Crack Growth Behavior of Sealing Rubber under Static Strain in High-Pressure Hydrogen Gas

Abstract

In order to enable hydrogen society in the near future, it is necessary to clarify the influence of hydrogen on the mechanical, physical and chemical properties of the materials used for hydrogen energy systems. In the case of rubbers, there is a particular danger of mechanical damage resulting from internal fracture, which occurs when high-pressure hydrogen gas is suddenly decompressed. Although our previous studies focused on fracture and deformation caused by high-pressure hydrogen decompression, the fracture and deformation of rubber materials under pressurization have not been studied. From this viewpoint, static crack growth tests of an unfilled sulfur-crosslinked ethylene-propylene-diene monomer (EPDM) rubber were conducted in hydrogen gas at 10 MPa and room temperature (around 25°C) by using a high-pressure hydrogen vessel with glass viewing ports. Deformation of the rubber during pressurization was hardly seen at ≤ 10 MPa, although hydrostatic pressure was applied and hydrogen gas penetrated into the rubber. The static crack growth rate for hydrogen gas at 10 MPa was consistent with that in air (0.1 MPa). A lot of facets with about 100 µm in size caused by the initiation and successive coalescence of secondary cracks ahead of the main crack were observed on the fracture surface of the specimens tested in air and hydrogen gas at 10 MPa, and these fracture surfaces showed a similar aspect. From these results, it was clarified that a hydrogen environment at ≤ 10 MPa did not influence the static crack growth characteristic of the rubber.