Effect of Low Gamma-Irradiated dose on the Structure of Cellulose Triacetate Films: II. Positron Annihilation Spectroscopy

Positron annihilation spectroscopy, thermogravimetric and FT-IR techniques are used to study the effect of low doses of gamma irradiation on microscopic structure of cellulose triacetate films. The irradiation is done at room temperature with doses ranging from 5 to 25 kGy. The ortho-positronium lifetime component associated with the pick-off annihilation of positronium trapped by the free volume is analyzed. Alternation in the ortho-positronium lifetime is observed reaching to a minimum value at10 kGy which is followed by a sharp increase at 15 kGy. Afterward, the ortho-positronium lifetime remains almost constant up to 25 kGy. The intensity of ortho-positronium component, I3, revealed an opposite trend with respect to the ortho-positronium lifetime manner. The obtained results are discussed on the basis of free volume model. The thermogravimetric and FT-IR measurements bearded out the findings of positron annihilation spectroscopy and explained the variations on the CTA microstructure due to the effect of the low doses of gamma irradiation.