Ali Mehamed, Sobolciak Patrik, Krupa Igor, Abdala Ahmed
Chemical Engineering Program, Texas A&M University at Qatar, Doha P.O. Box 23874, Qatar.
Center of Advanced Materials, Qatar University, Doha P.O. Box 2713, Qatar.
Polymers (Basel). 2023 Aug 16;15(16):3426. doi: 10.3390/polym15163426.
Emergent heat transfer and thermal management applications require polymer composites with enhanced thermal conductivity (κ). Composites filled with non-spherical fillers, such as hexagonal boron nitride (hBN) and Graphite (Gr), suffer from processing-induced filler orientations, resulting in anisotropic κ, commonly low in the through-plane direction. Here, the effects of extrusion and compression molding-induced orientations on κ of hBN- and Gr-filled polyethylene composites were investigated. The effect of extrusion on the hBN orientation was studied using dies of various shapes. The shaped extrudates exhibited hBN orientations parallel to the extrusion flow direction, which prompted additional hBN orientation during compression molding. κ of the composites produced with shaped extrudates varied from 0.95 to 1.67 W m K. Pelletizing and crushing the extrudates improved κ, by exploiting and eliminating the effect of extrusion-induced hBN orientations. Gr-filled composites showed better κ than hBN composites due to the higher intrinsic conductivity and bigger particle sizes. A maximum κ of 5.1 and 11.8 W m K was achieved in composites with oriented hBN and Gr through a thin rectangular die and stacking the sheets to fabricate composites with highly oriented fillers.
紧急热传递和热管理应用需要具有增强热导率（κ）的聚合物复合材料。填充有非球形填料（如六方氮化硼（hBN）和石墨（Gr））的复合材料会因加工过程中填料的取向而导致热导率呈各向异性，通常在垂直于平面方向上较低。在此，研究了挤出和压缩成型诱导的取向对hBN和Gr填充的聚乙烯复合材料热导率的影响。使用各种形状的模具研究了挤出对hBN取向的影响。成型挤出物呈现出与挤出流动方向平行的hBN取向，这在压缩成型过程中促使hBN产生额外的取向。用成型挤出物生产的复合材料的热导率在0.95至1.67 W m K之间变化。通过利用和消除挤出诱导的hBN取向的影响，将挤出物造粒和粉碎提高了热导率。由于Gr的本征电导率更高且粒径更大，Gr填充的复合材料显示出比hBN复合材料更好的热导率。通过一个薄的矩形模具使hBN和Gr取向，并将片材堆叠以制造具有高度取向填料的复合材料，在这些复合材料中分别实现了5.1和11.8 W m K的最大热导率。
