Impact of photochemical aging on high-performance fabrics used in firefighters' protective clothing

High-performance fabrics used in the outer shell of firefighters' protective clothing protect the wearer from severe conditions. These fabrics are exposed to ultraviolet (UV) radiation during service and storage, which may eventually reduce their performance. This study explored the effect of accelerated photochemical aging on three fabrics used in the outer shell of firefighters' protective clothing; they corresponded to aramid copolymer/polybenzoxazole, para-aramid/meta-aramid, and para-aramid/polybenzimidazole fiber blends. The fabric specimens were subjected to irradiances between 0.35 and 1.35 W/m² at temperatures between 40°C and 80°C for up to 600 hours. They were tested for breaking force and apparent water contact angle. Complementary microscopy, chemical, and physicochemical analysis were also performed. The UV-aged para-aramid/polybenzimidazole fabric demonstrated a better breaking force retention compared to the aramid copolymer/polybenzoxazole and para-aramid/meta-aramid fabrics. The considerable reduction in strength observed in the two latter fabrics was associated with fiber breakage. Furthermore, the apparent water contact angle significantly decreased following UV exposure, indicating the potential degradation of the fabric surface finish. On the other hand, no significant changes in the crystallinity index were detected whereas potential decreases in the peak intensity of some chemical functional groups were observed after photochemical aging. These results highlight the significance of material selection in enhancing the long-term performance of fire-protective fabrics and offer insightful information on the photochemical aging of high-performance fabrics.