Analysis of the aging mechanism and life evaluation of elastomers in simulated proton exchange membrane fuel cell environments

Abstract

This paper studies the aging mechanism of elastomeric gaskets made from silicone rubbers in simulated proton exchange membrane fuel cells (PEMFCs) in humid, acidic, and high-temperature environments. The changes in the surface morphology are observed using optical microscopy. Attenuated total reflection Fourier transform infrared spectroscopy (AFT-FTIR) and X-ray photoelectron spectroscopy (XPS) are used to investigate the changes in the chemical molecular structure. The stress relaxation test is conducted to characterize the decay process of the mechanical properties. The results indicate that cracks appear on the surface and that the aging mechanism is mainly due to decomposition in the backbone and hydrolysis of the crosslinking. The stress relaxation modulus decreases as the acid concentration increases, which suggests a decrease in elasticity and an increase in brittleness. A master curve that relates time and concentration is constructed. Based on this inference, the experimental time can be shortened by about four times.

Keywords

• degradation mechanism
• silicone
• stress relaxation
• fuel cell
• lifetime