In Situ Positron Lifetime Measurement for the strained polyethylene

摘要

The in situ positron annihilation spectroscopy measurement has been developed and applied to investigate the structural change in free volume on the tensile deformation of linear low-density polyethylene. The pick-off lifetime of ortho-positronium (Ps) decreases by applying the strain and an aging variation cannot be observed. On the contrary the fraction of Ps formation gradually decreases day by day and becomes constant after several days. Further, after release of strain, it returns to the original value. The reason is considered to be that the molecular chains become rigid gradually during deformation and they lose the flexibility.