Swelling measurement during sorption and decompression in a NBR exposed to high-pressure hydrogen

Unlike for other gases, the volume change of the rubber materials due to the sorption of hydrogen is very low and hence difficult to measure. Conversely, the volume change occurring during decompression is significantly more than that occurring during sorption equilibrium. The aim of the present experiment is to measure the significantly different volume changes due to hydrogen content during the two stages of a high-pressure exposure cycle at room temperature simultaneously. Spherical samples of unfilled NBR were tracked by two high and low-resolution devices, with a good connection of measurements series in both conditions. The effect of thermal expansion (Joule-Thomson effect) and the compressibility contributions were removed to measure the term due to hydrogen sorption precisely.