Physical and mechanical behaviour of NBR and EPDM rubbers under high pressure hydrogen conditions

Polymeric components in hydrogen infrastructure face a significant challenge: the risk of damage from rapid gas decompression (RGD), which can ultimately compromise operational safety. This study investigates the impact of high-pressure hydrogen exposure on various rubber formulations: carbon black (CB) and silica (Sil) filled acrylonitrile butadiene rubber (NBR), as well as CB-filled ethylene-propylene-diene monomer rubber (EPDM). The materials were subjected to both static and dynamic high-pressure hydrogen environments. Their physical, mechanical, and chemical properties immediately after decompression and 48 h later were analysed. Our findings reveal a trend of the material to undergo tensile stiffening up to 24% after cyclic hydrogen exposure. The mechanism behind the increased stiffness is associated with a combination of microstructural mechanisms, polymer-filler interfacial rearrangement, and possible additive migration, depending on the grade. Silica-filled NBR demonstrates a faster volume recovery among all grades, but lower mechanical stability compared to its CB-filled counterparts, while the presence of plasticisers appears to accelerate crack formation under both static and dynamic loading conditions. The non-plasticised CB-filled NBR grade showed the best overall balance amongst the tested materials, particularly in tensile property retention, structural integrity, and resistance to crack formation under the applied exposure conditions. These findings contribute to the development of safer and more resilient materials for operational performance in hydrogen applications.