RADICAL YIELDS IN IRRADIATED POLY(ETHYLENE-TEREPHTHALATE) FIBERS

The formation of free radicals and their subsequent decay in irradiated polyethylene terephthalate monofilaments was studied by e.s.r. under a variety of conditions. A yield of 0.023 radicals per 100 eV was found, in agreement with the literature values. Reduced values were found in the presence of water, methylene chloride and chlorine. The decay followed a two-stage second order pattern presumably due to radicals in the crystalline and amorphous regions. At -196°C, G values of 0.7 of trapped electrons were found, rapidly decaying as the temperature was raised. At about -135°C the signal changed to the characteristic signal found at room temperature with a G value of 0.42. On adding methylene chloride to irradiated PET, comparatively rapid decay of the trapped radicals took place, the rate corresponding closely to the rate of sorption of the methylene chloride into the monofilaments. This indicated very rapid decay even from the crystalline regions, once the solvent is present. A number of other observations are presented and interpreted in relation to, for example, the radiation grafting yields in the presence of solvents. © 1979.