Lab test finds modified graphite lowers hydrogen permeation but not blistering

An experimental sealing composite made from thermoplastic polyurethane, ethylene propylene diene monomer, modified graphite and EPDM-g-MAH showed improved hydrogen-barrier performance under laboratory conditions, but visible blistering remained after rapid decompression. The optimized formulation, designated G5, combined TPU, EPDM, modified graphite and EPDM-g-MAH at a mass ratio of 90/10/5/2. Researchers evaluated its hydrogen permeation at temperatures of 25–85 °C and pressures of 1–3 MPa, measured differential-pressure permeation at 10 MPa, and assessed hydrogen uptake and volume change following exposure at 20 MPa and rapid decompression.

The study found that the hydrogen permeability of G5 increased as temperature rose and, within the tested 1–3 MPa range, as pressure increased. At 25 °C and 10 MPa, its permeability coefficient was 0.794 × 10−9 mol·m/(m²·s·MPa), lower than that measured for neat TPU. The comparison supports an improvement in hydrogen-barrier performance for the tested composite formulation. The experiment concerned a laboratory composite rather than a complete industrial sealing component, and the reported results apply to the temperatures, pressures and formulations examined.

After exposure to hydrogen at 20 MPa followed by rapid decompression, G5 showed lower measured post-exposure hydrogen uptake and less swelling than the other tested composites. These two measurements indicated that the optimized material retained less hydrogen and underwent a smaller relative volume change under that test procedure. The improvement was not sufficient to prevent visible blistering following rapid decompression. The findings therefore distinguish reduced permeation, hydrogen uptake and swelling from the material’s continuing susceptibility to visible damage under the reported decompression conditions.

Temperature and pressure were tested as variables in the permeation experiments, while the high-pressure exposure and decompression procedure provided a direct assessment of retained hydrogen, relative volume change and visible surface damage. Across those measurements, the evidence shows that the G5 formulation performed better than neat TPU on hydrogen permeability and better than the other tested composites on post-exposure uptake and swelling. At the same time, the surviving blisters show that lowering permeability did not completely suppress rapid-decompression damage. The study is an experimental evaluation of a specific TPU/EPDM/modified-graphite material system at the stated test conditions, rather than a general demonstration of composite performance under every operating environment.

Subject of Research: Laboratory evaluation of hydrogen permeation and rapid-decompression damage in a TPU/EPDM/modified-graphite sealing composite.

Article Title: High-pressure hydrogen permeation and rapid-decompression behavior of TPU/EPDM/modified-graphite sealing composites

Article References: Mou, W., Li, X., He, G., You, J., & Zhou, C. (2026). High-pressure hydrogen permeation and rapid-decompression behavior of TPU/EPDM/modified-graphite sealing composites. Journal of Materials Science. https://doi.org/10.1007/s10853-026-13893-4

Image Credits: AI Generated

DOI: 10.1007/s10853-026-13893-4

Keywords: hydrogen permeation, TPU composite, EPDM, modified graphite, rapid decompression, hydrogen sealing, polymer swelling, hydrogen uptake, blistering, materials testing, High-pressure, hydrogen