Impedance spectroscopy for in situ and real-time observations of the effects of hydrogen on nitrile butadiene rubber polymer under high pressure

Nondestructive impedance spectroscopy (IS) was developed and demonstrated to detect the effects of hydrogen on nitrile butadiene rubber exposed to hydrogen gas (H(2)) at high pressures up to 10 MPa. IS was applied to obtain an in situ and real-time quantification of H(2) penetration into and its desorption out of rubber under high pressure. The diffusion coefficients of H(2) were also obtained from the time evolution of the capacitance, which were compared with those obtained by thermal desorption gas analysis. The in situ measurements of the capacitance and the dissipation factor under various pressures during cyclic stepwise pressurization and decompression demonstrated the diffusion behaviour of H(2), the phase of the rubber under high pressure, the transport properties of H(2) gas, and the physicochemical interaction between H(2) and the rubber. These phenomena were supported by a COMSOL simulation based on the electric current conservation equation and scanning electron microscopy (SEM) observations.