Achieving high thermal conductivity and mechanical reinforcement in ultrahigh molecular weight polyethylene bulk material

Abstract

Exploring pure polymers with high thermal conductivity (TC) is promising to overcome the side effect of conventional thermally conductive polymer-based composites. However, the geometrical shape of high TC polymers was limited to the fibers and/or thin films. Here, we employed a home-made solid-state extrusion (SPE) apparatus to prepare a bulk material of ultrahigh molecular weight polyethylene (UHMWPE) with high TC. The in-plane TC reached 3.30 W/mK, which was 588% higher than that of the high-pressure (HP) molded counterpart (0.48 W/mK). Moreover, the TC of SPE UHMWPE showed an anisotropic ratio as high as 750%, which favored the heat dissipation along the in-plane direction as revealed by infrared thermal imaging. The increased and highly anisotropic TC was attributed to the formation of cylindrical crystals, highly oriented lamellae, as well as the monoclinic form of UHMWPE generated during SPE processing. Benefiting from this unique architecture, the mechanical performance was also greatly intensified, where the ultimate tensile strength increased from 41.6 MPa for HP UHMWPE to 107.7 MPa for SPE UHMWPE. The current study opens up a new pathway to fabricate bulk polymers with simultaneous enhancement of thermal conductivity and mechanical performance, which has great potential for the applications in thermal management fields.