Pressure-Dependent Mechanical Behavior and Surface Degradation of Fluorocarbon Elastomer (FKM): Insights into Structure–Property Relationships Under Hydrogen Exposure

This study investigates the pressure-dependent mechanical behavior and surface degradation of fluorocarbon elastomer (FKM, Viton®) O-ring seals following prolonged high-pressure hydrogen exposure. Specimens were aged at up to 7000 psi for 192 h and evaluated using tensile testing and optical image analysis. The results show a non-monotonic evolution of peak force, stiffness, and energy absorption, with increased load-bearing response at higher pressures accompanied by reduced displacement capacity. Normalized force–displacement behavior shows broadly similar loading profiles across pressure conditions; however, this representation is used for comparative visualization and does not establish preservation of the deformation mechanism. Image-based analysis reveals a significant increase in micro-defect density and surface heterogeneity with pressure, suggesting increased formation of surface micro-defects. These findings highlight pressure-dependent changes in polymer network response and surface morphology under hydrogen exposure. The study provides insights into structure–property relationships governing elastomer performance in hydrogen environments.