Abstract
Lightweight and flexible polyimide foams (PIFs) with superior thermal and acoustic properties were high demand for advanced aerospace and industrial machinery, however, traditional foams could not offer both satisfactory acoustic and thermal insulation simultaneously. In this study, we successfully developed a new class of flexible PIFs by incorporating hyperbranched polysiloxanes (NH2-HBPSi) into ammonium salt oligomer (PAES) through a thermal foaming process. The complex viscosity, micro-foaming behavior of PAES and cell morphology of the resulting PIFs could be precisely controlled by tuning the ratio of NH2-HBPSi/ODA. Significantly, PIFHBPSi-4, a PIF with a NH2-HBPSi loading of 33.3% and exceptional thermal property (T5% exceeded 480 ℃), exhibited a compressive strength of 149 kPa at room temperature (over 100 times higher than commercial PIFs) and a Noise Reduction Coefficient (NRC) of 0.375, which is substantially improved compared to previously reported polyimide composites. Additionally, NH2-HBPSi could form a dense oxide layer at high temperature, impeding the transmission of heat. This allowed PIFHBPSi-4 to withstand a 10-minute exposure to high heat flux of 50 kW/m2 without any significant erosion. These lightweight, flexible, thermally resistant, and acoustically superior hybrid PIFs had the potential to revolutionize applications in high-tech fields like aerospace, acoustics, and aviation.