共查询到20条相似文献，搜索用时 0 毫秒
1.
Thi To Nga Dang S. P. Mahapatra V. Sridhar J. K. Kim K‐J. Kim H. Kwak 《应用聚合物科学杂志》2009,113(3):1690-1700
Dielectric relaxation behavior of multiwalled carbon nanotube reinforced butyl rubber composites has been studied as a function of variation in filler in the frequency range of 20–2 × 106 Hz. The effect of variation in filler loadings on the complex and real parts of impedance was distinctly visible, which has been explained on the basis of interfacial polarization of fillers in a heterogeneous medium and relaxation dynamics of polymer chains in the vicinity of fillers. The electric modulus formalism has been used to further investigate the conductivity and relaxation phenomenon. The frequency dependence of AC conductivity has been investigated by using Percolation theory. The phenomenon of percolation in the composites has been discussed based on the measured changes in electric conductivity and morphology of composites at different concentrations of the filler. The percolation threshold as studied by AC conductivity occurred in the vicinity of 6–8 phr of filler loading. Scanning electron microscope microphotographs showed agglomeration of the filler above this concentration and formation of a continuous network structure. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 相似文献
2.
To investigate the stretching effect of polymer‐based composites, the films of polyvinylidene fluoride (PVDF) and nickel (Ni) composites were stretched at 120°C. It was found there was an abrupt increase in dielectric constants and conductivities with stretching ratio (SR). In comparison to percolation effect caused by involvement of conductive particles, it was named as stretching‐induced percolation here. When SR was near the threshold, dielectric constants showed 17 times improvement and conductivities displayed four to five orders of magnitude enhancement at 100 Hz in low Ni fraction composites. And the reasons of stretching‐induced percolation were analyzed here. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 相似文献
3.
用熔融共混和热压工艺制备了CB/HDPE,MWNT/HDPE聚合物基复合材料,研究了填料体积含量,测试电压,填料形貌尺寸对复合体系介电性能的影响.实验表明,当导电填料含量达到渗流阈值附近时复合材料的介电常数达到最大,测试电压达到一定值时,渗流阈值附近的复合材料介电损耗会迅速增加,相同填料体积含量的MWNT/HDPE复合体系比CB/HDPE体系具有更高的介电常数,利用渗流理论、Maxwell-Wagner界面极化效应和微电容模型解释了实验现象. 相似文献
4.
Meinong Shi Weimin Yang Youchen Zhang Jing Tan Lisheng Cheng Zhiwei Jiao Xiangshi Zhen 《应用聚合物科学杂志》2019,136(42):48131
As one of the duplicated cases of ultrathin polymer films, multilayer graphite/polymer composites are of great interests in various applications. Graphite/polyethylene (PE) composites with various layer numbers and graphite particle sizes were prepared by lamination. The mechanical and dielectric properties and crystalline behavior of the composites were investigated by scanning electron microscopy, differential scanning calorimetry, tensile test, and dielectric strength test. With the same amount of graphite addition, the tensile strength of the composites increases with decreasing layer thickness, but decreases with increasing graphite particle size. The longitudinal tensile strength is greater than the transverse one. The tensile strength of the 36-layer composites with a particle size of 15 μm has enhancements of 34.76 and 68.39% in the longitudinal and transverse directions compared with that of the single-layer pure PE film. The dielectric constant of the composites nonlinearly increases with decreasing layer thickness, while the dielectric loss is independent of this factor. The dielectric constant of the 36-layer composites with a particle size of 15 μm is about two times as large as that of the single-layer pure PE film. The crystalline peak temperature and the crystallinity of the composites increase with the decrease in layer thickness. Coarse-grained molecular dynamics simulations were also carried out to understand the experimental observations by getting an insight into the microstructure of the multilayer composites. This work would be helpful for the production of optimized of multilayer graphite/polymer composites by lamination for electric energy storage. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48131. 相似文献
5.
Bor‐Sen Chiou Andrew R. Lankford Ann E. Mera Dan Zabetakis Paul E. Schoen 《应用聚合物科学杂志》2005,98(1):53-57
The dielectric properties of composites containing copper‐coated tubules in epoxy and polyurethane were characterized and interpreted in terms of contact angle and interfacial tension between the filler and the polymer matrix. The polyurethane samples had larger permittivity values than the epoxy samples over the entire tubule concentration range. The results suggested the tubules in polyurethane were more aggregated than those in epoxy and, consequently, the polyurethane samples were closer to percolation. This was inconsistent with the contact angle and interfacial tension data, because epoxy had larger contact angles and interfacial tension than polyurethane. Therefore, the contact angle and interfacial tension data could not be used to predict tubule distribution in composites. Also, the De Loor model provided a good fit to the permittivity data. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 53–57, 2005 相似文献
6.
Cong Gao Shuling Zhang Yujin Lin Jianxin Mu Zhenhua Jiang 《Polymer International》2015,64(11):1555-1559
The distribution and contents of conductive fillers have a decisive influence on the dielectric properties of polymer/conductive filler composites. Herein, we clarified how the phase morphology and filler contents affect the dielectric properties of poly(ether ether ketone) (PEEK)/polyimide (TPI)/multi‐walled carbon nanotubes (MWCNTs) composites, in which MWCNTs were selectively located in the TPI phase. Firstly, PEEK/TPI/MWCNTs composites with identical MWCNTs content but different PEEK/TPI ratios were prepared. The composites with co‐continuous phase structure exhibited much better dielectric properties than those with sea–island structure. Then, PEEK/TPI/MWCNTs composites with the same PEEK/TPI ratio but various MWCNTs contents were prepared. The dielectric constant of the composite with 2 wt% MWCNTs reached 11306, which is because the formation of a co‐continuous phase structure benefited the mini‐capacitor network. Our results provide an effective method to develop high‐dielectric‐constant composites using the concept of double percolation. © 2015 Society of Chemical Industry 相似文献
7.
The conducting polymer composite material is desired to have a high dielectric constant and high dissipation factor in low and high frequency ranges, so that it can be used in charge storing devices, decoupling capacitors, and electromagnetic interference (EMI) shielding applications. Currently, on‐going research is trying to enhance the dielectric constant of ceramic powder‐polymer, metal powder‐polymer, and nanotube‐polymer composites in the low frequency region. In this article, we present the dielectric properties of polypropylene (PP)‐graphite (Gr) composites in low and radio frequency ranges. Furthermore, the EMI shielding properties of these composites are examined in the radio frequency range. The PP‐Gr composites were prepared by mixing and the hot compression mold technique. The electrical conductivity and dielectric constant of PP‐Gr composites with graphite volume fraction follow the power law model of percolation theory. The percolation threshold of the composites is estimated to be 0.0257 (～ 5wt % of Gr). The current of PP‐Gr composites as a function of voltage shows a nearly ohmic behavior above the percolation threshold. Shore‐D hardness of the composites is decreased with the addition of conducting filler. The PP‐Gr composites exhibit a high dielectric constant and high dissipation factor with the addition of graphite in low frequency and radio frequency regions, so they can be used in the proposed applications. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
8.
本论文用一种新方法粉碎制各片状石墨微粉（graphite sheet,GS）,同时用此法所得的片状石墨微粉与不饱和树脂（UPR）制成UPR／GS导电复合材料。通过研究其渗滤阀值来研究其复合体系的导电性能,探索该方法的实用价值。 相似文献
9.
Slavica Maletić Nataša Jović Orsini Mirjana Milić Jablan Dojčilović Amelia Montone 《应用聚合物科学杂志》2024,141(5):e54881
Epoxy-rich carbon-based composites are well recognized materials in industries owing to their good mechanical properties and thermal stability. Here, dielectric properties of composites based on bisphenol-A-epoxy resin loaded with 5, 6, 10, and 15 wt% of graphite flakes (GF) have been studied. The frequency and temperature dependence of the dielectric permittivity, dielectric loss, and ac conductivity have been examined in temperature (−103 to 97°C) and frequency (20 Hz–200 kHz) range. Influence of the filler surface chemistry have been studied for composites loaded with 5 wt% GF obtained: (i) under wet milling, without or with adding Triton-100x as a surfactant, or (ii) under dry milling in the presence of KOH. The composite made of epoxy loaded with 5 wt% exfoliated expanded graphite flakes (EEG), was also prepared. The surface treatment with KOH notably increased dielectric constant of the composite, keeping low dielectric loss, while treatment with Triton-100x significantly increased tanδ. The composite loaded with exfoliated expanded graphite shows higher ac conductivity than those obtained with flaky graphite, GF. Possibility to change dielectric properties of the composites without changing the loading content can be used as an approach in tailoring one with desired dielectric properties. 相似文献
10.
Yun‐Chuan Xie De‐Mei Yu Chao Min Xiu‐Sheng Guo Wei‐Tao Wan Jing Zhang Hong‐Lu Liang 《应用聚合物科学杂志》2009,112(6):3613-3619
Composites of an expanded graphite/diglycidyl ether of bisphenol A (DGEBA) were prepared by a simple melt blending method, and their dielectric and mechanical properties were investigated. During observations of fractured surfaces of the composites, the graphite sheets were seen to be homogeneously dispersed in the epoxy matrix. Moreover, the composites presented an enhanced dielectric constant (～ 180) and a low loss factor (～ 0.05) at 50 Hz, suggesting their potential suitability for embedded dielectric applications. The enhanced dielectric constant can be explained by the percolation theory and the relatively low loss factor was attributed to strong interfacial interactions between the polymer molecules and the ? OH/? COOH groups of the expanded graphite, which constrained the orientational polarization of the polarons. Furthermore, dynamic mechanical analysis of the composites showed a restricted macromolecular relaxation and improved mechanical properties. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 相似文献
11.
The thermal conductive composites of polyoxymethylene (POM)/graphite were prepared through four intercalation methods, including melt (MI), solution (SM), pan milling (SMI), and in situ intercalation (IM). For the purpose of improving the interfacial compatibility of POM/graphite, realizing the exfoliation and nano‐dispersion of graphite in POM matrix, the effect of the type and the content of the graphite, the nature of the coupling agents used in graphite modification on the properties of the composites was studied. The results showed that the thermal conductive properties of POM were improved remarkably from the value of 0.36 W/(m K) for neat POM to the value of 1.15 W/(m K) in presence of 30 wt % graphite, and the composites filled with the coupling agent T‐1 or T‐2 surface‐modified colloidal graphite displayed better thermal conductivity. The degree of layers exfoliation of the graphite was enhanced in the order of MI, SM, SMI, and IM. And the composites prepared by SM, SMI, and IM methods presented much more decreased size, more narrow size distribution, thinner overlapped sheets, and better dispersion of the graphite than that prepared by MI method. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 相似文献
12.
The effect of addition of fillers (carbon black (CB), carbon silica dual phase filler (CSDPF), and nanoclays) on the relaxation behavior of chlorobutyl vulcanizates has been studied. The primary relaxation (α‐transition, the glass transition) was studied by dynamic mechanical analysis as a function of temperature (?60 to +100°C) and positron annihilation life time spectroscopy (?70 to +110°C). Irrespective of the filler and its loading, all the composites showed the glass transition temperature in the range of –29 to –33°C, which was explained on the basis of relaxation chain dynamics of polyisobutylene in the vicinity of fillers. The secondary relaxation (α* or β relaxation) was studied using dielectric relaxation spectra in the frequency range of 100–106 Hz. Nanoclays had a profound influence on the secondary relaxation, whereas CSDPF and CB had a marginal effect. The nonlinear strain dependent dynamical parameters were also evaluated at double strain amplitudes of 0.07–5%. The nonlinearity in tan δ and storage modulus has been explained on the concept of filler–polymer interactions and the interaggregate attraction (filler networking). The “percolation limit” of the fillers in the composites has been studied by DC conductivity measurements. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3161–3173, 2006 相似文献
13.
Electrical conductivities of low‐density polyethylene (LDPE)–carbon black (CB) composites were studied using high resistance meter at room temperature (DC conductivity) and dielectric spectroscopy (AC conductivity) in the frequency range between 90 kHz and 13 MHz and temperature range from 120 to 355 K. DC measurements revealed a percolation threshold at about 20 wt % of CB content, whereas AC measurements show two conductivity peaks at about 15% and 23% of CB content. The presence of two percolation thresholds was attributed to different dispersions of CB particles in structural inhomogeneities of LDPE. The experimental data were analyzed using the model of Efros and Shklovskii, which describes the critical behavior of a complex conductivity using critical indexes. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 相似文献
14.
用渗漏理论讨论了SiO_2-C系陶瓷复合材料的组成与宏观电导率的关系,结果表明按渗漏模型所得到的结果与实验结果是一致的。该SiO_2-C系复合陶瓷材料的渗漏阈值Pc(石墨的临界体积百分含量)为0.069,其临界指数t=1.72,即为三维渗漏模型的临界指数值。 相似文献
15.
The dielectric properties and the structure of various metal–polymer composites, based on a polymer matrix of polyamide (PA), polyethylene (PE), polyoxymethylene (POM), or blend PE/POM filled with dispersed iron (Fe) particles, have been investigated in this work. In PE–Fe, PA–Fe, and POM–Fe composites the filler spatial distribution is random. In the PE/POM–Fe composites, the polymer matrix is two‐phase and the filler particles are localized only in the POM phase, resulting in an ordered distribution of the dispersed filler particles within the blend. The concentration and frequency dependence of the dielectric permittivity, ε′, and the dielectric loss tangent, tanδ, are described in terms of the percolation theory. The experimental values of the critical exponents (namely, s, r, and y) are in good agreement with those predicted by the theory for the composites with random filler distribution. The PE/POM–Fe composites demonstrate low value of the percolation threshold, PC, and high values of the critical exponents r and y. This is attributed to the specific structure of these composites. A schematic model for the morphology of the composites studied has been proposed. This model explains the peculiar behavior of the PE/POM–Fe composites by assuming ordered distribution of the filler particles in a binary polymer matrix. The proposed model is in good agreement with the results of optical microscopy. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 3013–3020, 2003 相似文献
16.
N. A. Kamel T. H. Abou‐Aiaad B. A. Iskander S. K. H. Khalil S. H. Mansour S. L. Abd‐El‐Messieh K. N. Abd‐El‐Nour 《应用聚合物科学杂志》2010,116(2):876-885
In this study poly(vinlyl chloride) (PVC) was modified by using ethylenediamine, diethylenetriamine, and ethanolamine as a crosslinker in dimethylformamide. Reaction variables were optimized for getting desired crosslinked PVC, which was further reacted with maleic anhydride to form graft polymer. The anhydride group on further hydrolysis gives carboxylic group, which can exchange proton with other cations.The polymers were characterized by FTIR spectroscopy and thermal analysis (TGA/DTA). Swelling behavior was examined in various electrolytic solutions. Modified PVC have shown good thermal stabilities and absorption capacities in neutral and acidic media, due to which these polymers might find applications in cation exchanger resin and chromatography. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
17.
Prelocalized Acrylonitrile Butadiene Styrene/graphite composites were prepared by hot compression molding technique. The increased conductivity with increase of graphite content exhibits percolation phenomenon. The current–voltage characteristics are found to change from nonlinear to linear above the percolation threshold. A positive temperature coefficient of resistance is observed in these composites, and this effect is more pronounced in samples having graphite concentration near percolation threshold. The dielectric constant was found to increase slowly up to the percolation concentration and beyond it a sudden increase in its value is observed. The dissipation factor exhibits maxima in the vicinity of percolation threshold. The dielectric properties are discussed in terms of the interfacial Maxwell‐Wagner effects. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 相似文献
18.
Wei Ni Jianglin Ye Youmin Guo Chao Cheng Zhongqin Lin Yide Li Hong Wang Yi Yu Qiuju Li Shouguo Huang Zongping Shao Chunchang Wang 《Journal of the American Ceramic Society》2017,100(7):3042-3049
The role of mixed‐valence structure in colossal dielectric constant (CDC) behavior has been investigated in LaFeO3 ceramics by tuning the ratio of Fe2+/Fe3+ through substituting Al for Fe. The ratio of Fe2+/Fe3+ is decreased gradually from 1.0 to 0.0 by increasing the concentration of Al3+. Two clear‐cut correlations have been found: (i) the relationship between the CDC behavior and the ratio of Fe2+/Fe3+ follows an exponential function and (ii) the activation energy of the polaron relaxation is proportional to , where is the intrinsic dielectric constant. These findings underscore the role of the mixed‐valence structure in CDC behavior and suggest that adjusting the mixed‐valence structure through doping/alloying can be a promising strategy to achieve superior CDC behavior in transition‐metal oxides. 相似文献
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20.
To improve dielectric performance of polystyrene (PS) without sacrificing its flexibility and processability, PS encapsulated graphene sheets (PSG) were synthesized by ultrasonically initiated in situ polymerization and was incorporated into PS matrix as fillers. The structure and properties of the obtained PSG were investigated by Fourier transform infrared, transmission electron microscopy, scanning electron microscope, and atom force microscopies. The results showed that the in situ formed PS layers attached on the surface of graphene and there were strong interfacial interactions between them. In virtue of this core‐shell architecture and intrinsic properties of PSG, PS/PSG nanocomposites exhibited improved dielectric performance and a typical percolation transition with very low percolation threshold of 0.2 wt %. Compared with pure PS, significantly increased dielectric permittivity and a low loss tangent were observed for the composites. These composites might be potential flexible dielectric materials for use in high‐frequency capacitors with low loss. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44628. 相似文献