Pressure-dependent mechanical behavior and surface degradation of EPDM and NBR elastomer seals after prolonged high-pressure hydrogen exposure

Elastomeric seals are critical for hydrogen infrastructure, where mechanical integrity governs reliability and leakage prevention. This study investigates the pressure-dependent mechanical behavior of EPDM and NBR O-ring seals after prolonged high-pressure hydrogen exposure. Specimens were exposed to hydrogen up to 7000 psi (≈48 MPa) for 192 h and evaluated using displacement-controlled tensile testing, short-time stress relaxation, and surface characterization. Results show a non-monotonic evolution of peak force with increasing hydrogen pressure, indicating competing effects of hydrogen sorption, internal stress development, and viscoelastic relaxation. Both materials exhibit increased variability and faster relaxation after exposure, with NBR showing more pronounced changes. Surface analysis reveals greater degradation in NBR compared to EPDM. These findings highlight that hydrogen exposure alters mechanical stability of elastomer seals and emphasize the need for pressure-dependent and time-dependent evaluation in hydrogen applications.