Evaluation of Hydrogen Permeation Characteristics in Rubbery Polymers

To find suitable sealing material with low permeability against hydrogen, the elaborated evaluation techniques for hydrogen transport properties are necessary. We developed two techniques determining the permeability of hydrogen including software for diffusion behavior analysis. The techniques contain gas chromatography and volumetric collection of hydrogen gas. By measuring the hydrogen released from polymer samples with respect to the elapsed time after being decompressed from the high pressure, total amount of adsorption and diffusivity (D) of hydrogen are evaluated with self-developed program of Fick's diffusion equation specified to a sample shape. The solubility (S) and permeability (P) of the polymers are determined through Henry's law and a relation of, P=SD respectively. Developed techniques were applied to three kinds of spherical-shaped sealing rubbers, NBR, EPDM, and FKM. The D, S and P have been measured as function of pressure. The permeability obtained by both methods are discussed with Comsol simulation.