Moisture barriers used in firefighters' protective clothing: Effect of accelerated thermal aging on their mechanical and barrier performance

Abstract Moisture barriers are an essential component in firefighters' protective clothing as they allow water vapor to exit and prevent liquids from entering into the garment. However, they may be sensitive to thermal aging. This study investigates the effect of accelerated thermal aging at temperatures between 95 and 240°C on three different moisture barriers used in firefighters' protective clothing. Variations in their tear force, water vapor transmission rate (WVTR), and apparent contact angle were observed after thermal aging. These variations were influenced by factors such as the base fabric structure, fiber content, adhesive characteristics, and presence of an additional flame‐resistant polyurethane coating on top of the expanded polytetrafluoroethylene membrane. Adhesive degradation and delamination were observed in one moisture barrier, whilst different extents of base fabric degradation occurred in all three of them, leading to tear force reduction. Depending on the moisture barrier and aging temperature, the membranes experienced crack formation or pore closure, which affected the WVTR. The water‐repellent finish on the fabric side degraded in two moisture barriers but was not affected in the other. These findings highlight the importance of considering the constitutive materials and the structure of moisture barriers to understand their aging behavior and improve firefighters' safety.