielectric constant of the core-shell structured hybrid nanoparticles can be tailored by varying the polymer shell thickness. The dielectric response of beta relaxation of PMMA was also studied and the results showed that the nanoparticles had no influence upon the relaxation activation energy. Fourier-transform infrared spectroscopy (FTIR) and 1H NMR spectra confirmed the chemical structure of the PMMA shell on the surface of the BaTiO3 nanoparticles. Transmission electron microscopy (TEM) and thermogravimetric analysis (TGA) results revealed that the PMMA shell thickness could be well controlled by tuning the feed ratio of MMA to BaTiO3.
Co-reporter:Yong Li, Xingyi Huang, Zhiwei Hu, Pingkai Jiang, Shengtao Li, and Toshikatsu Tanaka
ACS Applied Materials & Interfaces 2011 Volume 3(Issue 11) pp:4396
Publication Date(Web):October 18, 2011
DOI:10.1021/am2010459
Dielectric polymer composites with high dielectric constants and high thermal conductivity have many potential applications in modern electronic and electrical industry. In this study, three-phase composites comprising poly(vinylidene fluoride) (PVDF), barium titanate (BT) nanoparticles, and β-silicon carbide (β-SiC) whiskers were prepared. The superiority of this method is that, when compared with the two-phase PVDF/BT composites, three-phase composites not only show significantly increased dielectric constants but also have higher thermal conductivity. Our results show that the addition of 17.5 vol % β-SiC whiskers increases the dielectric constants of PVDF/BT nanocomposites from 39 to 325 at 1000 Hz, while the addition of 20.0 vol % β-SiC whiskers increases the thermal conductivity of PVDF/BT nanocomposites from 1.05 to 1.68 W m–1 K–1 at 25 °C. PVDF/β-SiC composites were also prepared for comparative research. It was found that PVDF/BT/β-SiC composites show much higher dielectric constants in comparison with the PVDF/β-SiC composites within 17.5 vol % β-SiC. The PVDF/β-SiC composites show dielectric constants comparable to those of the three-phase composites only when the β-SiC volume fraction is 20.0%, whereas the dielectric loss of the PVDF/β-SiC composites was much higher than that of the three-phase composites. The frequency dependence of the dielectric property for the composites was investigated by using broad-band (10–2–106 Hz) dielectric spectroscopy.Keywords: barium titanate (BaTiO3) nanoparticles; dielectric constant; poly(vinylidene fluoride) (PVDF); silicon carbide (β-SiC) whiskers; thermal conductivity;
Co-reporter:Jinhong Yu, Xingyi Huang, Lichun Wang, Peng Peng, Chao Wu, Xinfeng Wu and Pingkai Jiang
Polymer Chemistry 2011 vol. 2(Issue 6) pp:1380-1388
Publication Date(Web):02 Apr 2011
DOI:10.1039/C1PY00096A
Epoxy nanocomposites with hyperbranched aromatic polyamide grafted alumina (Al2O3) nanoparticles as inclusions were prepared and their thermal properties were studied. The Al2O3 nanoparticles were firstly treated with a silane coupling agent to introduce amine groups, then grafting of the hyperbranched aromatic polyamide started from the modified surface. Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy (NMR) analysis proved hyperbranched aromatic polyamide grafted Al2O3 nanoparticles were successfully prepared by solution polymerization. Transmission electron microscopy (TEM) showed that there was a thin polymer layer on the Al2O3 nanoparticles surface, which contributes to the uniform dispersion of Al2O3 nanoparticles in epoxy matrix and the improvement of the interfacial interaction between Al2O3 nanoparticles and epoxy matrix. Thus the glass transition temperature, thermal stability, thermal conductivity and thermomechanical properties of nanocomposites were enhanced.
Co-reporter:Jinhong Yu;Chao Wu;Lichun Wang ;Xinfeng Wu
Polymer Composites 2011 Volume 32( Issue 10) pp:1483-1491
Publication Date(Web):
DOI:10.1002/pc.21106
Abstract
A nanocomposite of Poly(vinylidene fluoride) (PVDF) was prepared with graphene sheets (GSs), which are a novel filler by a solution method. The structure-properties relationships of PVDF/GSs nanocomposites were studied. The results of differential scanning calorimetry and X-ray diffraction show that addition of GSs to the PVDF matrix promotes an α phase to β phase transformation of the polymer crystal. The nanocomposites exhibit significant increases in dynamic mechanical properties and thermal stability compared to the neat PVDF. In addition, the incorporation of GSs in PVDF indicated excellent optical transparency at the lowest weight fractions of GSs and modified wettability of PVDF. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers
Co-reporter:Lichun Wang;Genlin Wang
Journal of Applied Polymer Science 2011 Volume 120( Issue 1) pp:368-378
Publication Date(Web):
DOI:10.1002/app.33149
Abstract
The halogen-free flame retardant (HFFR) ethylene-vinyl acetate copolymer (EVM)/ATH/SiO2 composites have been prepared by melting compounding method, and the flame retardant, thermal stability, rheological, electrical, and mechanical properties have been investigated by cone calorimeter, LOI, UL-94, TG, FE-SEM, rotational rheometer, dielectric breakdown, and ultimate tensile. The results indicate that the flame retardant of EVM vulcanizates is improved and the fire jeopardizing is dramatically reduced due to the addition of ATH. It is necessary that sufficient loading of ATH (≥120 phr) is needed to reach essential level (LOI > 30; V-0 rating) of flame retardant for HFFR EVM/ATH/SiO2 composites used as cable in industry. The rheological characteristics show that at all the measurement frequencies, the storage and loss modulus of the composites increase monotonously as the concentration of ATH filler increases, while the complex viscosity and tan delta present reverse trend. And also, it has been found that the HFFR composites at high filler concentrations still keep good mechanical and electrical properties, which is very important for practical applications as cable. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Co-reporter:Lichun Wang;Xinfeng Wu;Chao Wu;Jinhong Yu;Genlin Wang
Journal of Applied Polymer Science 2011 Volume 121( Issue 1) pp:68-77
Publication Date(Web):
DOI:10.1002/app.33226
Abstract
A novel phosphorus-silicon-containing flame retardant, spirocyclic pentaerythritol bisphosphorate disphosphoryl chloride/9, 10-dihydro-9-oxa-10-phosphaphanthrene-10-oxide/vinyl methyl dimethoxysilane (SPDV), was synthesized successfully and used for optimizing the flame retardancy of ethylene-vinyl acetate copolymer (EVM) rubber/magnesium hydroxide (MDH) composites. The microstructure of SPDV was characterized and determined by Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy. Thermogravimetric analysis (TGA) showed that SPDV had good charring effect in air even at high temperature (800°C). The flame retardancy of the optimized EVM/MDH composites by SPDV was investigated by limiting oxygen index (LOI), cone calorimeter, and UL-94 vertical burning tests. A higher LOI value (29.4%) and better UL-94 rating (V-0) can be achieved for the optimized EVM/MDH composite (EVM-7) than EVM/MDH composite without SPDV (EVM-3) with the total loading of additives. The HRR decreased and residual mass increased gradually as the loading of SPDV increased for the optimized EVM/MDH composites. There existed distinct synergistic intumescent flame-retardant effect between SPDV and MDH in EVM matrix. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Co-reporter:Lichun Wang;Ping Kai Jiang
Journal of Applied Polymer Science 2011 Volume 119( Issue 5) pp:2974-2983
Publication Date(Web):
DOI:10.1002/app.33028
Abstract
The synthesized flame retardant 9,10-dihydro-9-oxa-10-phosphaphanthrene-10-oxide/vinyl methyl dimethoxysilane (DV) was used to modify multiwalled carbon nanotubes (MWNTs). The results of FTIR, 1H-NMR, and TGA measurements show that DV has been covalently grafted onto the surfaces of MWNTs, and the MWNTs-g-DV is obtained successfully. Transmission electron microscopy images show that a core-shell nanostructure appears with MWNTs as the core and the DV thin layers as the shell, and the modified MWNTs with DV can achieve better dispersion than unmodified MWNTs in EVM matrix. Thermogravimetric analysis and cone calorimeter tests indicate that the thermal stability and flame retardant are improved for the presence of the MWNTs in EVM matrix. Moreover, the improvement is more evident for EVM/MWNTs-g-DV composite compared to unmodified MWNTs-based composite, which can be attributed to the better dispersion of the DV-modified MWNTs and to the chemical structure of the combustion residue. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Co-reporter:Zhishen Ma, Xingyi Huang, Pingkai Jiang
Polymer Degradation and Stability 2010 Volume 95(Issue 9) pp:1943-1949
Publication Date(Web):September 2010
DOI:10.1016/j.polymdegradstab.2010.04.002
In this work, we investigated the effects of an ethylene propylene diene monomer (EPDM) and poly[styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS) on the water tree resistance in cross-linked polyethylene (XLPE). The XLPE/EPDM and XLPE/SEBS blend samples were prepared by melting compounding and subsequent compression molding. It was found that SEBS could greatly increase the water tree resistance of XLPE and the resistance performance was improved with SEBS content within 15 phr, whereas EPDM did not show any improvement in the water tree resistance of XLPE. The frequency dependent behaviors of the water treeing phenomena and the effects of EVA on the water tree resistance of XLPE/EPDM and XLPE/SEBS blends were also investigated. The water treeing phenomena of the blends were interpreted from the viewpoints of electro-mechanical and electro-chemical mechanisms.
Co-reporter:Jingkuan Duan;Chonung Kim
Polymer Composites 2010 Volume 31( Issue 2) pp:347-358
Publication Date(Web):
DOI:10.1002/pc.20812
Abstract
The alignment of multiwalled carbon nanotubes (MWCNTs) and thermosetting resins in nanocomposites based on field-aided micro-tailoring (FAiMTa) technology was studied by means of scanning electric microscopy (SEM), Raman spectroscopy, and atomic force microscopy (AFM), and the effect of the different values of electric field intensity on the changes of the microstructures and properties of nanocomposites were presented. The experimental results implied that the electric field encouraged the molecular alignment of polymers and MWCNTs orientation within the polymeric matrices along the field direction during their curing stages. It was found that the extents of their orientation and alignment were closely dependent on the external electric field intensity by means of Raman spectroscopy and AFM measurements. The thermal and dielectric properties of nanocomposites were examined by thermogravimetric analysis (TGA) and dielectric analysis (DEA), respectively. The TGA and DEA measurements revealed substantial differences in the thermal and dielectric behaviors for the thermoelectrically processed nanocomposites. These differences could be ascribed to the microstructural changes of matrix at the molecular level and the alignment of nanofillers. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers
Co-reporter:Zhisen Ma;Lichun Wang ;Junsheng Yang
Journal of Applied Polymer Science 2010 Volume 118( Issue 4) pp:2350-2357
Publication Date(Web):
DOI:10.1002/app.32068
Abstract
In this study, we investigated the effect of an aromatic polymer, styrene–ethylene–butadiene–styrene (SEBS), on the water-tree resistance of crosslinked polyethylene (XLPE), and the synergetic effect of SEBS and ethylene vinyl acetate (EVA) was also investigated. The XLPE/SEBS and XLPE/SEBS/EVA samples were characterized by means of differential scanning calorimetry, scanning electron microscopy, mechanical measurements, and an accelerated water-treeing experiment, and the obtained results clearly show the relevant influence of SEBS and EVA, and as expected, the addition of SEBS and EVA was found to synergistically influence the water-tree resistance of XLPE more positively in comparison with that without the addition of EVA. In addition, it also indicated that the blends possessed excellent dielectric behaviors, such as the dielectric constant and dissipation factor. The crystallization of the blends decreased with increasing SEBS content and addition of EVA. However, the melting temperature of the blends increased with the addition of SEBS and EVA, but the melting temperature of the blends decreased with increasing SEBS content. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Co-reporter:Zhi-sen Ma;Xing-yi Huang;Jun-sheng Yang
Chinese Journal of Polymer Science 2010 Volume 28( Issue 1) pp:
Publication Date(Web):2010 January
DOI:10.1007/s10118-010-8191-1
The synergetic influence of silane-grafting and polar additives (EVA) on the water tree resistance of the low density polyethylene has been investigated. A series of samples obtained before and after hydration have been characterized by measuring gel content, infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and dielectric measurements. The results obtained clearly show that the silane condensation occurred and that the silane-grafting and polar additives have synergetic effects on the water tree resistance of LDPE with little influence on its dielectric properties, e.g. the dielectric breakdown strength, dielectric permittivity and loss tangent.
Co-reporter:Lichun Wang;Jinhong Yu;Zongliu Tang
Journal of Materials Science 2010 Volume 45( Issue 24) pp:6668-6676
Publication Date(Web):2010 December
DOI:10.1007/s10853-010-4759-y
A novel flame retardant containing phosphorus–silicon, spirocyclic pentaerythritol bisphosphorate disphosphorylchloride/9,10-dihydro-9-oxa-10-phosphaphanthrene-10-oxide/vinyl methyl dimethoxysilane (SPDV), has been used to modify multiwalled carbon nanotubes (MWNTs) and the m-MWNTs (MWNTs-g-SPDV) was obtained by the covalent grafting of SPDV onto the surfaces of MWNTs. And then the according poly(ethylene-co-vinyl acetate) nanocomposites were prepared via melt blending. Transmission electron microscopy (TEM) results showed that a core–shell nanostructure with MWNTs as the hard core and SPDV as the soft shell was formed, and the resultant m-MWNTs can achieve better dispersion than pristine MWNTs in EVM matrix. Cone calorimeter results showed that better flame retardancy was obtained for EVM/m-MWNTs nanocomposites. Mechanical measurements showed that the Young’s modulus increases due to the presence of MWNTs or m-MWNTs. The flammability and mechanical properties of the nanocomposites are strongly dependent on the dispersion state of nanotubes.
Co-reporter:Lichun Wang;Junqing Jiang;Jinhong Yu
Journal of Polymer Research 2010 Volume 17( Issue 6) pp:891-902
Publication Date(Web):2010 November
DOI:10.1007/s10965-009-9381-9
A novel flame retardant (SPDV) containing phosphorus and silicon elements at the same time was synthesized. Spirocyclic pentaerythritol bisphosphorate disphosphoryl chloride (SPDPC) synthesized through simple dehydrochlorination reaction of pentaerythritol (PER) and phosphorus oxychloride (POCl3) was introduced into 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO)/ vinylmethyldimethoxy silane (VMDMS) oligomer (DV) to form a novel flame retardant. The structure and properties of SPDPC, DV and SPDV were characterized by FT-IR, NMR and TGA. After blended with EVM, the flame retardance of EVM/SPDV composites was estimated by cone calorimeter, limited oxygen index (LOI) and UL-94, and thermal stability was investigated using TGA. The morphological structure of the char formed after combustion in cone calorimeter was investigated by Scanning Electron Microscopy (SEM). The results indicate that the flame retardant and thermal stability were improved by incorporation of SPDV. The rich foamed char layers were observed in the residues after combustion in cone calorimeter test, which exactly benefits the thermal stability and flame retardant of EVM materials.
Co-reporter:Xingyi Huang, Pingkai Jiang, Choung Kim, Fei Liu, Yi Yin
European Polymer Journal 2009 Volume 45(Issue 2) pp:377-386
Publication Date(Web):February 2009
DOI:10.1016/j.eurpolymj.2008.11.018
Poly(vinylidene fluoride) (PVDF)-multiwalled carbon nanotube (MWNT) composites with different aspect ratios of MWNT were prepared by a coagulation method. Field emission scanning electron and transmission electron microscopic studies reveal that MWNT are well dispersed in the PVDF matrix. The X-ray diffraction and differential scanning calorimeter data indicate that the composites with high aspect ratio of MWNT have the ββ phase structure at the MWNT loading level of 2.0wt%, and have a mixture of αα and ββ phase below 2wt% MWNT, and that those composites with low aspect ratio of MWNT, however, always have a mixture of αα and ββ phase for MWNT concentrations ⩽2.0wt%. The dielectric constant values increase with the increase in MWNT loading level and the percent increase in dielectric constant is much greater in the composite filled with high aspect ratio of MWNT than in that loaded with low aspect ratio. And also, it has been found that the dielectric loss of the composites with MWNT loading level ⩽2.0wt% is still as low as neat PVDF, which is of significance for dielectric application.
Co-reporter:Xingyi Huang, Liyuan Xie, Pingkai Jiang, Genlin Wang, Yi Yin
European Polymer Journal 2009 Volume 45(Issue 8) pp:2172-2183
Publication Date(Web):August 2009
DOI:10.1016/j.eurpolymj.2009.05.019
This paper presents the results of morphological and ac electrical investigations on low density polyethylene (LDPE) composites with octavinyl polyhedral oligomeric silsesquioxane (POSS). It has been shown that at low loadings, the frequency dependence of dielectric constant and dielectric loss for the LDPE/POSS composites showed unusual behaviors when compared with conventional (micro-sized particulates) composites. The ac breakdown strength was measured and statistical analysis was applied to the results to determine the effects of POSS loadings on the dielectric strength of LDPE. The morphological characterization showed that the presence of POSS additives apparently altered the supermolecular structure of LDPE and resulted in more homogeneous morphology when compared with the neat LDPE. The structure–property relationship was discussed and it was concluded that the final dielectric properties of the composites were determined not only by the incorporation of POSS additives but also by the supermolecular structure of LDPE. Rheological analyses of LDPE/POSS composite were also performed and the results showed that the octavinyl-POSS had good compatibility with LDPE.
Co-reporter:Xingyi Huang;Zhisen Ma;Yaqun Wang;Yi Yin;Zhe Li
Journal of Applied Polymer Science 2009 Volume 113( Issue 6) pp:3577-3584
Publication Date(Web):
DOI:10.1002/app.30313
Abstract
The effect of the surface modification with a silane coupling agent (octyl-trimethoxysilane) of aluminum (Al) nanoparticles on the dielectric breakdown behaviors of polyethylene (PE)/Al nanocomposites was investigated in comparison of the influence of the improvement of the interfacial adhesion between Al nanoparticles and PE using a compatibilizer (maleic anhydride grafted polyethylene). It was found that when compared with the other modification approaches, the surface-treated Al nanofiller with the silane coupling agent makes it possible for the PE/Al nanocomposites to still keep the relatively higher breakdown strength even in the higher Al loading level above 14 vol %, which can be understood in terms of the better interfacial adhesion between the surface-treated particle dispersion and the matrix. The combined effects of the Al nanoparticles on the different factors which influence the dielectric breakdown processes in polymer matrix such as microstructure, conductivity, and crystallinity of the nanocomposites were discussed in detail. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Co-reporter:Jingkuan Duan;Chonung Kim
Journal of Polymer Research 2009 Volume 16( Issue 1) pp:45-54
Publication Date(Web):2009 January
DOI:10.1007/s10965-008-9201-7
The novel interpenetrating polymer networks (IPNs) based on cycloaliphatic epoxy resin (CER) containing cyclohexene oxide groups and tri-functional acrylate, trimethylol-1, 1, 1-propane trimethacrylate (TMPTMA) were synthesized. The formation of the IPNs was on-line monitored by means of polarizing optical microscope, time-resolved light scattering and Fourier transform infrared spectroscopy. The morphological and mechanical properties of the resultant IPNs were investigated and evaluated with scanning electron microscopy (SEM) and dynamical thermal mechanical analysis (DTMA), respectively. The on-line monitoring results showed that during the course of the IPNs formation, the TMPTMA component was cured more quickly than the CER component, leading to the formation of the sequential IPNs. During the early curing stage, there were the phase separation phenomena in the CER/TMPTMA system. The SEM results revealed that although there were some slight phase separation phenomena in the CER/TMPTMA system in the early curing stage, the resultant IPNs displayed the homogeneous structures and did not show the apparent phase separation morphology. The DTMA results revealed that the resulting IPNs exhibited rather higher modulus and denser cross-linking network structure than the neat CER system.
Co-reporter:Xingyi Huang, Pingkai Jiang, Chonung Kim, Qingquan Ke, Genlin Wang
Composites Science and Technology 2008 Volume 68(Issue 9) pp:2134-2140
Publication Date(Web):July 2008
DOI:10.1016/j.compscitech.2008.03.009
Linear low density polyethylene (PE) aluminum (Al) nanocomposites were prepared and their morphology and properties were investigated. The particular attention was given to the structure/property relationship of the nanocomposites and an equivalent electric circuit model was proposed to interpret the dependences of the dielectric behaviors of the PE/Al nanocomposites on the nanoparticle concentration and the measuring frequency. The increase of the dielectric constant shows the effectiveness of Al nanoparticles in altering the intrinsic dielectric properties of PE. The microstructure transition revealed by morphological investigations has been also verified at the same composition as that from the rheological data. And also, it has been found that the nanocomposites at high filler concentrations still keep good mechanical properties and breakdown strength, which is very important for practical applications.
Co-reporter:Jingkuan Duan;Chonung Kim;Zheng Yun
Journal of Applied Polymer Science 2008 Volume 110( Issue 5) pp:3096-3106
Publication Date(Web):
DOI:10.1002/app.28835
Abstract
Vacuum pressure impregnation has been known as the most advanced impregnation technology that has ever been developed for large and medium high-voltage electric machines and apparatuses. We developed one new type of vacuum-pressure-impregnation resin with excellent properties by means of a novel approach based on in situ sequential interpenetrating polymer networks resulting from the curing of trimethacrylate monomer [trimethylol-1,1,1-propane trimethacrylate (TMPTMA)] and cycloaliphatic epoxy resin (CER). In this study, the influence of the concentrations of the components and their microstructures on their thermal and dielectric behaviors were investigated for the cured CER/TMPTMA systems via atomic force microscopy, dynamic mechanical analysis, thermogravimetric analysis, and dielectric analysis. The investigation results show that the addition of TMPTMA to the CER–anhydride system resulted in the formation of a uniform and compact microstructure in the cured epoxy system. This led the cured CER/TMPTMA systems to show much higher moduli in comparison with the pure CER–anhydride system. The thermogravimetric analysis results show that there existed a decreasing tendency in the maximum thermal decomposition rates of the cured CER/TMPTMA systems, which implies that the thermal stability properties improved to some extent. The dielectric analysis results show that the cured CER/TMPTMA systems displayed quite different dielectric behaviors in the wide frequency range 0.01 Hz–1 MHz and in the wide temperature range 27–250°C compared with the cured CER–anhydride system. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Co-reporter:Xingyi Huang;Chonung Kim;Jingkuan Duan;Genlin Wang
Journal of Applied Polymer Science 2008 Volume 107( Issue 4) pp:2494-2499
Publication Date(Web):
DOI:10.1002/app.27357
Abstract
Spherulites are important morphological forms in semicrystalline polymers. Polarized optical microscope (POM) is a powerful tool for observing the spherulite morphology of semicrystalline polymers and their composites, but it can not resolve spherulites with average size smaller than 5 μm and also not be used to study the opaque nanocomposites film samples. Atomic force microscopy (AFM) is an excellent tool for observing spherulites comparatively small in size and not restricted by the transparency of the samples. In this work, AFM was used to investigate the impact of Al nano- and microparticles on spherulitic textures, lamellar thickness, and thickness distribution of low density polyethylene (LDPE). It was found that the spherulitic texture was seriously disordered by the nanoparticles, and that the LDPE in nanocomposites was found only to have poorly developed spherulite structure. The incorporation of microparticles can facilitate the growth of the lamellae but decrease the size of the spherulites. Furthermore, the lamellar thickness and its distribution did not alter so much with the addition of nano- and microparticles. Wide-angle X-ray diffraction (WXRD) was used to determine the crystal structure of LDPE, and the results show that both Al nanoparticles and microparticles do not change the unit cell parameters. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Co-reporter:Chonung Kim, Zhijian Jin, Xingyi Huang, Pingkai Jiang, Qingquan Ke
Polymer Degradation and Stability 2007 Volume 92(Issue 4) pp:537-544
Publication Date(Web):April 2007
DOI:10.1016/j.polymdegradstab.2007.01.020
The power cable insulation is in permanence subjected to thermal aging during its operating service. Thermal aging may influence not only the electrical, physicochemical and other properties of the XLPE cable insulation, but also the initiation and propagation of water tree inside it. Our research on the influence of thermal degradation to the water treeing behavior of XLPE cable insulation shows that thermal oxidation is the most influential to the initiation and growth of water treeing from the surface of XLPE cable insulation among all the probable factors caused during thermal aging.
Co-reporter:Chonung Kim, Jongbok Jang, Xingyi Huang, Pingkai Jiang, Hyeil Kim
Polymer Testing 2007 Volume 26(Issue 4) pp:482-488
Publication Date(Web):June 2007
DOI:10.1016/j.polymertesting.2007.01.003
Water trees are localized degraded zones that can be found in the polymeric insulation of service-aged underground cables, and observed as microchannels or chains of microcavities in the bulk of a solid dielectric material. Since water trees have microscale local structures, some phenomena related to them can be understood and analyzed in detail only when using numerical analysis methods such as finite element method (FEM). For the artificial accelerated growth of water trees, water electrodes in needle form or with conical structure are often utilized, and then some unexpected initiation positions and shapes of water trees have frequently been observed. This paper deals with the investigation of the influence of the geometrical configuration of water electrodes on water tree initiation and its shape, on the basis of numerical experiment results using the FEM and accelerated water treeing test data.
Co-reporter:Qingquan Ke;Xingyi Huang;Ping Wei;Genlin Wang
Journal of Applied Polymer Science 2007 Volume 103(Issue 6) pp:3483-3490
Publication Date(Web):5 DEC 2006
DOI:10.1002/app.24467
Most premature failure of underground crosslinked polyethylene (XLPE) cables in service, a matter of great concern, is due to aging induced by water treeing. To improve the water-tree resistance, sodium-neutralized poly (ethylene-co-acrylic acid) (EAA–Na) ionomers were blended with XLPE; the EAA–Na ionomers were prepared through the neutralization of sodium hydroxide and poly(ethylene-co-acrylic acid). A series of XLPE/EAA–Na ionomer blends were investigated through the measurement of the water absorption ratio, water treeing, and mechanical and dielectric testing; the results strongly suggested that EAA–Na ionomers could improve the water-tree resistance of XLPE, and the XLPE/EAA–Na blends retained excellent mechanical properties and dielectric properties. Moreover, through the characterization of XLPE/EAA–Na blends with Fourier transform infrared spectrometry, dynamic mechanical analysis, and scanning electron microscopy, it was found that the neutralization reaction could be achieved completely; the XLPE and EAA–Na ionomers were partially compatible, so the EAA–Na ionomers could be dispersed well in the matrix with the process examined in this study. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3483–3490, 2007
Co-reporter:Qing Quan Ke;Xing Yi Huang;Ping Wei;Gen Lin Wang;Ping Kai Jiang;Qing Quan Ke;Xing Yi Huang;Ping Wei;Gen Lin Wang;Ping Kai Jiang
Journal of Applied Polymer Science 2007 Volume 104(Issue 3) pp:1920-1927
Publication Date(Web):26 FEB 2007
DOI:10.1002/app.25874
Crosslinked linear low density polyethylene (XLPE) containing polyolefin elastomers (POE) has been evaluated. The blends with different dicumyl peroxide (DCP) and POE contents have been prepared and processed by compression molding. A series of the samples obtained have been investigated by gel content determination, scanning electron microscopy (SEM), different scanning calorimetry (DSC), mechanical, and dielectric behaviors measurements. The results obtained clearly show the relevant influence of the POE content, as well as of the DCP content, which tends to enhance crosslinking. As expected, the toughness of XLPE is improved by using adequate content of POE, and the blends exhibit a much more similar tensile behavior to that of elastomer. In addition, the results indicate that the blends possess the excellent dielectric behaviors, such as dielectric constant and dissipation factor. The crystallinity of the blends decreases as the DCP and POE contents increase. The melting temperature of the blends also decreases with the increase of DCP content, while POE content has few influences on the melting temperature of the blends. The SEM images strongly reveal that the blends are partially compatible, and the POE can be dispersed well in the matrix. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1920–1927, 2007
Co-reporter:Xingyi Huang;Qingquan Ke;Chonung Kim;Hanfang Zhong;Ping Wei;Genlin Wang;Fei Liu
Polymer Engineering & Science 2007 Volume 47(Issue 7) pp:1052-1061
Publication Date(Web):29 MAY 2007
DOI:10.1002/pen.20784
The nonisothermal crystallization and melting behavior of LDPE and LDPE/Al nano- and microcomposites prepared from melt compounding were studied using differential scanning calorimetry (DSC). The DSC results show that the Al nanoparticles can either facilitate or hinder the crystallization of LDPE, depending on the dispersion of the nanoparticles in LDPE. The well-dispersed Al nanoparticles do not have nucleating effects and mainly act as obstacles in the crystallization process, but the agglomerates of Al nanoparticles can act as nucleating agents and slightly accelerate the crystallization process of LDPE. The Al microparticles have nucleating effect and facilitate the crystallization process of LDPE. The combined Avrami–Ozawa equation was used to describe the nonisothermal crystallization process. It was found that the combined Avrami–Ozawa method can successfully describe the nonisothermal crystallization process. The melting behavior indicates that the lamellar thickness distribution of the nanocomposites and microcomposites is not significantly changed in comparison with the neat LDPE. POLYM. ENG. SCI., 47:1052–1061, 2007. © 2007 Society of Plastics Engineers
Co-reporter:Hanfang Zhong;Ping Wei;Dan Wu;Genlin Wang
Journal of Polymer Science Part B: Polymer Physics 2007 Volume 45(Issue 13) pp:1542-1551
Publication Date(Web):17 MAY 2007
DOI:10.1002/polb.21151
Novel halogen-free compounds [9,10-dihydro-9-oxa-10-phosphaphanthrene-10-oxide/vinyl methyl dimethoxysilane/N-β-(aminoethyl)-γ-aminopropyl methyl dimethoxysilane (DOPO–VMDMS–NMDMS)] that simultaneously contain phosphorus, nitrogen, and silicon have been synthesized through the reaction of 9,10-dihydro-9-oxa-10-phosphaphanthrene-10-oxide (DOPO), vinyl methyl dimethoxysilane (VMDMS), and N-β-(aminoethyl)-γ-aminopropyl methyl dimethoxysilane (NMDMS). The chemical structure and properties of DOPO–VMDMS–NMDMS have been investigated with Fourier transform infrared spectroscopy, proton nuclear magnetic resonance, phosphorous nuclear magnetic resonance, and thermogravimetric analysis (TGA). These synthesized flame retardants have been blended with a poly[2,2-propane-(bisphenol) carbonate]/acrylonitrile butadiene styrene (PC/ABS) alloy. The flame-retardant properties of these mixture samples have been estimated with the limiting oxygen index (LOI), and the thermal stability has been characterized with TGA. The LOI value of PC/ABS/DOPO–VMDMS–NMDMS is enhanced up to 27.2 vol % from 21.2 vol %, and the char yield is also improved slightly (from 12 to 17%) with 2.8 wt % phosphorus, 3.0 wt % silicon, and 0.5 wt % nitrogen (at a 30 wt % loading of DOPO–VMDMS–NMDMS). The results show that there is a synergistic effect of the elements phosphorus, silicon, and nitrogen on the flame retardance. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1542–1551, 2007
Co-reporter:Zhanipai Su;Qiang Li;Ping Wei
Journal of Applied Polymer Science 2006 Volume 102(Issue 1) pp:295-302
Publication Date(Web):28 JUL 2006
DOI:10.1002/app.23781
PP was endowed with excellent flame retardant properties by great mount of Mg(OH)2 particulates. It was found that the mechanical properties of PP was severely deteriorated, caused by the bad compatibility between filler and matrix, as well as the agglomerate of Mg(OH)2 particles in PP matrix. The addition of rubbery phase as the third component could remarkably improve the Izod impact strength of PP highly filled inorganic flame retardant agent. In this article, EPDM and sulfated EPDM ionomer were adopted as the third component to improve the mechanical properties of PP/Mg(OH)2 composites. The composites have better mechanical properties using sulfated EPDM ionomer as the third component than that of neat EPDM. The theoretical analysis and SEM photographs showed that even dispersion of particulates and the less domain size of rubbery phases as well as the better adhesion between rubbery phase and PP matrix were the main reasons for the improvement of the mechanical properties. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 295–302, 2006
Co-reporter:Chonung Kim;Tao He;Ping Wei;Xingyi Huang;Zhijian Jin
Polymer Engineering & Science 2006 Volume 46(Issue 12) pp:1721-1727
Publication Date(Web):13 NOV 2006
DOI:10.1002/pen.20621
The influence of γ irradiation on the dielectric and physicochemical properties of polyethylene-octene elastomer (POE) containing 120 phr aluminum hydroxide (Al(OH)3) as fillers has been investigated. The dielectric properties of the γ-irradiated POE highly filled with Al(OH)3 have been measured over a wide range of frequencies (70 kHz–3 MHz). It was found that γ irradiation strongly influences the dielectric properties of the POE composite in the dose range 0–250 kGy. POLYM. ENG. SCI. 46:1721–1727, 2006. © 2006 Society of Plastics Engineers
Co-reporter:Pingkai Jiang;Qiang Li;Ping Wei
Macromolecular Materials and Engineering 2005 Volume 290(Issue 9) pp:912-919
Publication Date(Web):31 AUG 2005
DOI:10.1002/mame.200500109
Summary: A novel intumescent flame retardant (PSiNII), containing silicon, phosphorus and nitrogen, has been synthesized and incorporated into poly(propylene) (PP). The flame retardancy of PP/PSiNII, evaluated by the limiting oxygen index (LOI) value, can be enhanced up to 29.5 vol.-% from 17.4 vol.-% with 20% total loading amount of PSiNII. The thermal degradation behavior of PP/PSiNII are investigated by thermogravimetric analysis (TGA) under nitrogen and air, and pressure differential scanning calorimetry (PDSC) under 1.5 MPa of oxygen. The PP/PSiNII-3 degrades at 400 °C for different time, and the process is investigated by FTIR which indicates there is PO in the char. The morphologies of char formed at 400 °C for 10 min and after LOI test are investigated by scanning electron microscopy (SEM). The morphological structure of the char exhibits the swollen cells in the inner and a smooth outer surface, which do good to the thermal properties and fire performance of PP. The thermal stability of PP is improved by incorporating PSiNII.
Co-reporter:Qiang Li;Hanfang Zhong;Ping Wei
Journal of Applied Polymer Science 2005 Volume 98(Issue 6) pp:2487-2492
Publication Date(Web):29 SEP 2005
DOI:10.1002/app.21944
The N-[3-(dimethoxy-methyl-silanyl)-propyl]-N′- (9-methyl-3,9-dioxo-2,4,8,10-tetraoxa-3,9-diphospha-spiro[5.5]undec-3-yl)-ethane-1,2-diamine/dimethoxy dimethyl silane copolymer (PSiN II), which simultaneously contains silicon, phosphorus, and nitrogen, is synthesized and incorporated into polypropylene (PP). The flame retardancy is evaluated by the limiting oxygen index value, which is enhanced to 29.5 from 17.4 with 20% total loading of PSiN II. The thermal degradation behavior of PP/PSiN II is investigated by thermogravimetric analysis under N2 and air. The PP/PSiN II sample degrades at 400°C for different amounts of time, and the process of degradation is studied by Fourier transform IR. The morphology of the char formed at 400°C for 10 min is investigated by scanning electron microscopy. The swollen inner structure, close, and smooth outer surface provide a much better barrier for the transfer of heat and mass during fire and good flame retardancy. The thermal stability of PP is improved by incorporation of PSiN II. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2487–2492, 2005
Co-reporter:Qiang Li;Zhanpai Su;Ping Wei;Genglin Wang;Xiaozhen Tang
Journal of Applied Polymer Science 2005 Volume 96(Issue 3) pp:854-860
Publication Date(Web):24 FEB 2005
DOI:10.1002/app.21522
In this study, several flame retardants (FRs), containing phosphorus, nitrogen, and silicon, were synthesized. These synthesized FRs were blended with polypropylene (PP) to obtain mixture samples. The flame-retardant properties of these mixture samples were estimated by the limiting oxygen index (LOI) value and thermal stabilities were characterized by thermogravimetric analysis. The LOI values of these samples were improved from 17.0 to 26.0 and the char yield increased from 0 to 27 wt %. A comparison of these samples, with respect to their LOI values and carbon yield, showed that the FRs, which simultaneously contained phosphorus, nitrogen, and silicon elements, can provide materials with the best flame-retardant properties, suggesting that there is a synergistic effect among the three elements on the flame-retardant properties and char yield when they are used in PP. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 854–860, 2005
Co-reporter:Qiang Li;Ping Wei
Journal of Polymer Science Part B: Polymer Physics 2005 Volume 43(Issue 18) pp:2548-2556
Publication Date(Web):29 JUL 2005
DOI:10.1002/polb.20545
A new intumescent flame retardant (PSiNII), which contains silicon, phosphorus, and nitrogen elements, has been synthesized and incorporated into polypropylene (PP). Its effect on the properties of PP is investigated based on flame retardancy, thermal properties, mechanical properties, and morphologies. The flame retardancy is evaluated by the limiting oxygen index value. The thermal properties (oxidative behaviors and thermal stability) are investigated by thermogravimetric analysis under nitrogen and air atmosphere. The mechanical properties are researched based on the maximum tensile stress and relative strain at break. The morphologies of PP/PSiNII are studied by the scanning electron micrograph. Their flame retardancy and thermal stability are improved by introducing PSiNII. PP/PSiNII blends can achieve high fire performance and keep high mechanical property at the same time. During a fire, the melt-dripping behaviors of PP-containing PSiNII are improved. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2548–2556, 2005
Co-reporter:Chao Wu;Xingyi Huang;Genlin Wang;Xinfeng Wu;Ke Yang;Shengtao Li
Journal of Materials Chemistry A 2012 - vol. 22(Issue 14) pp:
Publication Date(Web):2012/03/13
DOI:10.1039/C2JM16901K
The incorporation of graphene sheets (GSs) into polymer matrices affords engineers an opportunity to synthesize polymer composites with excellent physical performances. However, the development of high performance GS-based composites is difficult because of the easy aggregation of GSs in a polymer matrix as well as the weak interfacial adhesion between GSs and the host polymer. Herein, we present a simple and effective route to hyperbranched aromatic polyamide functionalized graphene sheets (GS–HBA). The resulting GS-HBA exhibits uniform dispersion in a thermoplastic polyurethane (TPU) matrix and strong adhesion with the matrix by hydrogen-bond coupling, which improve the load transfer efficiency from the matrix to the GSs. Thus, the GS–HBA–TPU composites possess excellent mechanical performance and high dielectric performance. It has been demonstrated that the GS–HBA composite has higher modulus, higher tensile strength and higher yield strength, and remains at nearly the same strain at break when compared with the composites with graphene oxide, ethylene diamine-modified graphene, and hydrazine reduced graphene. In addition, the hyperbranched polymer chains allow construction of a large number of microcapacitors and suppress the leakage current by isolating the GSs in a TPU matrix, resulting in a higher permittivity and lower loss tangent for the GS–HBA composite in comparison with ethylene diamine-modified graphene, or hydrazine reduced-graphene composites.
Co-reporter:Liyuan Xie, Xingyi Huang, Chao Wu and Pingkai Jiang
Journal of Materials Chemistry A 2011 - vol. 21(Issue 16) pp:NaN5906-5906
Publication Date(Web):2011/03/23
DOI:10.1039/C0JM04574H
Core-shell structured BaTiO3/poly(methyl methacrylate) (PMMA) nanocomposites were successfully prepared by in situ atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) from the surface of BaTiO3 nanoparticles. A broadband dielectric spectrometer was used to investigate the temperature dependence of the dielectric properties of the nanocomposites in a frequency range from 0.1 Hz to 1 MHz. It was found that the nanocomposites not only showed a significantly increased dielectric constant when compared with pure PMMA, but also showed the inherent low loss of the base polymer in a wide range of frequencies. Only in the very low frequency/high temperature range, can a higher dielectric loss can be observed in the nanocomposites. It was also found that the effective dielectric constant of the core-shell structured hybrid nanoparticles can be tailored by varying the polymer shell thickness. The dielectric response of beta relaxation of PMMA was also studied and the results showed that the nanoparticles had no influence upon the relaxation activation energy. Fourier-transform infrared spectroscopy (FTIR) and 1H NMR spectra confirmed the chemical structure of the PMMA shell on the surface of the BaTiO3 nanoparticles. Transmission electron microscopy (TEM) and thermogravimetric analysis (TGA) results revealed that the PMMA shell thickness could be well controlled by tuning the feed ratio of MMA to BaTiO3.
Co-reporter:Chao Wu, Xingyi Huang, Liyuan Xie, Xingfeng Wu, Jinghong Yu and Pingkai Jiang
Journal of Materials Chemistry A 2011 - vol. 21(Issue 44) pp:NaN17736-17736
Publication Date(Web):2011/10/06
DOI:10.1039/C1JM12903A
High permittivity polymer-based materials are highly desirable due to their inherent advantages of being easy to process, flexible and light weight. Herein, a new strategy for the development of polymer composites with high permittivity and low dielectric loss has been proposed based on morphology-controllable graphene–TiO2 nanorod hybrid nanostructures. These hybrid nanostructures possess large aspect ratio, high surface area and high electric conductivity graphene sheets, which provide ideal electrodes in the construction of microcapacitors. In addition, the morphology-controllable TiO2 nanorod decoration effectively prevents direct contact between the graphene sheets in the composite, which give advantages for forming a large microcapacitor network and suppressing the leakage current. As a consequence, a polystyrene composite with 10.9 vol% graphene–TiO2 nanorod sheets exhibits a very high permittivity of 1741 at 102 Hz, which is 643 times higher than the value for pure polystyrene (2.7), and low dielectric loss (tanα) of only 0.39. The permittivity of the composites can be controlled by controlling the amount of nanorod decoration on the graphene substrates, which provides a new pathway for tuning the permittivity of polymer composites. We expect that our strategy of controlling filler interface will be applied to acquire more polymer composites with high permittivity and low dielectric loss.
Co-reporter:Mi Li, Xingyi Huang, Chao Wu, Haiping Xu, Pingkai Jiang and Toshikatsu Tanaka
Journal of Materials Chemistry A 2012 - vol. 22(Issue 44) pp:NaN23484-23484
Publication Date(Web):2012/10/08
DOI:10.1039/C2JM34683D
Novel polyaniline decorated reduced graphene oxide (rPANI@rGO) two-dimensional (2D) hybrids sheets were successfully prepared by in situ polymerization of aniline on graphene oxide (GO) sheets and successive reduction by hydrazine. PANI is heavily reduced, thus it is electrically insulating. The hybrid sheets were used as a novel filler for high performance poly(methyl methacrylate) (PMMA) nanocomposites. Our results show that, when compared with the PMMA/rGO composites, the PMMA/rPANI@rGO nanocomposites not only show a high dielectric constant but also have low dielectric loss. For example, at 1000 Hz, a dielectric constant of 40 and a dielectric loss of 0.12 were observed in the PMMA/rPANI@rGO nanocomposite with rGO/PMMA volume ratio of 6%, whereas the dielectric constant and dielectric loss of PMMA/rGO composite with rGO/PMMA volume ratio of 6% are about 20 and 1250, respectively. More importantly, the dielectric properties of PMMA/rPANI@rGO nanocomposites can be tuned by controlling the addition of the hybrid sheets. The improved dielectric properties in PMMA/rPANI@rGO nanocomposites should originate from the isolation effect of rPANI on the rGO in PMMA matrix, which not only improves the dispersion of rGO but also hinders the direct electrical contact between rGO. This research sets up a novel route to polymer composites with high dielectric constants and low dielectric loss, and also expands the application space of graphene-based fillers.
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