Effect of water on life prediction of liquid silicone rubber seals in polymer electrolyte membrane fuel cell

Liquid silicone rubber (LSR) is a popular gasket or seal material and is also promising for sealing applications in polymer electrolyte membrane fuel cell (PEMFC). The durability of the LSR gasket/seals in PEMFC is one of the major issues in commercialization of PEMFC. As there are water and humidity inside PEMFC and polymers such as LSR generally exhibit stress relaxation property, it is important to understand the effect of water on the compression stress relaxation of LSR. Our test results show that water has no influence on the stress relaxation in the beginning, but it accelerates the relaxation after a certain time. Higher temperature makes this transition occurs earlier. Further studies reveal that water can diffuse into LSR and exists as free water molecules. It may attack the backbones of the polymer and thus accelerate the stress relaxation. High temperature tends to aggravate the attack of water to the polymer chains. The attack coexists with the thermal degradation of the LSR.

► Water accelerates the relaxation of LSR seals.
► Higher temperature makes this transition occurs earlier.
► Water can diffuse into LSR and exists as free water molecules.
► Water may attack the backbones of the polymer.
► High temperature tends to aggravate the attack of water to the polymer chains.