The Orientation of BN Nanosheet in Polyimide to Improve the Thermal Conductivity of Epoxy Resin

Abstract

Epoxy resin is widely used in DC converter valves, DC bushings, and gas-insulated switches due to its excellent insulation and mechanical properties. Since epoxy resin demonstrates low thermal conductivity and toughness, epoxy resin-impregnated power equipment exhibits poor heat dissipation capability and is easy to crack under mechanical stress. Therefore, research on epoxy resins with high thermal conductivity has received extensive research attention. In this article, a directional freezing method is used to build a thermally conductive network with polyimide and boron nitride nanosheets (BNNS) as the skeleton. The thermally conductive network is immersed in the epoxy resin to improve the thermal conductivity of the epoxy resin matrix. The microstructure of PI/BNNS aerogel and epoxy resin/polyimide interpenetrating networks (IPNs) was observed under the electron microscope. The thermal conductivity and dielectric properties of the composite material were tested. The directional growth of ice crystals contributes to the highly orientated tubular pores in the IPNs aerogel. The BNNS aligned along with the polyimide effectively improves the thermal conductivity of the epoxy resin, reaching a thermal conductivity of 0.745W·m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> ·K <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> , which is 5 times compared to pure epoxy resin with the BNNS content of 15wt%.