Long-term stability and durability of gaskets in Proton Exchange Membrane (PEM) fuel cell are critical to both sealing and the electrochemical performance of the PEM fuel cell. In this paper, the time-dependent chemical degradation of the silicone rubber, which is one of the potential gasket materials for PEM fuel cells, is studied in a simulated PEM fuel cell environment and four accelerated durability test (ADT) media for short-term aging tests at 70 degrees C. The weight loss of samples is monitored. The optical microscopy is used to show the topographical changes on the sample surface. Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) are employed to study the surface chemistry of the samples before and after exposure to the test environments over time. The results show that the weight loss increases with the exposure time. The optical microscopy reveals that the surface conditions of the samples changes from initially smooth to rough, crack appearance and finally crack propagation. The ATR-FTIR and XPS results show that the surface chemistry changes significantly via de-crosslinking and chain scission in the backbone for the samples exposed to the environments over time. (C) 2012 Published by Elsevier B.V.