Chain photoradical reactions in polyethylene

Abstract

The kinetics and mechanism of the photochemical reactions of macroradicals and accumulation of gaseous products under UV illumination of γ-irradiated polyethylene have been studied. The photochemical reactions of macroradicals result in the formation of an active free radical (H, ĊH 3). The latter reacts with polyethylene forming initial macroradicals and so on. These chain photoradical reactions are responsible for the formation of hydrogen, methane, ethylene, transvinylene double bonds and cross-links and for scission. The chain length of the reactions is ∼40. The products of the reaction have been distributed nonhomogeneously. The excited alkyl radicals transfer their energy to the repulsive triplet state of the macromolecule CH bond, resulting in bond break-up. Moreover, the alkyl radical can dissociate under UV illumination.