Molecular Dynamics Study of Hydrogen Dissolution and Diffusion in Different Nonmetallic Pipe Materials

Abstract

The nonmetallic pipes can effectively avoid the hydrogen embrittlement of metal pipes when transporting hydrogen. However, due to the characters of the nonmetal materials, there will be a large degree of gas permeation when conveying hydrogen by nonmetallic pipes. To select suitable nonmetal pipe materials, the solubility, diffusivity, and permeability of hydrogen in PE, PVC and PVDF amorphous polymers are investigated and compared by molecular dynamics simulations at 270–310 K and 0.1–0.7 MPa, providing guidance for the construction of nonmetallic hydrogen transportation pipes. Simulation results indicate that the solubility coefficients of hydrogen in PE and PVDF rise with the increasing temperature, but show an opposite trend in PVC. Both the diffusion and permeability coefficients increase with the rise of temperature. In a small range of pressure variation, the influence of pressure on diffusion and permeation characteristics is ignorable. Among the three studied amorphous polymers, the permeability coefficient of hydrogen in PE is the largest and that in PVDF is the smallest. In addition, the diffusion of hydrogen molecules in the polymer conforms to the hopping mechanism.