Rotational stress-induced shish-kebab governs the balance of enhanced thermal conductivity and mechanical performance of high-density polyethylene (HDPE) / boron nitride (BN) composites via axial hot compression

Abstract

Polymer-based composites with high BN sheets loadings have potential to improve thermal conductivity without compromising mechanical performance. In this work, a balanced enhancement in both thermal conductivity and tensile strength were achieved using rotational shear followed by axial hot compression. For neat HDPE matrix, the highly oriented shish-kebab structures induced by shear field improved tensile strength from 20.4 MPa to 80.9 MPa, compared with unsheared specimens. The in-plane thermal conductivity of sheared HDPE/BN composite was 25.0% higher than the unsheared one. Axial hot compression resulted in denser crystal and oriented fillers, leading to a 63% increase in tensile strength while simultaneously increasing thermal conductivity in both in-plane and out-plane directions. This work has utilized rotation shear and axial hot compression to manufacture HDPE/BN composites with effective two-way thermal conductivity and higher tensile strength. The excellent thermo-mechanical properties mean a longer service time and less replaced frequency of material under extreme operating conditions. The two-step methods provide a key information for the preparation of composites with balanced mechanical properties and thermal conductivity.