Lightweight, strong, and super-thermal insulating polyimide composite aerogels under high temperature

High-performance thermally insulating materials is highly desirable for many applications in which heat transfer should be strictly restricted. Traditional organic or inorganic insulation materials are limited by either poor thermal stability or mechanical brittleness. Here, SiO2 nanoparticles crosslinked polyimide aerogels synthesized by one-pot freeze-drying are presented, which show excellent mechanical properties and super-insulating behavior in a wide temperature range. The highly porous structure of the aerogel and nanosized components benefit the significant reduction of thermal conductivity through inhibiting gas conduction and imparting interfacial thermal resistance, respectively. The PI/SiO2 composite aerogel with a density of 0.07 mg cm−3 can achieve a low thermal conductivity of 21.8 mW m−1 K−1, which is lower than the most common super-insulating criterion (25 mW m−1 K−1). More importantly, the PI/SiO2 aerogel exhibits good thermal insulation performance at elevated temperatures, with a thermal conductivity still lower than 35 mW m−1 K−1 even at 300 °C. Therefore, the mechanically strong and super-insulating PI/SiO2 composite aerogels are promising candidates for practical thermal insulation applications.