High-pressure hydrogen permeability model for crystalline polymers

Molded seal devices made of crystalline polymers are widely used in high-pressure hydrogen equipment. A method for evaluating high-pressure hydrogen permeability was recently reported; however, the evaluation cost is extremely high. To select suitable crystalline polymers for molded hydrogen seals or barrier devices, a high-pressure hydrogen permeability prediction method using the polymer structure and its conventional properties is required. In this study, we measured the pressure dependency of the hydrogen permeability of low-density polyethylene (LDPE), high-density polyethylene (HDPE), and polyamide 11 (PA11). We constructed the permeation model for crystalline polymers in terms of the tortuosity induced by their higher-order structures and free volume change in the amorphous region evaluated using PVT method for measuring the relationship between pressure (p), specific volume (v) and temperature (T) in the molten-solid state of a polymer. The results of the pressure dependency of hydrogen permeability were reproduced by the developed permeation model.