关键词: Polymethylacrylimide, Heat transfer, Mechanical properties, Boron nitride, Composites

Abstract: Constructing a three-dimensional (3D) network of fillers with high thermal conductivity is considered to be an effective strategy to obtain ideal thermal management materials (TMMs). However, 3D filler network is often disrupted by the subsequent processing and forming processes, and it is difficult to incorporate high levels of fillers into lyophilized aerogels, which is a key factor limiting their widespread use. In this work, boron nitride@polymethylacrylimide/epoxy (BN@PMI/EP) composites with a stable 3D BN network were prepared by freeze-drying and hot-pressing. A water-soluble copolymer quaternary ammonium salt has been synthesized by the solution polymerization. A BN@PMI aerogel was obtained by the freeze-drying of ammonium salt and BN solution and thermal imidization. The BN@PMI aerogel has a six-membered imine ring structure that can be loaded with a high content of BN, which ensures the stability of the 3D BN network structure and facilitates the subsequent impregnation of EP in vacuum, which is one of the innovations of this work. The stable and complete 3D BN network leads to the enhancement of thermal conductivity, and the out-of-plane and in-plane thermal conductivities of BN@PMI/EP reach 1.21 W·m^-1·K^-1 and 2.76 W·m^-1·K^-1 at a BN mass loading of 40%, respectively. Meanwhile, the excellent mechanical properties and results of finite-element simulation and actual experiments confirm that BN@PMI/EP is a potential TMM.

Key words: Polymethylacrylimide, Heat transfer, Mechanical properties, Boron nitride, Composites