Rigid polyimide foams (PIFs) with excellent compressive and thermal properties were fabricated by thermal foaming of polyester ammonium salts (PEAS) precursors which were terminated by 5-norbornene-2,3-dicarboxylic anhydride (NA). The melt viscosities of PEAS precursors were found essential to obtaining PIFs with high closed cell ratios and improved interactions between foam cells, which were indispensable to improving mechanical properties. The room temperature compressive strength and compressive modulus of PIF (density: 146.3 kg m^–3) with four repeating units reached 1.55 and 23.3 MPa, which were 7 and 9 times higher than that of PIF-∞ (230.9 kg m^–3), respectively. Furthermore, the room temperature compressive strength of PIFs with foam densities of 358.3 kg m^–3 reached 9.79 MPa. The PIFs demonstrated outstanding thermal properties with initial thermal degradation and glass transition temperatures higher than 450 and 290 °C, respectively. The thermal conductivities of PIFs fell in a range of 0.071–0.073 W m^–1 K^–1, which showed promising applications in the fields of aerospace, aeronautics, and marine use as high temperature-resistant structural materials.

中文翻译：

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具有优异抗压性能的硬质聚酰亚胺泡沫的制备

通过对以 5-降冰片烯-2,3-二羧酸酐 (NA) 封端的聚酯铵盐 (PEAS) 前体进行热发泡制备具有优异压缩和热性能的硬质聚酰亚胺泡沫 (PIF)。发现 PEAS 前体的熔体粘度对于获得具有高闭孔率和改善泡沫孔之间相互作用的 PIF 至关重要，这对于提高机械性能是必不可少的。^{具有四个重复单元的PIF（密度：146.3 kg m -3} ）的室温抗压强度和压缩模量分别达到1.55和23.3 MPa，分别是PIF-∞（230.9 kg m ^-3）的7倍和9倍，分别。^{此外，泡沫密度为 358.3 kg m –3}的 PIF 的室温抗压强度达到 9.79 兆帕。PIF 表现出出色的热性能，初始热降解和玻璃化转变温度分别高于 450 和 290°C。PIFs的热导率在0.071~0.073 W m ^-1 K ^-1范围内，作为耐高温结构材料在航天、航空、海洋等领域具有广阔的应用前景。