α-Keratin dehydration-analogous nanofiber aggregation engineering of aramid aerogels for integrated mechanical and thermal protection

Lightweight materials with outstanding mechanical durability and heat attenuation play an indispensable role in personnel safeguard. Aerogels are excellent insulation materials while presenting low strength, posing a challenge to integrated protection. Herein, a dehydration-induced aggregation strategy is proposed to reinforce lamellar aramid nanofiber aerogels through impregnation in polyvinyl alcohol (PVA) solution followed by hot-pressing. PVA shrinkage facilitates synergistic fiber crosslinking and sheet densification in the resulting AFPA aerogels, achieving extraordinary specific tensile modulus (1143.2 MPa cm 3  g −1 ) and toughness (2557 kJ m −3 ). Both experiments and simulations demonstrate that the aggregated fibrous network extends fracture period by re-orientation and crack deflection, which enables AFPAs 220 % and 162 % greater specific puncture energy than woods and leathers. Benefiting from the lamellar porous skeleton with low PVA content, AFPAs not only prevent the invasion of heat and fire, but maintain 95 % of initial strength and robust impact dissipation after heat treatment at 300 °C. With a low thermal conductivity of 31 mW m −1  K −1 , AFPAs provide better thermal comfort from −106 to 150 °C than duck down with only 31 % of its thickness. This integrated protection system can be re-established by a solvent-mediated recycling approach, promoting their sustainable applications across fire-fighting, anti-seismic building, and aircrafts.