High thermal conductivity of chain-aligned bulk linear ultra-high molecular weight polyethylene

It is difficult for bulk polymers to be used in the thermal management field because of their low thermal conductivity (TC). Considering that there have been few studies on the enhancement of TC for bulk polymers, we, in this work, used linear ultrahigh molecular weight polyethylene (LUHMWPE), which has a reduced number of branching, rather than conventional UHMWPE to successfully produce a high TC bulk polymer via utilizing solid state extrusion (SSE) to obtain a highly oriented structure. The high orientation of polymer backbone chains parallel to the extrusion direction and the increased crystallinity were responsible for the greatly improved TC. The oriented bulk LUHMWPE's thermal conductivity reached 4.7W/mK, approximately 13 times that of its compression-molded sample, is also higher than the conventional UHMWPE prepared by SSE (3.0W/mK). Moreover, it is found that the final thermal conduction performance of bulk LUHMWPE had a positive correlation with the extrusion draw ratio. The result of scanning electron microscopy shows that a number of nanofiberlike structures were formed during SSE, accounting for the super high tensile strength (120.4MPa) of the bulks. The enhanced thermal conduction performance and high tensile strength make neat LUHMWPE a highly potential candidate to be used in electronic packaging areas.