||Structural Evolution in Deformed Polyethylene Studied with Positrons
Yamawaki, M. ,
Oka, T. ,
Sato, K. ,
Uesugi, N. ,
Hattori, K. ,
Nagasawa, N.Washio, M.
Different kinds of polyethylene were subjected to uniaxial deformation and their structural evolution was investigated by positron annihilation lifetime spectroscopy (PALS) and coincident Doppler broadening spectroscopy (CDB). The pick-off annihilation lifetime of ortho-positronium (o-Ps) was progressively shortened by deformation, possibly due to anisotropic elongation of the free volume and enhanced overlap of the o-Ps wavefunction with the surrounding polyethylene molecules. The anisotropy elongation of the free volume in deformed polyethylene was also implied by CDB. The intensity of o-Ps was enhanced in high density polyethylene (HDPE) and ultra-high-molecular-weight polyethylene (UHMWPE) by deformation, but not in low density polyethylene (LDPE). This suggests that the destruction of crystallites may play a significant role in the deformation of HDPE and UHMWPE but not in LDPE. Comparison of the PALS data, obtained with two specimens sandwiching the positron source, with those obtained with a single specimen by using a commercial PALS system recently developed by Yamawaki et al confirmed the usefulness of the commercial PALS system in the study of deformed polymers.
18th International Conference on Positron Annihilation(ICPA2018)