Robust, Ultralight Polybenzimidazole Nanofiber‐Based Composite Foaming Mat for Enhanced Comfort and Protection in Firefighting Clothing

ABSTRACT Conventional firefighter clothing offers good thermal protection but is severely hindered by its heavy weight, low air and moisture permeability, and low porosity, leading to very poor wearing comfort. The incorporation of per‐ and fluorinated alkyl substances (PFAS) also imposes health risks for firefighters and the environment. Here, a non‐fluorinated superhydrophobic, polybenzimidazole (PBI) nanofiber‐based composite foaming material featuring a highly porous architecture enriched with closed‐cell pores and a nanofiber structure is developed. The lightweight and durable nanofiber foamed composite mat (NFCM) can effectively enhance the protective performance and wear comfort of thermal insulating materials for firefighting garments and other special environments. This NFCM exhibits ultralow thermal conductivity of 0.013 W·m −1 ·K −1 and low density of 0.037 g/cm 3 , with a limiting oxygen index (LOI) of 38%. To the best of our knowledge, such a combination of properties has not yet been reported in the literature. The superhydrophobic feature of NFCM effectively prevents liquid infiltration even under boiling water. Under simulated harsh external environments (e.g., boiling water, ∼300°C thermal environment, and ‐15°C freezing condition), it maintains internal temperatures of 52°C, 182°C, and 15°C, respectively. The NFCM also demonstrates exceptional wearing comfort, featuring good air and moisture permeability.