H-Mat Hydrogen Compatibility of NBR Elastomers

The H2@Scale program of the U.S. Department of Energy (DOE) Hydrogen and Fuel Cell Technologies Office (HFTO) is supporting work on the hydrogen compatibility of polymers to improve the durability and reliability of materials for hydrogen infrastructure. The hydrogen compatibility program (H-Mat) seeks “to address the challenges of hydrogen degradation by elucidating the mechanisms of hydrogen-materials interactions with the goal of providing science-based strategies to design materials, (micro)structures, and morphology with improved resistance to hydrogen degradation.” Previous work on ethylene propylene diene indicated hydrogen interaction with plasticizer increased its migration to the surface and coalescing within the elastomer compound. New research on nitrile butadiene (NBR) has found hydrogen and pressure interactions with a series model rubber-material compounds to behave similarly in some compounds and improved in other compounds that is demonstrated through volume change and compression-set differences in the materials. Further studies were conducted using a helium-ion microscope (HeIM), which revealed significant morphological changes in the plasticizer-incorporating compounds after static exposure and pressure cycling, as evidenced by time-of-flight secondary ion mass spectrometry. Additional studies using x-ray chromatography revealed that more micro-voids/-cracks developed after gas decompression in unfilled materials than in filled materials; transmission electron microscopy (TEM) probed at the nano-meter level showing change in filler distribution and morphology around Zinc-based particles.