EFFECT OF THE PHENOLIC ANTIOXIDANTS ON THE STRUCTURE OF GAMMA-IRRADIATED MODEL POLYETHYLENE

High energy radiation has been successfully employed to modify the che mical structure of commercial polymers. It induces at least two types of reaction in polyethylene: crosslinking and chain scission. In addit ion the efficiency of the radio-induced reactions can be affected by t he presence of antioxidants. The purpose of this work is to study the effect of the irradiation on a model polyethylene containing a phenoli c type antioxidant. Samples containing 0.1% and 1% by weight of Irgano x 1010 (Ciba-Geigy) were irradiated under vacuum at room temperature w ith different doses of gamma rays from a Co-60 source. Changes in stru cture and the average molecular weight were followed by gel permeation chromatography and low angle laser light scattering. The critical dos es for gelation were determined as a function of the antioxidant conce ntration. Theoretical calculations to predict the evolution of molecul ar structure with extent of radiation were performed using a probabili ty model. The agreement between the calculated and the measured molecu lar weights is very good.