复合导电高分子材料微观网络结构及导电行为仿真分析

导电填料的形貌、尺寸、材料特性及导电填料之间、导电填料与基体之间的相互作用等因素,均能对复合导电高分子材料的导电行为产生重要的影响。为此,通过建立球状导电填料填充的复合导电高分子材料微观结构模型,利用Matlab计算软件,仿真分析了复合导电高分子材料的导电行为即渗流现象,研究了导电填料的粒径大小和体积分数对复合导电高分子材料导电特性的影响。研究结果表明,该仿真模型能够从整体上反映复合导电高分子材料的导电特性,并能推广到其他形貌的导电填料的情况以及三维领域。     

Novel properties of new type conducting and insulating polymers andtheir composites

Novel properties of recently developed conducting and insulating polymers and their composites are discussed. Properties of conducting polymer whose main chains are composed of unsaturated π-bonds depend strongly on the main chain structure, substituent and also molecular dopants. Various applications of conducting polymers such as electroluminescence (EL) elements, electrolyte capacitors, photoconductors, photovoltaic cells, superconductors and insulators at cryogenic temperature, are discussed by taking effects of molecular dopants such as C₆₀ into consideration. A new type of insulating polymer, syndiotactic polypropylene prepared by newly developed metallocene catalysts has been studied and found to exhibit much superior electrical, thermal and mechanical characteristics compared with those of conventional isotactic polypropylene, atactic polypropylene and polyethylene. These excellent characteristics originate from lower crystallinity, smaller spherulites and different crystal lattice than in isotactic polypropylene. Negligible degradation of syndiotactic polypropylene by contact with copper is interpreted in terms of difference of catalysts and suppression of diffusion of copper cation. New types of conducting polymer, insulating polymer composites were prepared. Their conductivity was controlled over more than 10 orders of magnitude by small amounts of a conducting polymer, polypyrrole, which can be interpreted in terms of the percolation model depending on the shape and density of polypyrrole coated insulating polymer particles. Nonlinear current-voltage characteristics were also studied     

碳纳米管填充的高介电常数聚合物基复合电介质材料

介绍了碳纳米管电性能及其功能化改性、以及利用碳纳米管掺杂聚合物制备柔性高介电常数复合材料的研究现状,发现化学气相沉积法得到的多壁碳纳米管(MWNT)在化学处理前后形成的聚合物基复合材料具有明显不同的分散特性和介电性能.相对于微米级球形导电颗粒填充的复合材料,一维尺度碳纳米管填充的复合材料具有明显低得多的渗流阈值,低渗流阈值可以明显保持聚合物基体优良的机械性能.期望在这一领域从工程电介质的角度做深入的研究工作,以发现碳纳米管在聚合物基复合材料领域所表现出的新特性、新现象.     

Silicone rubber dielectrics modified by inorganic fillers for outdoor high voltage insulation applications

The paper discusses the mechanisms by which inorganic fillers in silicone rubber dielectrics enhance the properties of thermal conductivity, relative permittivity, and electrical conductivity making them useful in outdoor high voltage insulation applications. The addition of alumina trihydrate or silica fillers to silicone elastomers, forming binary composites with enhanced thermal conductivity, is discussed in relation to filler type, particle size, shape, and concentration, and its use as a housing material for non-ceramic insulators to minimize material erosion at dry band arcing sites by lowering hot spot temperature. Also discussed is the enhanced relative permittivity of silicone dielectrics that is obtained through the addition of barium titanate powder which can be further increased with the addition of aluminium powder forming a tertiary composite, resulting in a significant grading of the surface electric field when applied as a housing material to high voltage bushings. Controlled electrical conductivity of silicone dielectrics is discussed through the use of antimony-doped tin oxide filler binary composites and when applied as a housing material to outdoor bushings, the pollution performance is greatly enhanced.     

Influence of filler on the curing and thermal aging of epoxide compounds

An experimental investigation of the filler sort and dispersity influence on inner mechanical stress in UP5–162 epoxide compound during thermal aging was carried out. It was found that the size of filler particles has a dominant influence on a value of the inner mechanical stress, while filler thermophysical properties, such as thermal conductivity and heat capacity, are more important during thermal aging. The backgrounds for maintaining of high mechanical properties of a compound are the filler particle distribution homogeneity over a compound volume, as well as a narrow dispersion distribution.     

Electrical resistance of electroconductive plastic composite with carbon fiber filler

To obtain a new electroconductive composite, the vapor-grown carbon fiber (VGCF) has been applied to the thermoplastic resin composite as a conductive filler. The stability of electrical conductivity of the composite is investigated. The resistivity of VGCF composite is 1.7 × 10^?1 Ω·cm at room temperature which is one order smaller than that of commercial grade composites with carbon filler. The stability of electrical conductivity, under temperature change (?35 to +60°C) and for exposure tests (at room temperature and at 60°C), the VGCF composites have high degree of stability. The stability of electrical conductivity of the present composites are superior to those of conventional carbon fibers such as PAN-based, under tensile stresses and bending stresses. It is suggested that the fine conductive networks in the present composites give rise to these desirable performances.     

高导热绝缘高分子复合材料的研究进展

介绍了高导热绝缘高分子复合材料的导热机理,讨论了影响高导热绝缘高分子材料导热性能的主要因素,阐述了高导热绝缘高分子材料的发展方向。     

Ag/PVA纳米聚合物基复合材料的制备及其电性能研究

通过溶胶-凝胶法制备Ag/PVA纳米聚合物基复合材料，对复合材料的微观结构进行了表征，并对这种复合材料的电学性能进行了研究。结果表明，纳米银可以通过溶胶一凝胶法均匀分散在水溶性的PVA聚合物中，并且这种复合材料具有独特的电学性能，即在合适的纳米银含量时这种复合材料表现出高于其基体的电阻率和击穿场强，并且低温下这种现象更加显著，利用纳米金属粒子在绝缘体中的库仑阻塞效应对这些结果进行了解释。     

Microvaristors: Functional Fillers for Novel Electroceramic Composites

Microvaristors are tiny electroceramic particles, which have highly nonlinear, voltage controlled electrical transport properties and can be used as active fillers in a variety of insulating matrix materials for functional composites. Due to the internal grain boundary structure, each individual microvaristor particle shows an IV-characteristics similar to the one known from bulk ceramics, except for the scaled down switching voltage. By controlling the material formulation, the particle morphology and the sintering conditions the switching characteristics of microvaristors can be tailored for specific applications.In the present paper the basic properties of ZnO microvaristors are described and it is shown how they impart their nonlinearity to the composite. A single microvaristor can withstand surprisingly high current loadings, without major changes in their electrical properties. Combined with the high manufacturing flexibility known from polymer processing, the varistor composites can be used for new solutions in overvoltage protection or control of electrical fields.     

Ion transport studies on Al–Zn ferrite dispersed nano-composite polymer electrolyte

A ferrite dispersed PEO based nano-composite polymer electrolyte has been developed in the present work. Formation of nano-composites, change in the structural and microscopic properties of the system have been investigated by X-ray diffraction, optical microscopy and SEM imaging. Existence of spinodal decomposition structure indicates formation of nano sized composite polymer electrolyte. Increase in formation of crystalline domain has been evidenced in thermal studies upon dispersal of nano-sized filler particles in pristine electrolyte matrix. The ionic transport studies through impedance spectroscopy exhibit highest electrical conductivity for the composition [93PEO-7NH₄SCN]:2 wt% Al–Zn ferrite, viz. is 1.22?×?10^?4 S/cm at room temperature with ionic transference number in excess of 0.9. Arrhenius type thermally activated conduction process is reflected during temperature dependent conductivity studies on these electrolytes.     

Electrorheological properties of anisotropically filled elastomers

We report the results of numerical simulations for the change of both mechanical and electrical properties of elastomers with anisotropically filled polarizable particles under capacitively graded electric and mechanical fields. Such composites have potential applications in electromechanical control. We have used numerical techniques to study the effect of particle shape, permittivity/conductivity ratio, and spatial arrangement on the shear modulus as a function of the electric field. We also investigated the influence of the high field and nonlinear conductivity in the polymer matrix. The results indicate that electrostatic energy and changes therein, which result in electro-rheological effects, are concentrated between particles, and that the electrostatic interaction between the particles is concentrated in a very narrow regime at the tip of the particles, The interaction increases with the electric field intensity until the field between the particles is high enough to cause nonlinear electrical conduction in the polymer, resulting in a redistribution of the electric field and electrostatic energy     

WC/Cu大电流滑动电接触材料的研究

为了提高电接触材料的导电、导热等性能,笔者采用粉末冶金溶渗技术制备出WC/Cu滑动电接触材料,并对其显微组织和性能进行了系统研究。结果表明:WC60～90/Cu滑动电接触材料随着WC含量的增加,材料的密度由11.508 g/cm3增加到13.305 g/cm3,硬度由HB187增加到HB477,导电率由14.6 m/(Ω.mm2)下降到10.6 m/(Ω.mm2)。耐磨性随着WC含量的增加显著提高,但高Cu含量的孕育期较长。磨损机制以磨粒磨损和表面接触疲劳为主。建议使用含量为WC70/Cu30～WC80/Cu20的滑动电接触材料。     

The role of inorganic fillers in silicone rubber for outdoor insulation alumina tri-hydrate or silica

A systematic study to understand how alumina tri-hydrate (ATH) and silica fillers improve the erosion resistance of silicone rubber during dry band arcing showed that the thermal conductivity of the resulting composite material is the main criterion governing material erosion. The thermal conductivity of the composite material is dependent on the thermal conductivity, concentration, particle size, and bonding of the filler particles to the silicone matrix. In this context, either filler can be shown to perform better than the other, depending on the formulation, in the ASTM inclined plane tracking and erosion test. Therefore, the industry perception that ATH filler imports better erosion resistance than silica in silicone rubber can be misleading. The release of water of hydration from ATH appears to have a secondary effect that may be more relevant in silicone compositions having a low concentration of a filler.     

Nanocomposites-a review of electrical treeing and breakdown

Polymer nanocomposites are composite materials having several wt% of inorganic particles of nanometer dimensions homogeneously dispersed into their polymer matrix. This new type of polymer composite has recently drawn considerable attention because nanocomposites or nanostructured polymers have the potential of improving the electrical, mechanical, and thermal properties as compared to the neat polymers [1]. Polymer nanocomposites are, among other applications, increasingly desirable as coatings, structural, and packaging materials in a wide range of automobile, civil, aerospace, and electrical engineering applications. Also, nanocomposites find applications in medical services, healthcare, and decorative coloring [2], [3]. These new materials show excellent mechanical properties such as high tensile strength, increased hardness and toughness, improved flexural strength modulus, and greater heat and chemical resistance. Polymer nanocomposites are characterized by an enormously large interfacial surface area between the inorganic particles and the polymer matrix into which they are embedded. This ratio is typically more than two orders of magnitude greater than that in traditional microcomposite materials. The percentage by weight of the nanoparticles is usually quite low because of the low nanoparticle percolation threshold, particularly for the commonly used platelet and nanotube particles [4]. However, when the nanoparticle content increases beyond the percolation threshold, the nanocomposite may loose its beneficial properties [5]. Various polymers such as polyamide (PA), polyethylene (PE), polypropylene (PP), ethylene vinyl acetate (EVA), epoxy resin (EP), and silicone rubber (SiR) can be combined with inorganic particles such as layered silicate (LS), silica (SiO2), titania (TiO2), alumina (Al2O3), and magnesia (MgO) [1], and there are a number of papers that describe the tests and the properties of the aforementioned combinations of materials [6]?[10].     

石墨颗粒级配对复合板导电及阻气性能的影响

通过模压工艺制备了石墨-酚醛树脂复合板。考察了不同石墨颗粒级配情况下复合板的导电和阻气性能。实验发现粒度比和体积分率对石墨聚合物复合板性能有重要影响。150目石墨和50目石墨配比,复合板导电性能出现先上升后下降的趋势,150目石墨和50目石墨的配比为0.05∶0.95时导电性能最好,而325目石墨和50目石墨配比,复合板导电性能出现单调上升的趋势。150目和325目石墨分别与50目石墨以0.01∶0.99配比时,复合板阻气性能达到最佳。     

Water diffusion into and electrical testing of composite insulator GRP rods

This paper describes water diffusion into and electrical testing of unidirectional glass reinforced polymer (GRP) composite rods used as load bearing components in high voltage composite (non-ceramic) insulators. The tests were performed following ANSI standard C29.11 Section 7.4.2 that can be used to evaluate electrical properties of composites. The unidirectional composite rod materials based on either E-glass or ECR-glass fibers with modified polyester, epoxy and vinyl ester resins were investigated. Two types of ECR-glass fibers were considered, namely high and low seed (voids). The effects of composite surface sandblasting, mechanical pre-loading and nitric acid exposure on the electrical properties of the composites were studied. In addition to the required data of the ANSI standard, the specimen mass gain was also measured after boiling for 100 h. Most importantly, there was no correlation found between the mass gain and the leakage current for different composites. The materials with high seed ECR-glass fibers had much higher leakage currents and they absorbed less moisture than the composites based on either the low seed ECR-glass fibers or E-glass fibers. It was shown in this work that different types of sandblasting, as well as mechanical preloading with and without acid exposure had a negligible effect on the leakage currents and water mass gain of the composite specimens.     

纳米AlN改性对干式变压器环氧树脂绝缘性能的影响

聚合物纳米复合材料因其优良的电气绝缘性能在电介质绝缘领域得到了广泛应用。为了获得性能优良的环氧树脂绝缘材料,将采用硅烷偶联剂进行表面处理后的纳米Al N颗粒加入环氧树脂绝缘材料中,采用溶液共混法制备了Al N质量分数分别为0%、0.5%、1%、3%、5%、7%的Al N/环氧树脂复合材料,研究了不同Al N质量分数对Al N/环氧树脂复合材料绝缘性能的影响。结果表明,树脂基体和Al N填料之间实现了有效的结合,提高了环氧树脂的热稳定性;Al N的加入一定程度上减小了复合材料的体积电阻率,并且增大了复合材料的介质损耗因数,但对复合材料电气绝缘性能的影响较小;当纳米Al N颗粒质量分数为3%时,Al N/环氧树脂复合材料的交流击穿电场强度最大。因此,添加适量纳米Al N颗粒能够提高干式变压器环氧树脂的电气绝缘性能。     

微米氮化硼-纳米氧化铝复合环氧材料的导热与绝缘特性

环氧树脂(epoxy resin,EP)以其粘附力强、绝缘性能好等优点,在电气领域中得到广泛应用.但环氧树脂的低热导率限制其在器件中的使用,尤其在高频条件下.文中通过多巴胺改性微米氮化硼和纳米氧化铝,将制备的微纳米二元填料填充环氧树脂,研究环氧树脂复合材料的导热性能和电气绝缘性能.结果表明,质量分数22.5％BN和7....     

液晶离聚物/PEO固体聚合物电解质的研究

采用溶液铸膜法制备了含磺酸离子液晶离聚物(LCI)-PEO-高氯酸锂全固态聚合物电解质(SPE)。运用扫描电镜、数字显微镜、差示扫描量热法(DSC)、拉伸测试和交流阻抗对复合电解质膜的性能进行了表征,研究了液晶离聚物(LCI)对电解质结晶度、力学性能以及电导率的影响。结果表明,液晶离聚物(LCI)的加入虽然增加了聚合物电解质的结晶度,但是提高了电导率。当液晶离聚物(LCI)含量为3%时,电解质的室温电导率达最大值,为1.30×10-5S/cm。     

Effects of nano- and micro-filler mixture on electrical insulation properties of epoxy based composites

This paper focuses on the electrical insulation properties of a newly prepared composite material by nano- and micro-filler mixture. Nano- and micro-filler mixture composites were made by dispersing nano-scale layered silicate fillers and micro-scale silica fillers in epoxy resin. To investigate the effects of nano- and micro-filler mixture, the thermal expansion coefficient and insulation breakdown properties by a needle-plate electrode method were measured for the filler mixture composite and the conventional filled epoxy. The filler mixture composite had almost the same thermal expansion coefficient as the conventional filled epoxy. In a continuous voltage rising test, the filler mixture composite had 7% higher insulation breakdown strength than the conventional filled epoxy. Moreover, under constant AC voltage (10 kV at 1 kHz), the filler mixture composite had an insulation breakdown time of more than 20,000 minutes whereas the conventional filled epoxy had a breakdown time of 830 minutes. Electron microscope observation showed that the area surrounded by dispersed micro-scale silica fillers were also filled with the nano-scale layered silicate fillers. Furthermore, the estimate of spacing between the fillers and the filler/epoxy interface area showed a more densely-packed structure of the filler mixture composite than the conventional filled epoxy. The morphological feature of the filler mixture composite seems to improve its insulation breakdown strength and time.