Poster: Hydrogen Diffusion In Oversaturated EPDM Rubber: The Effect Of Induced Strain

The development of hydrogen based energy and associated storage and distribution has lead to an infrastructure dependent on an advanced understanding of hydrogen materials interactions. To contain the high pressures associated with compressed hydrogen gas, multi-material components are crucial, of which polymers are used for parts such as O-rings, pipes, hoses, and inner liners of high pressure tanks. Although polymers are chemically inert when exposed to hydrogen gas, the cyclic pressurization and depressurization of hydrogen through polymer materials prompts mechanical failures. Previous experimental and computational works have explored the rapid decompression failure of rubbers leading to an understanding of polymer deformation as a function of hydrogen diffusion. However, we hypothesize that the diffusivity of hydrogen in rubber is influenced by local strain of the elastomeric material requiring an atomistic scale inquiry and description. In this work we establish a method to study hydrogen diffusion in strained ethylene-propylene-diene monomer (EPDM) rubber using molecular dynamics simulations of cross-linked and uncross-linked EPDM models at three pressurization levels (20, 40, 80 MPa) relevant to the hydrogen infrastructure. We report the diffusion coefficients of hydrogen gas as a function of nominal strain and describe the hydrogen accessible free volume in strained configurations that determine the magnitude and behavior of hydrogen mobility. This work is valuable as input to higher length scale diffusion-deformation models that are dependent on values of principle strain to predict damage as well as experimental efforts that seek to identify changes in structural features due to hydrogen exposure.

Sandia National Laboratories is a multi-mission laboratory managed and operated by the National Technology and Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA-0003525.