Degradation of silicone rubbers with different hardness in various aqueous solutions

Durability is one of the remaining challenges for practical application of proton exchange membrane fuel cells. Seals or gaskets around perimeters of each cell in a fuel cell stack are important to prevent leakage of reactant gases, avoiding the decay in utilization of gases and in overall cell performance. In this study, degradation of silicone rubbers, often used as sealing material in fuel cells, with different hardness in various aqueous solutions is investigated. Although the weight loss increases with the increase in hardness, the durability seems enhanced with the increase in hardness, as revealed by the variation of surface morphology and mechanical properties of silicone rubbers before and after exposure to acidic aqueous solutions. It also turns out that the degradation of silicone rubbers can be catalyzed by protons, leading to severe corrosion of materials in strong acidic environment. The results described in this study may provide guidance to evaluation or selection of silicone rubbers as seals for PEMFC applications.