Degradation of silicone rubber under compression in a simulated PEM fuel cell environment

Long-term stability and durability of gaskets in Polymer Electrolyte Membrane (PEM) fuel cell is critical to both sealing and the electrochemical performance of the fuel cell. In this paper, the time-dependent chemical and mechanical degradation of silicone rubber, which is one of the potential gasket materials for PEM fuel cells, was investigated. Test samples were subjected to a constant compressive load to simulate the actual loading on seals and soaked in a simulated PEM fuel cell environment. Based on actual PEM fuel cell operation, two temperatures 60 degrees C and 80 degrees C were selected and used in this study. The optical microscopy was used to reveal the topographical changes on the sample surface. Atomic absorption spectrometer analysis shows that silicon, calcium and magnesium were leached from the material into the soaking solution. Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy was employed to study the surface chemistry of the silicone rubber before and after exposure to the test environment. The ATR-FTIR results indicate that the surface chemistry changed significantly via de-crosslinking and chain scission in the backbone for the material over time. The microindentation test was used to assess the change of mechanical properties of the material before and after exposure to the environment. It was found that the mechanical properties of the silicone rubber material changed significantly and both the temperature and the exposure time have direct effect on the stiffness of the material. (c) 2007 Elsevier B.V. All rights reserved.