Li Jianwei,Yu Ni,Jing Zhanxin,He Xinhai,Shi Xuetao,Zhang Guangcheng
This work provides a method for fabricating rigid polyimide foams via thermal foaming method of nadimide-end-capped polyester-amine oligomer (NPEAO) precursor particles, which were synthesized by reaction of benzophenone-3,3′,4,4′-tetracarboxylic dianhydride and cis -5-norbornene-endo-2,3-dicarboxylic anhydride (NA) with different diamines. The foaming mechanism of the rigid PI foams was systematically investigated. The experiment demonstrates that the pre-treatment of the NPEAO precursor particles and foaming temperature are two pivotal factors that determine the foaming processes. The densities of the prepared rigid PI foams are mainly in the range of 40–200 kg m −3 . Moreover, the density and morphology of the PI foams can be effectively controlled by adjusting these two factors. Besides, the obtained rigid PI foams present excellent mechanical and thermal properties, specifically, the flexural and compressive strength reaches as high as to 1.42 MPa and 0.47 MPa, respectively, with the density of 0.076 g cm −3 , which are superior to common PI foams and aerogels that of reported in the literature. Therefore, these superior mechanical and thermal properties make obtained rigid PI foams promising candidates as structural materials in the advanced manufacturing industry.
Yang Xu,Luwei Bo,Yandong Wang,Haocheng Xu,Xiaolin Jiang,Zhaobo Wei,Kai Xi
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.
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