Gamma irradiation effects on UV-cured polymers based on acrylate oligomers studied by positron annihilation lifetime spectroscopy

Positron annihilation lifetime spectroscopy is applied to the study of gamma irradiation effect on polymers based on the acrylate oligomers. The measurements have been made on samples with different absorbed dose in the range 10-100 kGy. The longest lifetime, τ3, in three-component analyses of the spectra was associated with the pick-off annihilation of ortho-positronium trapped in free volumes. After irradiation changes in the o-Ps lifetimes and the relative intensity of the longest component, I3, was observed. These results are discussed on the basis of a free volume model.