Thermal aging of high‐performance fabrics used in the outer shell of firefighters' protective clothing

Abstract High‐performance fibers are known for their exceptional specific strength and resistance to various hazardous conditions, including fire. However, the long‐term performance of these fibers when exposed to convective heat has rarely been reported. This study investigated the accelerated thermal aging behavior of three high‐performance fabrics of different blends of inherently flame‐resistant high‐performance fibers: copolymer of aramids (Technora®)/polybenzoxazole (PBO); para‐aramid/meta‐aramid; and para‐aramid/polybenzimidazole (PBI). Fabric specimens were thermally aged for up to 1200 h at temperatures ranging from 90 to 320°C. While all three fabrics experienced losses in the breaking force, the Technora®/PBO fabric displayed the best strength retention, despite the complete disappearance of the Technora® fiber crystallinity after aging at 320°C for 1200 h. The para‐aramid/PBI blended fabric showed signs of competing aging processes at high temperatures. An increase in the fabrics' crystallinity and evidence of chain scission were observed after thermal aging. Additionally, degradation in the fabric's water‐repellent finish was observed. The findings of this study will contribute to the development of more durable and safer protective gear, particularly for high‐risk activities like firefighting.