弹性相变复合材料的导热网络设计及机理研究

In order to meet requirement of heat dissipation of a kind of component, it is necessary to prepare a new type of thermally conductive interface materials with high thermal conductivity, good elastic property, large phase change enthalpy and low leakage rate, and to design its thermally conductive network, then to study its thermally conductive mechanism. The project will emulsify phase change materials and supporting materials to form latex with some charges on its surface, and then will add dispersion of thermally conductive fillers with reverse charges into the latex for emulsion blending. A kind of core-shell structure of latex particles @ thermal fillers will be formed by self-assembly between positive charges and negative charges. Finally, thermally conductive and elastic phase change composites with segregated structure will be prepared by hot-compression and vulcanization. The thermally conductive fillers will be gathered at interface of cells in segregated structure to form thermally conductive network, and micro-structure of the thermally conductive network will be related to shape, size and size distribution of cells in segregated structure. Therefore, thermally conductive network of elastic phase change composites can be designed, and thermally conductive mechanism of elastic phase change composites can be studied. Then numerical calculation model can be established to predict and design properties of thermally conductive and elastic phase change composites. The results of the project can provide experimental basis and theoretical guidance for preparation and performance design of thermally conductive and elastic phase change composites, which are of theoretical and practical value for study on thermally conductive interface materials.

为满足某部组件散热要求，需要研制热导率高、弹性好、相变焓大且渗漏率低的界面导热材料，并设计弹性相变复合材料的导热网络，研究其机理。项目选择结构相近的相变材料和弹性支撑材料，通过乳化研究形成胶乳，且乳胶粒表面带一定的电荷；然后将带相反电荷的改性导热填料分散液加入胶乳中乳液共混，在静电相互作用下自组装形成乳胶粒@导热填料核壳结构，再通过热压硫化成型制备具有隔离结构的导热弹性相变复合材料。导热填料聚集在隔离结构单胞界面处形成导热网络，导热网络的微观结构与隔离结构单胞的形状、尺寸及尺寸分布有直接关系，因此通过制备工艺可以调控隔离结构单胞，设计弹性相变复合材料的导热网络，进而研究其导热机理，得到性能的影响因素及规律，并建立数值计算模型，实现弹性相变复合材料性能的可预测和可设计性。项目研究结果，能为导热弹性相变复合材料的制备和性能设计提供实验依据和理论指导，对界面导热材料的研究具有理论意义和应用价值。

项目针对相变材料易渗漏、导热率小、稳定性和力学性能较差等问题，选取具有优异力学性能和良好防渗性能的三元乙丙橡胶（EPDM）作为高分子支撑材料，将石蜡和EPDM一起通过乳化法制备得到相变胶乳（PCL），研究了乳化剂种类、乳化剂含量、乳化速率和石蜡含量对PCL性能的影响。将PCL通过热压硫化成型得到了石蜡/EPDM定形相变材料，探索了石蜡/EPDM的定形机理。通过Pickering乳化法，利用氧化石墨烯（GO）的两亲性，将GO以助乳化剂的形式引入PCL中，使GO包覆在PCL乳胶粒表面，再通过化学还原形成石蜡@EPDM@rGO双壳层核壳结构，热压硫化得到弹性定形相变材料（ESPCMs），研究了不同rGO含量对ESPCMs性能的影响。通过胶乳共混将正电改性的石墨烯（GE）引入带相反电荷的石蜡/EPDM相变胶乳中，使PCL和GE因静电相互作用自组装形成石蜡@EPDM@GE双壳层核壳结构，再通过硫化得到导热弹性定形相变材料（TSPCMs），研究了GE含量对TSPCMs热导率的影响。此外，项目以石蜡为相变材料，GO和碳纳米管（CNTs）自组装得到的三维结构气凝胶作为骨架，探究了不同GO/CNTs配比制备的气凝胶（GCA）对石蜡/rGO-CNTs导热定形相变材料（PGCA）性能的影响，探索了石墨烯和碳纳米管之间的协同导热机理。通过对导热定形相变材料的热导率、相变焓、渗漏率、制备工艺的系统优化设计，掌握了导热弹性定形相变材料的制备和性能表征技术，研究了导热填料的选择与配比对定形相变材料导热性能的影响，分析了导热弹性定形相变材料的相变过程和传热行为，建立了定形相变复合材料的导热模型，探索了传热机理。项目研究结果为导热弹性定形相变材料的设计和制备提供了理论指导和实验依据，具有重要的意义和价值。