Hybrid Polyimide Foams with Hyperbranched Organosilicon for High-Temperature Sound Absorption

Lightweight and flexible polyimide foams (PIFs) with superior thermal and acoustic properties are high in demand for advanced aerospace and industrial machinery, however, traditional foams cannot offer both satisfactory acoustic and thermal insulation simultaneously. In this study, we successfully develop a new class of flexible PIFs by incorporating amino-functionalized hyperbranched polysiloxanes (NH2–HBPSi) into ammonium salt oligomer (PAES) through a thermal foaming process. The complex viscosity (η*), microfoaming behavior of PAES and cell morphology of the resulting PIFs are precisely controlled by tuning the ratio of NH2–HBPSi/4,4′-diaminodiphenyl ether (ODA). Significantly, PIFHBPSi-4, a hybrid PIF with a NH2–HBPSi loading of 33.3% and exceptional thermal property (T5% exceeded 480 °C), exhibits a normalized compressive strength of 3.47 kPa/(kg·m–3) at room temperature (over 10 times higher than commercial PIFs) and a noise reduction coefficient (NRC) of 0.375, which substantially improved compared to previously reported polyimide composites. Additionally, NH2–HBPSi can form a dense oxide layer at high temperatures, impeding the transmission of heat. This allows PIFHBPSi-4 to withstand a 10 min exposure to a high heat flux of 50 kW/m2 without any significant erosion. These lightweight, flexible, thermally resistant, and acoustically superior hybrid PIFs have the potential to revolutionize applications in high-tech fields such as aerospace, acoustics, and aviation.