Phase field modeling of hydrogen release in nitrile-butadiene rubber composites after high-pressure hydrogen exposure

Experimental data showed that a simple diffusion model doesn't suffice to explain the hydrogen gas (H2) release kinetics in nitrile butadiene rubber (NBR) composites (one with no filler or plasticizer, one with plasticizer only, one with fillers and plasticizer, and one with fillers only) after exposed to hydrogen gas at a pressure of 27.6 MPa. In this work, we developed a phase field model that considers the effect of H2 gas bubble evolution on H2 release kinetics. With the model, we simulated the effect of thermodynamic and kinetics properties on the nucleation, growth, and shrinkage of gas bubbles and H2 release kinetics during and after decompression. The results demonstrated that (1) the model built upon certain thermodynamic and kinetics properties of a given material can well describe its H2 release kinetics measured in experiments, and (2) the model can predict the gas bubble evolution, which is associated with the material property degradation and structural failures, such as cracks and blisters, with accurate thermodynamic and kinetics properties or H2 release data from experiments.