【作者】 张文斌；

【导师】 王勇；

【作者基本信息】 西南交通大学 ， 材料物理与化学， 2015， 硕士

【摘要】 聚合物因其具有优良的加工性能、耐化学腐蚀、成本低廉等特点,在电子封装等领域有广泛的应用。随着电子领域与封装技术的飞速发展,电子产品的体积成千万倍地缩小,而电子产品工作速度越来越过,此时电子设备发热现象愈发明显,使得电子产品的运行效率下降、死机甚至会引发火灾等危害。聚合物导热性能较差,不足以满足工业生产对散热性能的需求,而选用高导热性能填料对聚合物材料进行填充改性已经成为工业常用的提高材料导热性能的手段。因此,研究制备高导热性能高分子材料具有十分重要的意义。本文针对聚偏氟乙烯(Polyvinylidene fluoride, PVDF)基导热复合材料中界面热阻、导热填料网络、极性晶体等对复合材料导热性能的影响规律及其作用机制开展研究工作,旨在掌握改善PVDF复合材料导热性能的方法和技术,阐述其机理,以期为具有高导热系数的PVDF复合材料的开发与应用提供理论支撑和技术指导。主要研究成果如下：(1)首先利用聚乙烯吡咯烷酮(Polyvinyl pyrrolidone, PV P)对碳纳米管(Carbon nanotubes, CNTs)物理包覆制备CNTs@PVP,再通过熔融共混法制备复合材料PVDF/CNTs和PVDF/CNTs@PVP。通过对复合材料导热性能、结晶行为、流变行为、微观形貌的表征,研究PVP对CNTs的分散以及界面热阻的影响。导热系数测试结果表明,当CNTs、PVP含量分别为10wt%、1wt%时,复合材料的导热系数升高至0.63W/mK,达到PVDF导热系数的3倍之多；通过结晶行为研究发现PVP不会引起PVDF晶型的变化；形貌表征及流变行为说明PVP的引入大幅地改善CNTs的分散并构建更致密的导热网络；通过红外分析发现PVP与PVDF间存在氢键作用。综合上述分析表明,CNTs致密的网络结构及PVDF与CNTs间界面相互作用的增强是PVDF/CNTs@PVP复合材料导热性能提高的主要原因。(2)通过溶液共混法将氧化石墨烯(Graphene oxide, GO)引入到复合材料PVDF/CNTs中,制备PVDF/CNTs/GO复合材料。通过形貌表征、流变行为研究发现,GO促进CNTs的分散,并与CNTs形成致密的三维填料网络结构；通过导热性能测试及理论模拟计算发现,GO与CNTs所构建三维导热网络结构是导热性能提高的主要原因。此外,结晶行为研究表明,GO诱导PVDF生成大量极性的y晶体。这意味着GO的引入不但可以降低PVDF/CNTs导热复合材料的生产成本,而且可使PVDF具有更多的潜在应用价值。(3)将离子液体(Ionic liquid, IL)添加到PVDF中,制备共混物PVDF/IL。通过对PVDF结晶行为的研究发现,IL诱导PVDF生成了β极性晶体,并且极性晶体相对含量随IL含量增加而增加；导热测试结果表明,极性晶体的生成有利于PVDF导热性能的提高；初步探索了极性晶体对复合材料导热性能的影响,为进一步改善聚合物导热性能提供了新的研究思路。更多还原

【Abstract】 Due to their excellent corrosion resistance, good processing ability and low manufacturing cost, polymers exhibit a wide range of applications in electronic packaging and other related fields. With the rapid development of microelectronics integration and packaging technology, the volume of electronic components and logic circuits has been shrinking thousands of times, while the operating frequency of the components is increasing rapidly. As a result, the heat generated by electronic equipment is largely accumulated, which makes the devices operate with sharply decreased efficiency, crash and even lead to fires and other hazards. Polymer materials exhibit poor thermal conductivity in general, which make them can’t meet the demand for industrial production. Filling polymer matrix with high conductive fillers has become a common method to improve the thermal conductivity of the materials. Thus, the preparation of highly thermal-conductive polymer materials is of great significance.The present thesis is focused on investigating the influencing mechanism of the interfacial resistance, filler networks, and crystal structure on thermal conductivity of Polyvinylidene fluoride (PVDF)-based polymer composites, aimed to explore new methods and techniques to improve the thermal conductivity of PVDF-based composites and further understand the mechanisms of improvement of thermal performance. It is expected to provide theoretical guidance for the development of thermal conductive polymer materials in industrial production. The main results obtained in the present thesis are listed as follows:(1) In this work, CNTs@PVP was prepared by physically treating carbon nanotubes (CNTs) using polyvinylpyrrolidone (PVP) firstly. Then composites PVDF/CNTs and PVDF/CNTs@PVP were prepared by melt blending method. The effects of PVP on dispersion of CNTs and interfacial thermal resistance between PVDF and CNTs were studied through the thermal conductivity measurement and the characterization of crystallization behavior, rheological behavior and microstructures. The results showed that when the content of CNTs and PVP were 10wt% and lwt%, respectively, the thermal conductivity of the composite was increased to 0.63 W/mK, which is 3 times of that of pure PVDF. The crystallization behavior showed that the addition of PVP will not change the crystal form of PVDF. Morphology characterization and rheological behavior showed that the introduction of PVP greatly improved the dispersion of CNTs and helped CNTs build denser thermal networks. The formation of hydrogen bonding between PVP and PVDF was proved by FTIR. The more integrated CNTs network structure and the intensified interfacial interaction were suggested the main mechanisms for the largely enhanced thermal conductivity of the PVDF/CNTs@PVP nanocomposites.(2) A small amount of graphene oxide (GO) was introduced into poly(vinylidene fluoride) (PVDF)/Carbon nanotube (CNT) composites through solution compounding. The morphology characterization and rheological behavior showed that GO facilitate the dispersion of CNTs, and the CNTs formed a denser three-dimensional network structure. The thermal conductivity and EMT theoretical simulation results showed that three-dimensional network structure constructed by GO and CNTs is the main reason for the improvement of thermal conductivity. In addition, the crystallization behavior demonstrated that GO induced the formation of polar y crystal. Therefore, the introduction of GO can not only reduce production cost of thermal conductive polymer composites, but also broaden the potential applications of PVDF.(3) The ionic liquid (IL) was added to PVDF to prepare the PVDF/IL blends. Results of crystallization behavior characterization showed that IL induced the formation of polar β crystal of PVDF, and the relative crystal content of β form increased with increasing IL content. Thermal conductivity mesurement results showed that polar crystals benefited the thermal performance of PVDF. The effects of polar crystal on thermal conductivity was preliminarily explored. This work provides a new strategy to improve the thermal conductivity of PVDF.更多还原