First attempt at in situ Fourier transform infrared absorption spectroscopic study on polymer materials under a high-pressure hydrogen gas environment

Abstract Hydrogen is poised to become a primary energy medium in the future. Polymer products are indispensable as sealing materials in hydrogen-energy facilities. To obtain concrete information about the effects of high-pressure hydrogen exposure on polymer materials, an attempt was made to follow structural changes induced by high-pressure hydrogen exposure using Fourier transform infrared spectroscopy. To this end, a sample cell equipped with 2 diamond windows, which facilitates in situ measurements up to 100 MPa, was developed. The structural changes in 2 kinds of polyethylene, high- and low-density polyethylene, with varying hydrogen pressure (0 to 90 MPa) were traced to validate the experimental system. Using this system, spectral changes corresponding to the variation in the lateral packing of polyethylene chains, degree of crystallinity (DC), and voids were observed. The findings indicate that DC exerts a substantial influence on the structural alterations induced by high-pressure hydrogen, thereby validating the efficacy of this methodology.