Flame-retardant and thermal-protective polyimide-hydroxyapatite aerogel fiber-based composite textile for firefighting clothing

Firefighting protective clothing is an essential equipment for firefighters that can provide protection from all kinds of thermal hazards and prevent burn injuries. However, it is still a challenge to develop lightweight firefighting clothing without compromising their excellent fire-resistant and thermal-protective performance. In this study, we report a novel polyimide aerogel fiber-based double-layer smart textile comprising of flame-retardant outer layer (ambient-side) with excellent fire resistance and phase-changeable inner layer (next to skin side) with thermal-regulating function, achieving comprehensive flame-retardant and thermal-protective function. The polyimide-hydroxyapatite-reduced graphene oxide (PI-HAP-rGO) aerogel fabric (outer layer) acquires 54.7% and 70.0% reduction of peak heat release rate compared with that of pure PI aerogel fabric and commercial aramid fabric, respectively, exhibiting excellent fire resistance. The phase-changeable polyimide-hydroxyapatite/eicosane (PI-HAP/C20) fabric (inner layer) with high melting enthalpy of 193.2 J g(-1) can delay the temperature rise by thermal buffering effects during the phase change process, endowing cool somatosensory temperature for firefighters. Consequently, the double-layer smart textile can extend the time (280.0 s) to pain threshold of human skin, much longer than that of the commercial aramid fabric (101.0 s) and glass fiber fabric (56.5 s), which exhibits huge potential for next-generation firefighting clothing.