Chemical aging of the silicone rubber in a simulated and three accelerated proton exchange membrane fuel cell environments

J of Applied Polymer Sci

et al. 2019

Liquid silicone rubber (LSR) products outdoors are often subjected to high intensity of ultraviolet (UV)-A radiation. However, the influence of UV-A radiation on LSR is rarely studied. To study the influence of UV-A radiation on LSR, the surface of LSR with UV-A aging time was characterized by tests at different detection depths [X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDS), and Fourier transform infrared spectroscopy (FTIR)]. The operation properties (thermal stability and mechanical and electrical properties) for outdoor insulators were also analyzed. It was found that the porous surface and the loose layer of LSR increased, but the growth rate of them decreased as UV-A aging time increased. SiO 2 fillers were lost in the surface. C H bonds in CH 3 and CH 3 in Si CH 3 increased with aging time. The increased crosslinking density increased the thermal stability, hardness, dielectric loss tangent, relative dielectric constant, and volume resistivity and decreased elongation-at-break. The mechanical strength initially increased and then decreased. Based on the proposed aging mechanism, the UV-A resistance of LSR can be improved by reducing the amount of hydrogencontaining silicone oil and by increasing the molecular weight of raw rubber.

Section: Resultsmentioning

confidence: 99%

“…Therefore, Si(O) 3 was fitted after UV‐A aging. Si(O) 4 was assigned to SiO 2 fillers and something similar to silica formed in the process of degradation of silicone rubber . Peak fitting was performed for Si, as illustrated in Figure .…”

Section: Resultsmentioning

confidence: 99%

Effect of ultraviolet‐A radiation on surface structure, thermal, and mechanical and electrical properties of liquid silicone rubber

Lin

Yin

J of Applied Polymer Sci

et al. 2019

“…reported that the release of small particles from silicone rubber during the operation of PEM fuel cells ultimately affected their performance. Li et al . reported the chemical degradation of silicone rubber material exposed to several accelerated test solutions for a period of time.…”

Section: Introductionmentioning

confidence: 99%

“…The effect of the temperature on the mechanical properties of silicone rubber was experimentally studied by Rey et al 22 Schulze et al 8 reported that the release of small particles from silicone rubber during the operation of PEM fuel cells ultimately affected their performance. Li et al 23 reported the chemical degradation of silicone rubber material exposed to several accelerated test solutions for a period of time. Liu et al 24 investigated the effect of a silane coupling agent as an additive on the sealing performance of silicone rubber.…”

Section: Introductionmentioning

confidence: 99%

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

Tan

J of Applied Polymer Sci

et al. 2019

Self Cite

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.

“…Silicone is considered to be a potential candidate for PEMFC due to low cost, good mechanical properties and easy manufacturing process [15,16]. There are many reports focusing on the chemical and mechanical stability of silicone rubbers in various testing environments [17,18,19,20,21,22]. Li et al [16,17] investigated the degradation of silicone rubbers exposed to simulated and accelerated proton exchange membrane fuel cell environments.…”

Section: Introductionmentioning

confidence: 99%

Degradation of Silicone Rubbers as Sealing Materials for Proton Exchange Membrane Fuel Cells under Temperature Cycling

Chen

Yan

et al. 2018

Polymers

Gaskets are compressed in proton exchange membrane fuel cells (PEMFCs) to keep fuel, oxidant and coolant within their respective regions and are very important for sealing and maintaining electrochemical performance of fuel cells during their long-term operation. It has been proved that the gas leakage caused by the failure of the gaskets following long-term operation is one of the main reasons for PEMFC performance degradation. In this work, degradation of silicone rubbers, the potential gasket materials for PEMFCs, were investigated in the simulated PEMFC environment solution, weak acid solution, de-ionized water and air, respectively, under alternating temperature cycling from −20 • C to 90 • C. The changes in hardness, weight, chemical properties, mechanical behavior and surface morphology of the samples of silicone rubbers were studied after a certain number of temperature cycles. The results show that with the increase in temperature cycles, the hardness of the samples increases and the weight of the samples decreases gradually. Scanning electron microscopy reveals that cracks and caves constantly appear on the surface of the samples. Attenuated total reflection Fourier transform infrared spectra (ATR-FTIR) results demonstrate that the surface chemistry changes via de-crosslinking and chain scission in the backbone due to the exposure of samples to the environments over time under alternating temperature cycles.