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

Firefighters' protective clothing rely on moisture barriers to safeguard against liquid ingress while enabling sweat evaporation for comfort and safety. However, these moisture barriers can degrade over time, jeopardizing firefighters' safety. Existing evaluation methods, primarily visual inspection, are inadequate for assessing moisture barrier integrity in service. This study examines the effect of accelerated hydrothermal aging on the tear force, water vapor transmission rate (WVTR), and apparent contact angle in three moisture barrier models used in firefighter protective clothing. The moisture barriers studied varied in composition, structure, and base fabric fiber content. Results revealed that moisture barriers' responses to aging are influenced by factors, such as fabric structure, adhesive configuration, finish, and the presence of additional coatings. The hardening of the adhesive layer between the ePTFE membrane and the base fabric was observed in two of the moisture barriers, leading to a slight tear force reduction. Two of the moisture barriers also experienced crack and pit formation on the membrane side, which affected the WVTR. The water-repellent finish on the fabric side degraded in one moisture barrier. Understanding these complex behaviors is essential for predicting the long-term moisture barrier performance and enhancing firefighter safety.