The study of the crystallinity effect on the structural change of nylon 11 exposed to high-pressure hydrogen gas

This study was specifically focused on how different degrees of crystallinity affect the structural changes in crystalline polymers when exposed to high-pressure hydrogen gas. Four nylon 11 samples with different crystallinities were prepared and subsequently exposed to 90 MPa hydrogen gas for one day, followed by rapid decompression. The differences in structure before and immediately after exposure, as well as the structural recovery process over approximately several days, were investigated mainly by wide-angle X-ray diffraction (WAXD) and smallangle X-ray scattering (SAXS). For all nylon 11 samples, the WAXD results indicated increased crystallinity due to exposure, while the SAXS results indicated void formation during the depressurization process. The SAXS results also indicated that the voids gradually shrank with time after decompression and that the time dependence of shrinkage was strongly correlated with crystallinity.