Understanding hydrogen-polymer interactions is essential for designing lightweight and durable hydrogen storage systems for future, sustainable mobility. This study applies molecular dynamics simulations to examine hydrogen solubility, diffusion, permeation and the resulting mechanical response in two representative thermoplastic polymers: polyethylene (PE) and polyamide 6 (PA6). Hydrogen uptake was determined through Grand Canonical Monte Carlo methods, while diffusion coefficients were derived from a mean-squared-displacement analysis. Permeability coefficients were obtained as the product of solubility and diffusivity according to the literature. To assess the mechanical behavior, uniaxial tensile tests were simulated on an atomic scale, under various pressures with and without dissolved hydrogen. The results show that the amorphous regions of PE exhibit a permeability coefficient approximately one order of magnitude higher than that of the amorphous regions of PA6. The semi-crystalline nature of polymers was considered by applying an analytical correction. The corrected permeability values align well with the experimentally measured data from the literature with deviations between -34 % and +24 % for PE and PA6, respectively. In a hydrogen-saturated state, both polymers reveal a marked hydrogen-induced reduction in mechanical response, with PE losing up to 75 % and PA6 up to 85 % of their predicted stiffness under elevated hydrogen pressures and tensile loading conditions. The findings provide molecular-level insights into hydrogen-induced mechanisms in polymers which show high potential to be used in thermoplastic composites for the next generation of Type V hydrogen vessels.
Huber et al. (Mon,) studied this question.