Research on preparation and microscopic mechanism of heat-insulating & flame-retardant EP/PI composite aerogel

Polyimide aerogels, with their lightweight, thermal insulation, and flame-retardant properties, have found extensive applications in aerospace, military, and other fields. However, their use in the building insulation materials market is rare. This paper focuses on polyimide (PI) aerogels and incorporates expanded perlite (EP) of different mesh sizes and qualities to prepare expanded perlite/polyimide (EP/PI) aerogels, aiming to enhance the performance of building insulation materials and reduce energy consumption in buildings. The research results indicate that the incorporation of EP not only protects the aerogel framework from complete destruction and improves its high-temperature stability but also significantly affects the pore distribution of PI aerogels. Specifically, doping a mass of 0.2g of expanded perlite with a mesh size of 80 can increase the specific surface area of PI aerogels by 15 times, effectively increasing the number of pores and the quantity of non-communicating pores in the aerogel, while also reducing the thermal conductivity of PI aerogels by 10 %, thereby hindering heat transfer and enhancing their thermal insulation and flame-retardant properties. To gain a deeper understanding of the thermal insulation mechanism of aerogels, the study combines molecular dynamics principles to analyze the diffusion of nitrogen molecules within the aerogel, thereby elucidating the heat transfer process and explaining the thermal insulation mechanism of EP/PI aerogels. Overall, the findings of this study demonstrate low density, low thermal conductivity, good high-temperature stability, and excellent thermal insulation and flame-retardant effects, indicating significant application potential and socio-economic benefits in building insulation materials.