Effect of flake graphite orientation on thermal conductivity of flake graphite/polypropylene, flake graphite/nylon66 composites
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摘要: 为了研究鳞片石墨在基体中的取向对复合材料导热性能特别是不同方向导热性能的影响，通过双螺杆挤出混合及注射成型制备了鳞片石墨/聚丙烯（PP）、鳞片石墨/尼龙66（PA66）导热复合材料，并利用扫描电子显微镜和超声波测试对制备的样品进行了分析。结果表明：鳞片石墨的粒径越小，平面取向度越高，平面与垂直方向的热导率差值越大。加工中双螺杆挤出机的过度剪切会破坏鳞片石墨的片层结构，影响鳞片石墨导热网络的形成，降低复合材料的热导率，但提高了材料导热的各向均匀性。适度的剪切可以打开鳞片石墨的片层结构，提高复合材料的热导率，注射成型更多影响到制品导热的各向异性。Abstract: The flake graphite/polypropylene (PP) and flake graphite/nylon66 (PA66) thermal conductive composites were prepared by twin screw extrusion and injection molding to study the effect of the flake graphite orientation on the thermal conductivity especially thermal conductivity in different directions of flake graphite/PP and flake graphite/PA66 composites. The results were analyzed by SEM and ultrasonic test. The results show that the smaller particle size is, the higher planar orientation degree is, which makes the difference between the planar and vertical thermal conductivity of the composites bigger. The excessive shear of twin screw extruder can destroy lamella structure of flake graphite, influence the formation of the heat conducting network and reduce the thermal conductivity, but improve the uniformity of heat conducting in different directions of the composites. The moderate shear can open the lamellar structure of flake graphite and improve the thermal conductivity of the composites, the injection molding influences the anisotropy of heat conducting of composites at a large degree.
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Keywords:
- flake graphite /
- orientation /
- polypropylene /
- nylon66 /
- thermal conductivity /
- composites
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