【作者】 曹清华；

【导师】 沈烈；

【作者基本信息】 浙江大学 ， 高分子材料， 2012， 硕士

【摘要】 聚合物基导电复合材料的导电性能取决于复合体系的导电网络,而导电填料本身的种类、微结构以及分散状况等因素对导电网络具有至关重要的影响。炭黑(CB)微结构多样、品种齐全,与聚合物复合易成型加工,所得制品导电性能持久稳定,是目前应用最为广泛的导电填料。因此,本文研究炭黑微结构对复合材料导电性能的影响,并探索导电复合材料在电阻焊接领域中的应用。首先,本文采用三种平均粒径相近而微结构不同的炭黑填充到聚丙烯(PP)基体中制备成导电复合材料,考察这三种不同复合体系的导电渗流和流变渗流。结果表明,低比表面积炭黑CB-N660、中比表面积炭黑CB-K300及高比表面积炭黑CB-K600填充聚丙烯复合体系出现导电渗流和流变渗流现象所需的炭黑含量依次减少。这是由于炭黑平均粒径接近时,比表面积越大,相同含量的炭黑在聚丙烯基体中的颗粒密度越大,越易形成炭黑网络结构。而导电渗流是炭黑网络在电场中的电学响应,流变渗流是炭黑网络在应力场中的力学响应,因此两者的渗流闽值相近。其次,本文考察了三种不同微结构炭黑填充聚丙烯复合材料的体积电阻率-温度效应,发现高比表面积炭黑CB-K600填充聚丙烯复合体系具有特殊的NTC-PTC-NTC三阶段体积电阻率-温度效应。另外,高比表面积炭黑CB-K600填充聚丙烯复合体系的PTC效应弱,电发热温度可以高于聚丙烯基体熔融温度,因此可用于热塑性聚合物及其复合材料的电阻焊接领域。最后,将高比表面积炭黑CB-K600填充聚丙烯复合材料制备成加热单元,采取简单搭接焊接形式,电阻焊接连续玻璃纤维增强聚丙烯(CGF-PP)复合材料样条,详细探讨了加热单元的性质、焊接电压、焊接时间和焊接压力等工艺参数对焊接质量的影响,CGF-PP样条的焊接系数在0.55～0.70之间。更多还原

【Abstract】 The conductive property of polymer-based composites depends on the conductivity network. The type, microstructure, dispersion of conductive filler and other factors have an important effect on the conductivity network. Carbon black (CB) is most widely used, because it not only has varieties types and microstructure, but also easily compounded with polymer, and the conductivity of products is lasting stability. In this thesis, the effect of carbon black microstructure on the property of conductive composites was investigated, and the conductive composites in the field of resistance welding application were explored.Firstly, three kinds of carbon black with different microstructure which had similar average particle size filling polypropylene (PP) matrix were prepared. The conductive percolation and rehological percolation of the three composite systems were investigated. Results showed that low surface area carbon black CB-N660, the middle surface area carbon black CB-K300and high surface area carbon black CB-K600filled polypropylene composites all appeared conductive percolation phenomena and rheological percolation, but the required carbon black content was reduced with the surface area increasing. This was due to the particle density of carbon black in the polypropylene matrix, and the greater surface area of carbon black, the easier to form carbon black network. The carbon black network exhibited conductive percolation in response to the electric field and rheological percolation in response to the mechanical stess field, so the percolation thresholds were close.Secondly, volume resistivity-temperature characteristic of the three composite systems was investigated. Results showed that composites filled with high surface area carbon black CB-K600had a special resistivity-temperature characteristic,"NTC-PTC-NTC" characteristic. In addition, the PTC effect of CB-K600/PP composite was weak, and the electrical heating temperature could be higher than the melting temperature of PP matrix, so it could be applied in resistance welding field to join thermoplastic polymers and its composites. Finally, heating element made of polyproylene filled with high surface area carbon black CB-K600was prepared. Taken the form of a simple overlap welding, continuous glass fiber reinforced polypropylene (CGF-PP) composite specimens were resistance welded, and the properties of heating element, welding voltage, welding time, welding pressure and other process parameters on the welding quality were discussed in detail. The welding coefficient of CGF-PP specimens were between0.55-0.70.更多还原