Chemical and mechanical degradation of silicone rubber under two compression loads in simulated proton‐exchange membrane fuel‐cell environments

Abstract

Long‐term chemical and mechanical stability of gaskets in proton‐exchange membrane (PEM) fuel cells is critical to the sealing and normal operation of these fuel cells. In this study, the chemical and mechanical degradation of a silicone rubber was investigated. Two compression loads and two simulated environments were used. The weight change of sample was monitored. Optical microscopy was applied to observe the morphological changes on the specimen surface. Attenuated total reflection (ATR)–Fourier transform infrared (FTIR) spectroscopy and X‐ray photoelectron spectroscopy (XPS) were used to investigate the chemical changes on the surface of specimens after exposure to the simulated solutions and subjection to compression loads over time. A compression stress‐relaxation test was used to elucidate the stress‐relaxation property changes of the specimens after exposure to the simulated fuel‐cell environments and the compression loads. Optical microscopy showed that the surface morphology of the specimens changed from initially smooth to slightly rough followed by crack initiation and finally propagation. The ATR–FTIR and XPS results indicate that the surface chemistry of the specimens significantly changed via decrosslinking and chain scission after exposure to the simulated environments and compression loads over time. The compression stress‐relaxation test results indicate that the mechanical properties of the silicone rubber specimens changed significantly. We found that both the acid concentration of the test solution and the compression load significantly affected the degradation of the silicone rubber material. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47855.

Screening of sealing materials for PEM fuel cell applications based on weight factor method

“…The high temperature and acidic solution in the PEMFC stack erode the surface of the seal, making the surface of the silicone rubber gasket degrade and even have particles shedding from the gasket, causing safety issues and performance degradation of fuel cells. Previous studies have demonstrated that the stress in rubber samples accelerates the degradation of the material, and the greater the applied stress, the faster the degradation of materials 15,21 . Therefore, a homemade device displayed in Figure 2 was designed for an accelerated degradation experiment 16 .…”

“…Previous studies have demonstrated that the stress in rubber samples accelerates the degradation of the material, and the greater the applied stress, the faster the degradation of materials. 15,21 Therefore, a homemade device displayed in Figure 2 was designed for an accelerated degradation experiment. 16 As demonstrated in Figure 2, the upper and lower plates in contact with the silicone rubber sample are made of PTFE, and the weight is 316 L stainless steel pre-treated with anti-corrosion coating.…”

“…The results revealed that SR and EPDM exhibited the best performance and stability. Afshin et al, 20 Wang et al, 21 Wu et al, 22 and Li et al 23,24 reported the aging and degradation of silicone rubber in acidic solutions under different hydrothermal conditions. The silicone rubber surface gradually erodes with increasing temperature and time, followed by deterioration of its mechanical properties, which may be exaggerated with increasing aging solution concentration.…”

Novel Trends in Proton Exchange Membrane Fuel Cells

“…When this stress is then released, the seal will take some time to restore to its initial shape and may show permanent distortion [175]. This behavior of the seal is known as the 'compression set' and is of great importance in the PEMFC applications [176,177]. Thus, to study the long-term mechanical behavior, compression stress relaxation tests are often conducted to measure the restoring force.…”

Molecular Dynamics Simulation of Oxidative Aging Effect on Diffusion Behaviors of Oxygen and Cyclohexane in NBR

“…Obviously, the gas or liquid molecules have a significant effect on the physical and chemical changes during the oxidative aging process [ 23 , 24 , 25 ]. Meanwhile, the formation of oxygen-containing groups can change the physicochemical properties of the rubber matrix, which may play a positive or negative role in the diffusion mechanism of gases and liquid medium into the rubber matrix, further accelerating or restraining the oxidative reaction rate [ 20 , 26 , 27 ].…”