The development of lightweight and highly heat-resistant polyimide foams (PIFs) remains a great challenge in areas of aerospace, military ships, transportation, and industries. Herein, a series of lightweight and highly thermal-resistant copolymerized PIFs are successfully fabricated by the “stepwise heating-holding” thermal foaming of the copolymerized polyester ammonium salts (C-PEAS), using 3,3′,4,4′-benzophenone tetracarboxylic acid dianhydride (BTDA) and 2,3,3′,4′-biphenyl tetracarboxylic acid dianhydride (α-BPDA) as codianhydride, and p-phenylenediamine (PDA) as diamine. The introduction of α-BPDA increases the rigidity of PI molecule chains and foamability of C-PEAS, and significantly improves the heat resistance of PIFs. The resultant copolymerized PIFs exhibit ultra-low densities (<10 kg m−3), excellent heat resistance (Tg ranging from 351.2 °C to 405.6 °C), and high thermal stability. Moreover, they possess high flame retardancies (LOI>44 %) and low thermal conductivities (as low as 0.0463 W m−1 K−1 at 20 °C and no more than 0.0825 W m−1 K−1 at 200 °C), demonstrating their excellent thermal insulation properties in a wide temperature range. After the continuous heating at 200 °C for 40 min, the upper surface of PIFs present low average temperatures less than 60 °C. Additionally, the copolymerized PIFs exhibit remarkable acoustic properties with average acoustic absorption coefficients above 0.6 and noise reduction coefficients (NRC) above 0.3. Therefore, the lightweight and highly heat-resistant copolymerized PIFs show great application potentials in the extreme environments of aerospace, military ships, transportation, and industries.

中文翻译：

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轻质、高耐热的共聚酰亚胺泡沫，具有卓越的隔热性和吸音性


轻质、高耐热的聚酰亚胺泡沫 （PIF） 的开发在航空航天、军舰、运输和工业领域仍然是一项巨大挑战。在此，使用 3,3′，4,4′-二苯甲酮四羧酸二酐 （BTDA） 和 2,3,3′，4′-联苯四羧酸二酐 （α-BPDA） 作为钊酐，对苯二胺 （PDA） 作为二胺，通过共聚聚酯铵盐 （C-PEAS） 的“逐步加热保持”热发泡成功制备了一系列轻质且高耐热性的共聚 PIF 和对苯二胺 （PDA） 作为二胺。α-BPDA 的引入增加了 PI 分子链的刚度和 C-PEAS 的发泡性，并显着提高了 PIF 的耐热性。所得的共聚 PIF 表现出超低密度 （<10 kg m-3）、优异的耐热性（Tg 范围为 351.2 °C 至 405.6 °C）和高热稳定性。此外，它们具有高阻燃性 （LOI>44 %） 和低导热率（20 °C 时低至 0.0463 W m-1 K-1,200 °C 时不超过 0.0825 W m-1 K-1），在较宽的温度范围内表现出优异的隔热性能。在 200 °C 下连续加热 40 分钟后，PIF 的上表面呈现低于 60 °C 的低平均温度。 此外，共聚 PIF 表现出卓越的声学性能，平均吸声系数高于 0.6，降噪系数 （NRC） 高于 0.3。因此，轻质、高耐热的共聚 PIF 在航空航天、军舰、交通和工业的极端环境中显示出巨大的应用潜力。