Thermo‐Alkaline Coupled Aging of Modified Polytetrafluoroethylene Gaskets in Alkaline Water Electrolysis: Failure Behavior Analysis

ABSTRACT Sealing gaskets are critical to alkaline water electrolysis (AWE) systems, yet their thermo‐alkaline degradation remains insufficiently quantified. Modified polytetrafluoroethylene (m‐PTFE) composite gaskets were aged in 30 wt% KOH for 168 h at 20°C, 60°C, 90°C, 120°C, and 150°C. For this commercial composite, 90°C was the first tested temperature showing a marked decrease in displacement‐based elongation at break, from 157.61% ± 7.08% to 108.87% ± 3.88%. Tensile strength decreased numerically at 20°C, while recovery ratio and tensile strength increased numerically at 150°C relative to 120°C; these pairwise differences were not statistically significant after Holm adjustment. Differential scanning calorimetry located pristine‐composite melting above the aging range, while Fourier transform infrared spectroscopy showed retention of dominant PTFE bands. Thermogravimetric analysis revealed lower temperatures for 5% mass loss after aging. External‐surface scanning electron microscopy–energy dispersive X‐ray spectroscopy revealed cavities, surface heterogeneity, and increased constituent exposure. Morphological evolution and possible changes in interfacial interactions and load sharing offer a potential explanation for the observed mechanical response. These findings describe the response of the tested material at the selected temperatures and under the specified exposure protocol, providing reference data on material properties relevant to sealing applications.