Hydrogen permeation behavior of common polymers in pure hydrogen environment

Objective Pipeline hydrogen transportation is the most cost-effective solution for long-term, large-scale and long-distance hydrogen transport. However, pipeline steel is susceptible to hydrogen embrittlement in such environments. Replacing pipeline steel with non-metallic polymers can mitigate this issue. Currently, research on hydrogen permeation in polymers is limited, highlighting the need for a more systematic and intuitive study.

Methods Six typical polymers used in pipeline systems—polyethylene (PE), polyamide (PA), polypropylene (PP), polyether ether ketone (PEEK), polyvinylidene fluoride (PVDF), and nitrile butadiene rubber (NBR)—were selected for study. Their microscopic morphology, chemical composition, and crystal structure were characterized after hydrogen permeation at low pressure (0.5 MPa) and various temperatures. Hydrogen permeation coefficients at different temperatures were calculated, and permeation behavior was analyzed based on the characterization results and coefficients.

Results For PE, PA and PP—potential hydrogen pipe materials—no significant pores or cracks were observed on the cross-section at room temperature. At elevated temperatures (around 50 °C), PE exhibited less severe pores and cracks than PA and PP. All three materials showed a slight decrease in crystallinity, with no notable changes in chemical composition or crystal structure. For PEEK, PVDF and NBR—potential sealing materials—no obvious delamination or damage was detected at room temperature. At elevated temperatures (～50 °C), PEEK exhibited slight roughening, while PVDF and NBR exhibited relatively dense pore formation with a risk of through-cracks. The chemical composition and crystal structure of all three sealing materials remain largely unchanged, with no decrease in crystallinity. Overall, PE and PEEK demonstrated the greatest resistance to hydrogen permeation, with minimal changes in microscopic morphology, chemical composition, and crystal structure.

Conclusion The research findings can inform the selection of non-metallic pipe and sealing materials in the preliminary design of urban pure hydrogen pipeline networks. It is recommended to prioritize PE and PEEK in choosing non-metallic materials for future urban low-pressure pure hydrogen or hydrogen-blended pipelines.