聚乙烯/炭黑复合材料导电体系的结构形态

将导电填料（例如炭黑）加入绝缘的聚合物基体即得到导电复合材料，两组混全物的电阻率随导电填料体积分数的变化而改变，电阻率与导电填料体积分数的关系称为渗流曲线，可分为三个主要区域：低导电填料含量区域，复合材料的电阻率很大，聚合物的电阻率占主导；渗流区域，导电填料含量少量的增加会引起复合材料电阻率很大的提高；高导电填料区域，复合材料电阻率很大的提高；高导电填料区域，复合材料电阻率主要由导电填料的电阻率决定，对于导电复合材料已有大量的实验和理论工作来解释导电复合材料已有大量的实验和理论工作来解释导电填料含量和复合材料各组分的形貌对电性能的影响，其中有效介质普适方程（GEM方程）已经对大量的渗流曲线进行了精确的拟合。聚乙烯／炭黑复合材料中由于炭黑的大量分布很难观测其微观形貌，本文对不同辐照交联程度和不同环境温度下聚乙烯／炭黑复合材料的渗流曲线进行分析，试图找出GEM方程各参数与复合材料各组分形貌的关系，为导电复合材料的设计和制备提供理论基础。

THE MORPHOLOGY OF PE/CB CONDUCTIVE COMPOSITES

The resistivity of the conductive composite varies as a function of the volume fraction of the conductive material.Considerable experimental and theoretical work has been done to examine how the volume fractions and the morphology of the components affect the electrical behavior of the composite materials.The generalized effective medium(GEM) equation gives the complete information on how the volume fraction of components may affect the medium conductivity by taking into an account the intrinsic conductivities and geometries of both components and also their arrangement and orientation in the applied electric fields.In this paper the electrical percolation phenomenon in CB/HDPE composite influenced by crosslinking under different irradiation doses and different ambient temperatures has been investigated.The experimental data regarding the dependence of conductivity on the volume fraction of CB were fitted into the GEM equation.The parameters in the GEM equation,corresponding to the dispersion characters of CB in HDPE matrix,were determined through the computer fitting.The CB particles aggregated constructing a three-dimensional conducting network along the electrical current direction.The polymer matrix,however,is statistically vertical to electrical current direction, hindering conductive particles from contacting each other.The higher the irradiation dose or the ambient temperature,the more serious the hindrance.The electrical conductivity of HDPE composites filled with high-structure CB particles is dominated by percolation mechanism based on a particle-touching model,while crosslinking or ambient temperature increasing causes a larger gap between the conductive particles and makes the conductivity more affectd by tunneling mechanism.