摘要
导电高分子复合材料(CPCs)的研究和开发是当今高分子材料功能化的一个重要课题。CPCs是指在高分子基体中加入一种或多种导电填料制备的具有导电功能的高分子复合材料。CPCs已被大量用于抗静电材料、自发热材料、电磁屏蔽材料、各种传感器材料、气体、石油化工、环境等领域探测材料等。近年来,CPCs在外场刺激下的电性能敏感特性引起了人们的广泛关注,尤其是在拉伸、压缩、有机溶剂刺激下的响应行为的研究更是引人注目。尽管如此,具有不同维数的导电填料对CPCs电性能尤其是外场响应性能的影响尚未完全明确,而这对CPCs的应用至关重要。在本论文中,首先,我们采用熔融共混法制备了具有不同维数填料(炭黑(CB),0维、碳纳米管(CNTs),1维)填充的聚丙烯(PP) CPCs,研究了两种CPCs的逾渗行为。并用填料含量稍高于逾渗值的试样测试了CPCs在拉应力场,拉伸循环拉伸下电性能的演变,并对两种CPCs的电性能演变进行了对比。分析了CPCs电性能在上述外场中的变化机制,并运用该导电机制对本实验的现象进行了解释。根据上述讨论,绘制了循环拉伸情况下两种CPCs的导电网络演变的示意图,对两种CPCs在外力作用下试样内部的微观结构演变进行了直观的描述和对比。
其次,我们采用在真空环境下模压成型的方式制备了CB/PP,CNTs/PP CPCs,显著降低了它们逾渗值。另外,我们观察了真空环境下模压制备的两种CPCs试样在拉应力场和循环拉伸场(应变(ε)≤3%)刺激下电性能的演化,并对比了该CPCs与普通CB/PP,CNTs/PP在外场刺激下电性能的变化及其演变机制的异同。
再次,我们本着制备电性能稳定的CPCs的目的,在不同温度(80℃,120℃)下对试样进行了3个小时的热处理,并比较了热处理前后试样阻值的变化。同时也观察了试样热处理后在拉应力场,循环拉伸力场(ε≤3%)刺激下电性能的演化,并对比了两种CPCs试样在外场刺激下电性能的变化。
我们还对普通试样的液体敏感行为进行了对比研究,探讨了了两种CPCs在良溶剂二甲苯溶剂中的响应率高低及其在浸润-挥发循环过程(IDRs)中液敏行为的稳定性。为了研究材料的液体敏感长期使用性能,观察了两种CPCs在二甲苯溶剂中经过72小时(h)浸润并充分挥发后10个IDRs中的液体敏感行为,并进行了对比分析。观察了在环己烷和四氯化碳刺激下的液体敏感行为,并进行了对比研究。
The investigation and exploitation of conductive polymer composites (CPCs) is one of the hot issues for the functionalization of polymers for a long time. CPCs are prepared by filling one or several kinds of conductive fillers into the one or several polymers. CPCs have been widely used for as antistatic materials, self-regulated heaters, electromagnetic shielding, sensors and detection systems, etc. In recent years, CPCs have received great attention due to their popular applications in many fields, especially for the sensitive stimuli-response behaviors under extension, compression and organic solvent, Based on the description above, basic investigation of CPCs has been studied. Although, the effect of own different dimensions conductive fillers on electrical property of CPCs has not been cleared fully, which is crucial for the applications of CPCs. In this paper, we prepared the CPCs by filling CB (0dimension) or CNTs (1dimension) into polypropylene by melt mixing method, the behaviour of percolation thresholds of both CPCs have been stutied. In the present work, the concentrations of CB and CNTs are7.16vol.%and3.41vol.%, respectively, which are little beyond the percolation thresholds of CNT/PP and CB/PP composites (ca.7.05vol.%and3.24vol.%, respectively). The variation of the electrical resistance of both CPCs under tensile field, stress-strain cycles with strain (ε<3%) and the comparison of the mechanical property and electrical property of both CPCs have been investigated. Then the mechanisms of electric conduction have been summarized. And the phenomena, which are observed, have been explained by mechanisms. Finally, a schematic illustration was drawn to illustrate the mechanism of the different sensing behaviour, micro-structure envolution of the inner of samples has been described directly and compared to the both CPCs under extra field.
Following, we prepared CB/PP, CNTs/PP CPCs by compression in the vacuum environment, and decreased percolation thresholds remarkablely. In addition, the envolution of the electrical property of both CPCs, which have been prepared in two different conditions, under tensile field, cycle tension with strain (ε<3%) has been investigated. The electrical property of both CPCs with different preparation ways has been compared also.
Then, in order to prepare stable CPCs, the samples have been annealed at the different temperatures (80℃,120℃) for three hours. The electrical resistance of annealed samples with samples of before annealed were compared. The variation of the electrical resistance of both CPCs, under tensile field, cycle tension with strain (ε≤3%) has been investigated. The electrical property of both CPCs with different preparation ways has been compared as well.
Finally, the xylene stimuli-response behaviors of both CPCs have been investigated. It's found that the responsivity of CB/PP is higher and the reproducibility of CNTs/PP is higher under10IDRs immersion-drying runs (5min immersion, then15min drying). Moreover, after some samples were immersed in xylene for72h, then absolute drying, the effect of immersion on the responsivity and reproducibility under10IDRs immersion-drying runs have been studied. In addition, the organic liquid (cyclohexane and carbon tetrachloride (CCl4), stimuli-response behaviors of both CPCs have been observed.
引文
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