Development of Polyimide Aerogel Fibers with Ultrahigh Toughness and Thermal Insulation via Dual-Step Imidization and Wet Spinning

Polyimide aerogel fibers (PAFs) are increasingly favored in personal thermal insulation applications for extreme environments; however, the inherent trade-off between thermal insulation and mechanical strength severely limits their practical application. To address this challenge, this work proposes a fabrication strategy for producing PAFs via dual-step chemical imidization and wet spinning based on nonsolvent-induced phase separation (NIPS). Triethylamine (TEA) is introduced to retard nonsolvent-induced phase separation (NIPS) kinetics, forming a uniform porous structure. The dual-step strategy realizes rigid-flexible coupling: preimidization builds a rigid gel skeleton for mechanical enhancement, while postimidization forms a complementary flexible skeleton. Precise draw ratio tuning further optimizes mechanical properties. After optimization, the PAF-Dual fiber achieves high mechanical properties with the stress at break of 59.8 MPa, the strain at break of over 150%, and the outstanding toughness of 63.6 MJ m–3. Additionally, the PAF-Dual fiber exhibits a low thermal conductivity of 0.032 W m–1 K–1, excellent thermal protection over a wide temperature range, and a specific surface area of 124.75 m2 g–1. This work provides a feasible approach for balanced PAFs, promising for wearable extreme-environment protective materials.