Polyimide-silica composite aerogel microspheres for thermal insulation and flame retardancy

Abstract

This study develops polyimide-silica composite aerogel microspheres (PIA@SiO2) reinforced with phytic acid (PA) to address the synergistic requirements for lightweight, low thermal conductivity, and high flame retardancy in thermal insulation and flame-retardant materials across industries such as aerospace and advanced building materials. Using the reverse emulsion method combined with the sol-gel process, tetraethyl orthosilicate was used as the silica source and polyamic acid as the precursor to prepare silica-coated polyimide (PI) microspheres, while PA was introduced to achieve phosphorus-based flame-retardant functionality. The effects of PA and PI on the microsphere properties were thoroughly investigated by adjusting their concentrations. Experimental results showed that the incorporation of PA optimizes the pore structure of the aerogel microspheres to inhibit gas-phase heat transfer and the carbon layer formed after combustion prevents the penetration of flammable gases, thereby slowing down the degradation of the microspheres. PI crosslinking forms a PI-SiO2 crosslinked network with SiO2 and the strong organic-inorganic interface interaction promotes uniform heat dispersion, thereby ensuring the thermal insulation performance of the aerogel microspheres; simultaneously, the results clearly demonstrate that microspheres containing 10% PA and 10% PI exhibit excellent thermal stability, It is predicted that the material can reach the V0 rating, and long-term thermal insulation capability.