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首页> 外文学位 >Enhanced percolative properties from controlled filler dispersion in conducting polymer composites (CPCs).
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Enhanced percolative properties from controlled filler dispersion in conducting polymer composites (CPCs).

机译：通过在导电聚合物复合材料（CPC）中控制填料的分散，增强了渗透性。

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摘要

Conducting polymer composites (CPCs) have been studied since the 1950's and till date remain the focus of theoretical and experimental studies. With CPCs, the need often arises to preserve particular inherent properties of matrix and/or filler phase, such as mechanical, thermal or electrical properties in the final composite. Unfortunately, commonly used dispersion techniques fall short of assuring these goals because they alter the original polymer structure and require high filler loadings thereby compromising cohesive strengths, as is commonly observed with melt and solution mixing techniques. Even when component properties can be preserved and filler requirements are low, as in dry mixed systems, mechanical properties still remain poor. Therefore, a major challenge in processing CPCs is the need to balance high electrical conductivity with an acceptable mechanical performance, which sets the tone for this study. In this work, three commonly used blending techniques (dry, wet and complete solution methods) were optimized and the property results compared against a novel partial solubility mixing model based on the standard solubility parameter concept. The experimental design required a controlled swelling of the polymer particles, avoiding actual dissolution, such that filler particles of much smaller particle size can be embedded within the swelled polymer structure. The swelling parameter, developed as a function of mixing time, polymer particle size and solubility parameter, served as a useful tool for process control and property development. Powder compositions of poly(acrylonitrile butadiene styrene) and poly(styrene butadiene styrene) block copolymers were first classified into narrow size ranges. Using developed solvent solubility parameters (linked to swelling ratios), a controlled coating of conductive (graphite, polyaniline) and non-conductive fillers (alumina) was deployed over the polymer particles. These were dried and compression molded at 120--130°C and 110 MPa pressure for 5 minutes. Characterization was done by SEM (after fine polishing), compression testing and XRD analysis. A significantly low percolation concentration of 0.047 vol. % was obtained for a dry mixed composite when the mean polymer matrix/filler particle size ratio was ∼90. As a result of the narrow particle size classification of blend components and the application of a novel dispersion technique, percent standard deviation was reduced to single digits. In the absence of particle size classification, the standard deviation was higher by a factor of 3 and 7. A percolation concentration of 0.23 vol. % was achieved for partial solution mixing, which value is a decade lower than that for solution mixing. Compressive yield strength, used as a measure of composite cohesion, was much improved under partial solution mixing, and at ∼32 MPa, it was about 25--60% higher than for other three mixing methods tested. The use of inert filler and the development of solubility parameter as processing aid in partial solution mixing were also effective tools in the reproducible control of electrical percolation and resulted in composites with high temperature coefficient of resistivity (TCR) of up to 5000 ppm/°C. High piezoresistive coefficients of up to -2.5 MPa-1 were also obtained for 5 wt. % graphite filled composites.
机译：自1950年代以来，一直对导电聚合物复合材料（CPC）进行过研究，直到现在仍是理论和实验研究的重点。对于CPC，经常需要保持基质和/或填料相的特定固有性质，例如最终复合材料中的机械，热或电性质。不幸的是，常用的分散技术不能确保这些目标，因为它们改变了原始的聚合物结构并需要高的填充量，从而损害了内聚强度，这在熔融和溶液混合技术中通常会看到。即使在保留成分特性且填料要求低的情况下（如在干混系统中），机械性能仍然仍然很差。因此，处理CPC的主要挑战是需要在高电导率与可接受的机械性能之间取得平衡，这为这项研究奠定了基调。在这项工作中，对三种常用的混合技术（干法，湿法和完全溶液法）进行了优化，并将性能结果与基于标准溶解度参数概念的新型部分溶解度混合模型进行了比较。实验设计需要控制聚合物颗粒的溶胀，避免实际溶解，从而可以将较小粒径的填料颗粒嵌入溶胀的聚合物结构中。作为混合时间，聚合物粒度和溶解度参数的函数而产生的溶胀参数，是用于过程控制和性能开发的有用工具。首先将聚（丙烯腈-丁二烯-苯乙烯）和聚（苯乙烯-丁二烯-苯乙烯）嵌段共聚物的粉末组合物分为窄尺寸范围。使用开发的溶剂溶解度参数（与溶胀率相关），将导电（石墨，聚苯胺）和非导电填料（氧化铝）的受控涂层铺在聚合物颗粒上。将它们干燥并在120--130°C和110 MPa的压力下模压5分钟。通过SEM（精细抛光后），压缩测试和XRD分析进行表征。 0.047 vol。的低渗滤浓度。当聚合物基质/填料的平均粒径比为〜90时，干燥混合复合材料的百分含量为％。由于混合组分的粒度分类狭窄，并且采用了新颖的分散技术，因此标准偏差百分比降低到个位数。在没有粒度分类的情况下，标准偏差分别为3和7倍。渗滤浓度为0.23 vol。对于部分溶液混合，达到了％，该值比溶液混合的值低十倍。在部分溶液混合下，用作复合内聚力的量度的抗压屈服强度得到了很大的改善，在〜32 MPa时，它比测试的其他三种混合方法高约25--60％。惰性填料的使用和溶解度参数的发展作为在部分溶液混合中的加工助剂也是可重现控制电渗流的有效工具，并导致复合材料的高温电阻率（TCR）高达5000 ppm /°C 。对于5wt。％，也获得高达-2.5MPa-1的高压阻系数。 ％石墨填充的复合材料。

著录项

  • 作者

    Balogun, Yunusa A.;

  • 作者单位

    University of Cincinnati.;

  • 授予单位 University of Cincinnati.;
  • 学科 Engineering Mechanical.;Engineering Materials Science.;Engineering Metallurgy.
  • 学位 Ph.D.
  • 年度 2009
  • 页码 278 p.
  • 总页数 278
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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