Double-network polyimide/silica aerogel fiber for thermal insulation under extremely hot and humid environment

Aerogel fibers display good flexibility, low density and high porosity, making them highly promising as wearable thermal-insulating textiles. However, the inferior thermal insulating property in hot and humid environment resulting from the poor thermal stability and water penetration hampers their use in harsh environments. Herein, we report a double-network organic/inorganic aerogel fiber for thermal insulation under extremely hot and humid environment prepared by co-gelation and freezing-spinning technique. Through the co-gelation strategy, a homogeneous organic/inorganic poly(amic acid)/SiO2 (PAA/SiO2) gels can be obtained, benefiting for the stable spinning process. The resultant polyimide/silica (PI/SiO2) aerogel fibers with unique organic/inorganic double-network structure display good mechanical strength, exceptional thermal stability (up to 500 °C) and low thermal conductivity (75.6 mW m−1 K−1 at 350 °C). Furthermore, the PI/SiO2 aerogel fabrics reveal hydrophobicity and can effectively prevent thermal transfer in hot and humid environment with thermal conductivity of 58.8 mW m−1 K−1 at 80 °C and relative humidity of 100%, about 60% lower than that of silica aerogels. It is expected that such PI/SiO2 aerogel fibers/fabrics will be applied as a novel textile for thermal insulation in hot and humid environments.