微聚合物构件的高导热机理及其注塑成型关键技术研究

With constantly increased integration level as well as power consumption, efficient cooling has become a key issue in the field of polymer MEMS. However, the existing thermal-conductive polymer materials have bottleneck problems such as low thermal conductivity, high filler composition as well as difficulty in fulfilling micro-scale structures, which constraints their further development. In order to increase the contribution of intrinsic thermal-conductivity of the polymer molecular crystallization/orientation to the largest extent, this project presents a new approach to achieve highly thermal-conductive micro polymer components using microinjection molding technology on the basis of the intrinsic/filling synergistic effect of the composites with multi-field coupling. With the high density polyethylene/ boron nitride (multiwall carbon nanotube) polymer composites as materials, the dynamic rheological characteristics and real-time rheological properties at micro-scale of the composite melt, and the rheology-induced migration of the fillers will be investigated. Then, the crystallization and orientation of the matrix and the morphology evolution rule of the fillers within the micro polymer components obtained with different experimental conditions will be analyzed. Moreover, the formation process of the effective paths for thermal conductivity within both polymer matrix and fillers with the coupled fields of high shear/elongation and rapid-cooling temperature in microinjection molding will be explored, followed by revealing the formation mechanism of the intrinsic/filling synergistic effect for high thermal conductivity. Finally, the key factors affecting the thermal conductivity of the micro components will be investigated in order to obtain the optimal processing parameters and material composition for producing highly thermal-conductive micro polymer components. The investigation results from the present research project will provide theoretical basis and key technology for the applications of the highly thermal-conductive micro polymer components.

随着集成度与功率的不断提高，“散热难”已成为聚合物MEMS领域亟需解决的问题。而目前聚合物导热材料存在热导率低、填料含量高及难于实现结构微型化等制约其发展的瓶颈性难题。为最大限度提高聚合物分子结晶/取向的本征导热贡献率，本项目提出基于多场耦合下复合材料本征/填充协同效应思想，利用微注塑成型方法获取高导热微聚合物构件的新方法。研究高密度聚乙烯/氮化硼（多壁碳纳米管）复合材料熔体的动态流变特性、微尺度在线流变性能及填料的流变迁移规律；分析不同实验条件下微聚合物构件中基体的结晶/取向及填料的形态演变规律；探究微注塑成型高剪切/拉伸场、急冷温度场耦合下有效导热通路分别在复合材料基体与分散相中的形成过程，揭示本征/填充协同高导热性的形成机理；研究微注塑过程中影响微构件导热性能的关键因素，确立高导热微聚合物构件的最佳工艺参数与材料配方。本项目研究结果将为高导热微聚合物器件的应用提供理论基础与关键技术。

为满足换热工程、航空航天、电子通讯、生物医疗以及军事装备等领域的应用要求，聚合物导热材料已成为国内外的研究热点。近年来，随着集成度与功率的不断提高，“散热难”已成为亟需解决的问题。然而，目前聚合物导热材料存在热导率低、填料含量高及难于实现结构微型化等制约其发展的瓶颈性难题。为最大限度地提高聚合物分子结晶/取向的本征导热贡献率，本项目提出了基于多场耦合下复合材料本征/填充协同效应思想，利用微注塑成型方法获取高导热微聚合物构件的新方法。具体研究了高密度聚乙烯/多壁碳纳米管（HDPE/MWCNTs）等复合材料熔体的动态流变特性以及填料的流变迁移规律；分析了不同实验条件下微聚合物构件中基体的结晶/取向及填料的形态演变规律；探究了微注塑成型高剪切/拉伸场、急冷温度场耦合下有效导热通路分别在复合材料基体与分散相中的形成过程，揭示了本征/填充协同高导热性的形成机理；研究了微注塑过程中影响微构件导热性能的关键因素，并确立了高导热微聚合物构件的最佳工艺参数与材料配方。本项目研究证实了从成型加工控制角度出发制备高导热聚合物复合材料的可行性，实现了环保、低成本和微型化的产品制备过程，项目研究成果将为高导热微聚合物器件的应用提供理论基础与关键技术。三年来，基于本项目研究成果已在国内外公开发表学术论文8篇，其中SCI检索论文5篇，EI检索论文3篇；获得优秀会议论文奖1项；授权国家发明专利3项，实用新型专利4项；培养硕士研究生2名；项目负责人由讲师晋升为副教授，并获聘本校硕士生指导教师。