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<p>Supercritical carbon dioxide (sCO<sub>2</sub>) foaming offers a green and efficient route to fabricate high-performance polyimide (PI) foams, which are coveted for their exceptional thermal stability and intrinsic flame retardancy in advanced fields. However, the high glass transition temperature and low melt strength of PIs present significant challenges, leading to a narrow foaming window, poor cell formation, and low expansion ratios. To address these limitations, we developed a strategy that enhances melt strength and broadens the foaming process window by constructing a controllably slightly cross-linked network in polyimides via precise molecular weight modulation of a maleic anhydride-terminated network precursor. By designing and synthesizing this precursor with molecular weight regulated by feeding ratios, and subsequently inducing thermal crosslinking under hot-pressing, we systematically regulated the molecular weight between cross-link points (<i>M</i><sub>c</sub>) and obtained slightly cross-linked materials. This approach enabled the successful production of a series of PI foams via sCO<sub>2</sub> foaming process, which exhibit a broad foaming window, a homogeneous cell structure, and a significantly enhanced expansion ratio (10.51)—representing a 6.11-fold increase over the linear PI. Furthermore, the resulting slightly cross-linked polyimide foam exhibits excellent mechanical properties, thermal insulating properties, and flame-retardant properties, highlighting its broad application potential in fields requiring lightweight, high-performance materials, such as low-altitude economy and humanoid robots.</p>

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High expansion ratio polyimide foam prepared by sCO2 process through precise control of molecular weight between cross-link points

  • 期刊论文

  • 发表日期：

    2026年7月23日

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  • Chuying Li,
  • Yanwei He,
  • Jiahui Liu,
  • Huifa Meng,
  • Xueyi Yu,
  • Xiaoying Xing,
  • Xing Kang,
  • Yinghua Sha,
  • Kaijin Chen,
  • Yanming Chen,
  • Siwei Liu,
  • Ying Shi,
  • Yi Zhang

摘要

Supercritical carbon dioxide (sCO2) foaming offers a green and efficient route to fabricate high-performance polyimide (PI) foams, which are coveted for their exceptional thermal stability and intrinsic flame retardancy in advanced fields. However, the high glass transition temperature and low melt strength of PIs present significant challenges, leading to a narrow foaming window, poor cell formation, and low expansion ratios. To address these limitations, we developed a strategy that enhances melt strength and broadens the foaming process window by constructing a controllably slightly cross-linked network in polyimides via precise molecular weight modulation of a maleic anhydride-terminated network precursor. By designing and synthesizing this precursor with molecular weight regulated by feeding ratios, and subsequently inducing thermal crosslinking under hot-pressing, we systematically regulated the molecular weight between cross-link points (Mc) and obtained slightly cross-linked materials. This approach enabled the successful production of a series of PI foams via sCO2 foaming process, which exhibit a broad foaming window, a homogeneous cell structure, and a significantly enhanced expansion ratio (10.51)—representing a 6.11-fold increase over the linear PI. Furthermore, the resulting slightly cross-linked polyimide foam exhibits excellent mechanical properties, thermal insulating properties, and flame-retardant properties, highlighting its broad application potential in fields requiring lightweight, high-performance materials, such as low-altitude economy and humanoid robots.