Abstract:
Polyimide (PI) nanofiber aerogels with mass fraction of 0.3%‒0.7% were prepared by optimized template freeze-drying method at different freezing temperatures (−50, −20, 0℃). The microstructure, thermal conductivity, mechanical properties, dielectric properties and sound absorption properties of the aerogels were investigated. The results show that the maximum size of PI nano-fiber aerogel could reach 50 cm×50 cm×1 cm. The pores of PI nano-fiber aerogel fibers prepared at −20 ℃ were smaller and the fiber distribution was more uniform. Under different PI mass fractions, the density of PI nano-fiber aerogel was (3~7)×10
−3 g·cm
−3, and the thermal conductivity was in the range of 0.023‒0.029 W·m
−1·K
−1, the maximum compressive strain was greater than 90%, the linear elastic modulus was in the range of 1~3 kPa, the lowest dielectric constant at 1 MHz was 2.65, and the average acoustic absorption coefficient at 4 000‒6 400 Hz was 0.86. The PI nanofiber aerogel had the advantages of ultra-light weight, low thermal conductivity, good flexibility and resilience, low dielectric and high sound absorption.