Organic–Inorganic Hybrid Isocyanate-Based Polyimide Foams with Excellent Fire Resistance and Thermal Insulation Performance

Due to the formation of urea byproducts in the preparation process, isocyanate-based polyimide foams (PIFs) are flammable, and fire-resistant properties need further improvement. In this paper, a simple and low-cost organic–inorganic hybrid method was proposed to successfully construct high-performance fire-retardant isocyanate-based PIF/SiO2 composites. With the increase of SiO2 content, the fire resistance of PIF/SiO2 composites was significantly improved. Cone calorimetry test suggested that the peak heat release rate (PHRR) of the PIF/SiO2-8 composite was reduced by 58.0% than that of the neat PIF. Moreover, the limiting oxygen index (LOI) value for the composite was as high as 59.68%, exceeding the LOI values of all previously reported isocyanate-based PIFs and some PIFs prepared using the powder foaming method. Meanwhile, the PIF/SiO2 composites exhibited outstanding thermal insulation performance at high temperatures due to their excellent fire resistance. This work provides a promising approach for constructing isocyanate-based PIF with superior flame-retardant performance and is conducive to broaden the scope of their applications in aerospace, architecture, and other fields.