Volumetric analysis technique for analyzing the transport properties of hydrogen gas in cylindrical-shaped rubbery polymers

We report volumetric analysis techniques to analyze the transport properties of hydrogen dissolved in cylindrical-shaped polymers. The techniques utilize the volume measurement of the released hydrogen from rubber by gas collection in a graduated cylinder after charging sample with high-pressure hydrogen and subsequent decompression. We further improve the graduated cylinder with some modifications, such as reading the electrical capacitance of the water level using electrodes and changing the sample loading position. From the measurement results, the uptake (C∞), diffusion coefficient (D), and solubility (S) of hydrogen are quantified with an upgraded diffusion analysis program. These methods are applied to three cylindrical rubbers. Dual adsorption behaviors with increasing pressure are observed for all the samples. C∞ follows Henry's law up to ~15 MPa, whereas Langmuir model applies up to 90 MPa. D shows Knudsen and bulk diffusion behavior below and above pressure, respectively. A COMSOL simulation is compared with experimental observations.