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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/HDPE-PP及CB-CF/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CB-CF/HDPE体系相比,CB-CF/HDPE-PP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951 s增加到了2370 s。
Four-component conductive composites were prepared by filling two-component polymer system of high density polyethylene (HDPE) -polypropylene (PP) with two kinds of conductive filler carbon black (CB) and carbon fiber (CF) The structure of the conductive network and its influence on the temperature resistance of the material were studied. Optical microscopy and SEM observations showed that carbon black was selectively distributed in HDPE. HDPE and PP were distributed in two continuous phases and formed a dual-permeability conductive network. Carbon fibers with higher aspect ratios are evenly distributed in the two-phase matrix and penetrate multiple phase regions. Carbon fibers in the HDPE conductive phase regions are bridged to form a conductive network. The results of electrical property test show that the volume resistivity of the system is 1 to 5 orders of magnitude lower than that of CB / HDPE-PP and CB-CF / HDPE ternary composite system. At the same time, the existence of double percolation conductive network also effectively restrain the negative temperature coefficient (NTC) effect and improve the cycle stability. Compared with CB-CF / HDPE system, the NTC effect of CB-CF / HDPE-PP system decreased from 2 orders of magnitude to 0.6 orders of magnitude, and the resistance characteristic relaxation time increased from 951 to 2370 seconds.