Research on the preparation and thermal insulation flame retardant properties of polyimide composite aerogel

Polyimide aerogels, known for being lightweight, high-temperature resistant, and low thermal conductivity organic aerogels, have found applications in the aerospace field. However, their flame-retardant properties are not ideal. Therefore, this research uses polyimide gel as the base, with phytic acid and boron nitride nanosheets as reinforcing phases, and incorporates expanded perlite to prepare polyimide composite (PI-AS) aerogels. The aim is to enhance the thermal insulation and flame-retardant properties of polyimide aerogels while reducing environmental pollution. Experiments show that phytic acid can alter the pore structure of polyimide, forming a dense carbon layer after combustion that effectively improves its flame-retardancy. Additionally, it can reduce the thermal conductivity of the aerogel, thereby enhancing its thermal insulation effect. Meanwhile, the addition of boron nitride nanosheets increases the compressive strength of the composite aerogel from 0.12 MPa to 2.04 MPa, significantly improving its mechanical properties. To further elucidate the microscopic mechanisms of thermal insulation and flame-retardancy in this composite aerogel, molecular dynamics theory was employed to investigate the microscopic diffusion process of nitrogen molecules within the composite aerogel under different temperature conditions, confirming the stability of the aerogel structure at low temperatures.