Molecular dynamics insights into the influence of carbon black on hydrogen permeation in rubber seals for hydrogen infrastructure

Abstract

Understanding the microscopic mechanisms by which fillers influence hydrogen permeation behavior in rubber is crucial for optimizing rubber sealing materials for high-pressure hydrogen environments. In this study, molecular dynamics (MD) simulations were used to construct the ethylene propylene diene monomer (EPDM) and nitrile butadiene rubber (NBR) composite models filled with different carbon black (CB) contents, aiming to investigate the hydrogen permeation behavior of the rubber composites under different pressure conditions. The results reveal that NBR exhibits lower hydrogen diffusion, solubility, and permeability than EPDM under identical conditions. The diffusion of EPDM-CB and NBR-CB decreases with increasing pressure. An increase in CB content leads to a reduction in the free volume distribution of both EPDM and NBR, consequently decreasing the hydrogen diffusion. However, CB provides additional hydrogen adsorption sites, which increases hydrogen solubility as the filler content rises. The simulation results exhibit a trend consistent with experimental data, and the effect of CB on hydrogen permeability shows a pattern similar to that of diffusion. In this study, the transport mechanisms of hydrogen in rubber composites were explained at the molecular level, offering valuable guidance for the design and development of rubber sealing materials with enhanced hydrogen compatibility. Highlights: A simulation model for hydrogen permeation in CB-rubber is established. The effect of high pressure on the hydrogen diffusion in rubber is elaborated. The effect of CB on the hydrogen barrier properties of rubber is analyzed. Micro-mechanism of hydrogen permeation within rubber is elucidated.