Reusable Nanoporous Al₂O₃-Containing Polyimide Aerogels for Thermal Insulation of Aircraft

Reusable nanoporous polyimide (PI) aerogels are rather promising for highly efficient thermal insulation of future thermal protection systems demanded in aerospace and domestic applications. However, the development of high-performance PI aerogels is limited by their unsatisfactory high-temperature resistance and poor reusability. Herein, an Al 2 O 3 -hybridization strategy toward PI aerogels is demonstrated, and the formed aerogels exhibit a nanoporous structure, unusual reusability, and exceptional high-temperature resistance. Furthermore, the aerogels retain their high-level properties such as the very small changing rates of mass (≤0.3%), shrinkage (≤2.53%), thermal conductivity (≤3%), and bulk density (near-zero difference) even after five cycles of high-temperature assessment (250 °C for 2400 s). The conventional huge heat-induced shrinkage of PI aerogels could be substantially restrained even bearing a high-temperature environment, realizing near-zero thermally insulating degradation, which has an outstanding practical application value. The high-temperature resistance of the aerogel is greatly improved by the Al–O network constructed inside the PI aerogels, and this resistance is retained even after multiple cycles under harsh conditions, ultimately affording superior reusability to PI aerogels for the first time. The high-temperature resistance and ultralow heat-induced shrinkage properties of aerogels, as well as their reusability, make them favorable candidates as thermal protection materials for the future development of aircraft and military.