【作者】 徐文武；

【导师】 郑强； 宋义虎；

【作者基本信息】 浙江大学 ， 材料学， 2006， 硕士

【摘要】 本文研究了聚丙烯/乙丙橡胶/炭黑(PP/EPDM/CB)复合材料的导电行为,着重考察了电阻率对轴向压力和温度的依赖性关系,同时还考察了填料质量分数、结晶对复合材料导电性能的影响。 通过分析导电复合材料的电阻率—填料质量分数关系,发现PP/EPDM/CB复合材料呈现典型的渗流导电行为。对材料电阻率-炭黑含量关系拟合发现,临界导电指数与经典统计渗流理论的结果偏差较大,而与平均场理论值较为接近。 在单轴压力作用下,PP/EPDM/CB复合材料轴向导电行为呈现显著的压阻行为。CB含量高于渗流阈值时,复合材料仅表现电阻负压力系数(NPCR)效应,而几乎不表现电阻正压力系数(PPCR)效应。随CB含量增加,电阻回复性与循环稳定性得以提高。循环压缩或预压缩可提高电阻回复性和压阻稳定性。此外,与高分子材料的应力松弛和蠕变相似,在应力作用下复合材料电阻呈现时间依赖性。 研究了PP/EPDM/CB导电复合材料在热循环过程中的导电行为,结果表明在升温过程中PTC/NTC强度随CB含量增加而降低。在降温过程中,CB含量对NTC强度无显著影响。复合材料导电性能的变化与晶体熔融、结晶所导致的凝聚态结构变化有关。更多还原

【Abstract】 Conductive behavior for carbon black (CB) filled polypropylene/(ethylene-propylene-diene terpolymer) (PP/EPDM/CB) composites was studied. Resistivity dependence on the uniaxial pressure and ambient temperature were investigated. The effects of the filler volume fraction and crystallization were also discussed.The relationship between resistivity and filler weight fraction for PP/EPDM/CB composites was analyzed. The composites exhibited typical percolation characteristic. The conductive behavior in PP/EPDM/CB composites followed the prediction of mean-field theory.Results revealed that resistance of PP/EPDM/CB conductive composites strongly depends on uniaxial pressure, showing marked piezoresistivity behavior. In general, above the percolation threshold, resistance exhibits a negative pressure coefficient of resistance (NPCR) effect and positive pressure coefficient of resistance (PPCR) effect could hardly be observed. The reversibility and stability of piezoresistance increase with CB concentration. It is found that the piezoresistive stability could considerably be improved through repeated compression with the same level of maximum stress. The resistance of the composites also demonstrates the creep and relaxation behaviors similar to strain and stress do.Furthermore, conductive behavior of PP/EPDM/CB composites undergoing thermal cycles was investigated. It can be found that with increasing CB content, the intensity of both negative temperature coefficient (NTC) and positive temperature coefficient (PTC) effects decrease during the heating processes. However, degree of resistance change is almost independent of CB content during the cooling processes. Besides, the melt and crystallization of the composites were preliminarily studied in the thesis. It is found that there exist some notable affect of melt and crystallization on the conductive behavior.更多还原