HDPE/CB高分子导电复合体系的单轴形变与压阻行为

根据基体形变及其与渗流网络结构之间的关系,研究了高密度聚乙烯(HDPE)/炭黑(CB)复合材料压阻行为的发生机制及其影响稳定性的力学因素.结果表明,单轴压阻行为的产生源于材料受外力变形而导致的渗流网络微结构变化,且这种变化强烈依赖于填料含量.当填料含量较低时(渗流阈值附近),体系电阻率随压力升高而表现为电阻正压力系数行为;当填料含量较高时,体系电阻率随压力升高显现电阻负压力系数效应.完全卸载的零压力下,电阻基线随压缩循环随循环次数增大而发生漂移,这种漂移与轴向残余压缩应变有关,可以通过增加循环次数来加以稳定.交联可以减小残余压缩应变,并抑制高填充复合体系电阻基线的漂移.

RELATIONSHIP BETWEEN UNIAXIAL DEFORMATION AND PIEZORESISTANCE FOR HDPE/CB COMPOSITES

The mechanism of piezoresistive behavior and the improvement of its stability for high-density polyethylene/carbon black(HDPE/CB) composites were studied.The results revealed that the uniaxial piezoresistive behavior resulted from the change in the structure of the percolation network,depending on the filler volume fraction φ and the deformation of the material under pressure.When φ approached the percolation threshold φ_c,with increasing external pressure the composites exhibited a positive pressure coefficient(PPC) effect for its resistance.In the case of φ far beyond the φ_c,only a negative pressure coefficient(NPC) effect for its resistance can be observed.The resistance baseline at zero pressure after unloading shifted upward or downward with the increase of the numbers of compressive cycles,depending on the φ.The shift of the baseline was related with the residual compressive strain and can be stabilized by increasing the number of the compressive cycles.Crosslinking of the matrix can restrict the residual compressive strain and stabilize the baseline shift of the resistance-time curve,especially for the composites with a high φ.