Enhanced thermal conductivity and stability of boron nitride/phenyl silicone rubber composites via surface modification and grain alignment

With the extensive use of high-power electronic appliances, polymer-based thermal insulation composites with excellent thermal properties are utilized in the field of heat management with the aim of improving heat dissipation. Due to the high thermal conductivity and good electrical insulation, boron nitride (BN) is rendered as a superior candidate material for thermally conductive fillers. However, the thermal conduction of the composites is inevitably hampered by the interfacial resistance between BN and the polymer matrix. In this work, BN surface was modified by dopamine hydrochloride (PDA) and phenyltrimethoxysilane to enhance its interface compatibility with the polymer matrix. Meanwhile, by applying pressure to the composites during processing, BN grains inside the composite were well aligned to the direction parallel to the heat flow, thereby improving the through-plane thermal conductivity. When the filler content is fixed at 31 vol%, the thermal conductivity of the phenyl silicone rubber (PVMQ)-based composite prepared from modified BN (mark as M-BN/PVMQ) reaches 1.642 W/(m·K), nearly equal to nine times the value for the pure PVMQ matrix (0.18 W/(m·K)). Furthermore, in a nitrogen atmosphere, the initial decomposition temperature (T5%) reaches 512 °C, 172 °C higher than that of pure PVMQ (340 °C). The improved thermal stability of the composites prepared from modified BN resulted from the enhanced interfacial effect, which was analyzed by thermogravimetric infrared gas mass spectrometry system (TG-IR-GC/MS). The high thermal conductivity and stability enable the M-BN/PVMQ composite a promising material for thermal management.