Flow-Aligned Layered Polyethylene/Graphene Films for Thermal Management

According to the heat conduction theory, the construction of ordered structures is the key to reduce phonon scattering and improve the thermal conductivity (TC) of materials. By using a confined flow-induced orientation effect during stacking hot-pressing, we simultaneously achieve the oriented alignment of ultrahigh-molecular-weight polyethylene (UHPE) chains and graphene nanoplatelets (GNP) in laminated films. The flow-induced orientation can be greatly enhanced by increasing the stacking layers with the maximum Herman’s orientation factors of 0.77 for GNP and 0.68 for UHPE. As a result, the compact oriented structures form three kinds of heat conduction paths (filler-to-filler, matrix-to-matrix, and filler-to matrix) in UHPE/GNP lamellar films with low-interface thermal resistance, thus greatly increasing the in-plane TC from 5.48 to 10.25 W/mK. At the same time, the dual-oriented UHPE/GNP film shows an effective solar–thermal conversion ability that can obtain 57.1 °C surface temperature under 100 mW/cm2 radiation. Therefore, this simple stacking hot-pressing that can realize the synchronous ordering of matrix and filler has good prospects in the large-scale preparation of thermal management materials.