炭黑-碳纤维填充双组分聚合物体系的导电网络及其阻温特性

以2种不同形态尺寸的导电填料炭黑(CB)、 碳纤维(CF)填充双组分聚合物体系高密度聚乙烯(HDPE)聚丙烯(PP), 制备了四元导电复合材料。研究了导电网络的结构形态及其对材料阻温特性的影响。光学显微镜及SEM 观察表明: 炭黑选择性地分布于HDPE中, 体系中HDPE与PP呈双连续相分布, 形成双渗流导电网络结构。而具有较高长径比的碳纤维在两相基体中均匀分布并贯通多个相区, HDPE导电相区的碳纤维相互桥接形成导电网络。电性能测试结果表明: 体系的体积电阻率与CB/HDPEPP及CBCF/HDPE三元复合体系相比下降了1~5个数量级。同时, 双渗流导电网络的存在也有效抑制了负温度系数(NTC)效应, 提高了循环稳定性。与CBCF/HDPE体系相比, CBCF/HDPEPP体系的NTC效应从2个数量级下降到0.6个数量级, 电阻特征弛豫时间从951s增加到了2370s。 

Conductive network formation and resistivity temperature dependence of binary polymer filled with carbon black and carbon fiber

Quaternary composites consisting of two different types of filler (carbon black and carbon fiber) and binary polymer (polyethylene and polypropylene) were prepared by melt blending. The microstructure of the conductive networks and conductivity properties of the composite were investigated. The results show that the double---percolated networks, as well as the mutual bridging between carbon fiber and conductive high density polyethylene (HDPE) phase region reduce the percolation threshold and improve the conductivity. The volume resistivity of quaternary composites decreases by 1～5 orders of magnitude at the same filler content compared to CB/HDPEPP and CBCF/HDPE ternary system. Meanwhile, the negative temperature coefficient effect is inhibited and the stability of the electrical properties is raised, due to the existence of the double---percolated networks. Compared with CBCF/HDPE ternary system, the NTC effect of CBCF/HDPEPP system decreases from 2 orders of magnitude to 0.6 orders of magnitude, while the characteristic relaxation time increases to 2370s from 951s.