Ultralow shrinkage polyimide hybrid aerogel composite enhanced with organic fibers for thermal protection

Abstract

Polyimide PI aerogels possess a rather potential in thermal protection material for aircraft, owing to their low thermal conductivity, high thermal stability, and low bulk density. However, the large shrinkage of pure PI aerogels is still a challenge in the complete preparation process. Herein, a kind of PI hybrid aerogel composite was prepared successfully by introducing polyurethane fiber as the reinforcing agent. The aerogel composite could realize the enhancement for the pure PI aerogels from a micro/macroscopic perspective, ultimately ensuring the ultralow shrinkage rate of 3.52%. Due to the inhibition of the shrinkage characteristic, the aerogel composite obtained achieved excellent thermal insulation, especially retaining a low temperature of 40.7°C despite the hot surface temperature reached up to 150°C. Besides, the lightweight low‐density, exceptional flame resistance, and self‐extinguishing properties were reflected from PI hybrid aerogel composite constructed, including the outstanding hydrophobic feature (water contact angle of 120°). The PI hybrid aerogel composite as prepared may be used for the thermal management of aircraft in a great measure, illustrating the feasible strategy of fabricating PI‐based aerogel composites.

Piperazine as a Water-Solubilizing Agent for Cross-Linking and Mechanical Enhancements in Freeze-Dried PI Aerogels

“…Due to the unique structure of PI aerogels, their compressive behavior exhibits a distinct three-stage deformation mechanism. 42 In the initial stage (0%−10% strain), the material demonstrates an approximately linear elastic response, indicating reversible deformation of its internal porous structure. Within the strain range of 10%−60%, the deformation of the aerogel material continues, and the sample can almost return to its original state upon unloading.…”

“…Due to the unique structure of PI aerogels, their compressive behavior exhibits a distinct three-stage deformation mechanism . In the initial stage (0%–10% strain), the material demonstrates an approximately linear elastic response, indicating reversible deformation of its internal porous structure.…”