Hydrogen permeation under high pressure conditions and the destruction of exposed polyethylene-property of polymeric materials for high-pressure hydrogen devices (2)-

Aiming to elucidate physical property affecting to hydrogen gas permeability of polymer materials used for liner materials of storage tanks or hoses and sealants under high-pressure environment, as model materials with different free volume fraction, five types of polyethylene were evaluated using two methods. A convenient non-steady state measurement of thermal desorption analysis (TDA), and steady-state high-pressure hydrogen gas permeation test (HPHP) were used both under up to 90 MPa of practical pressure. The limit of TDA method of evaluation for the specimens suffering fracture during decompression process after hydrogen exposure was found. Permeability coefficient decreased with the decrease of diffusion coefficient under higher pressure condition. Specific volume and degree of crystallinity under hydrostatic environment were measured. The results showed that the shrinkage in free volume caused by hydrostatic effects of the applied hydrogen gas pressure decreases diffusion coefficient, resulting in the decrease of permeability coefficient with the pressure rise.     

From the perspective of new technology of blending hydrogen into natural gas pipelines transmission: Mechanism,experimental study,and suggestions for further work of hydrogen embrittlement in high-strength pipeline steels

Blending hydrogen into high-strength pipeline steels for high-pressure transmission may cause materials' hydrogen embrittlement (HE) failure. Although the hydrogen-induced failure of metallic materials has been studied for a long time, the process of hydrogen into the materials, hydrogen-induced delayed failure, and dynamic mechanisms of high-strength pipeline steels under high pressure have not been fully understood. This paper aims to provide a detailed review of the latest research on the hydrogen-induced failure of high-strength pipeline steels in hydrogen-blended natural gas transmission. First, introduced the typical hydrogen blending natural gas pipeline transmission projects and their associated research conclusions. Then, described the physical process of the HE in high-strength pipeline steels and the principle, development, and latest research progress of typical hydrogen embrittlement mechanisms in detail. Third, reviewed the research methods and progress of experimental and theoretical simulations for the HE in steels, including hydrogen permeation (HP) experiments, hydrogen content measurements, hydrogen distribution detection, mechanical property tests, and molecular dynamics simulations. The shortcomings of existing experimental and theoretical simulation methods in the hydrogen-induced analysis of high-strength natural gas pipeline steels under high pressure are discussed. Finally, the future research directions and challenges of this problem are proposed from three aspects: the multimechanism synergy mechanism, the improvement of experimental methods, and the establishment of a new interatomic multiscale model.