GAMMA-INITIATED, PHOTO-INITIATED, AND THERMALLY-INITIATED OXIDATION OF LINEAR LOW-DENSITY POLYETHYLENE - A QUANTITATIVE COMPARISON OF OXIDATION-PRODUCTS

The detailed oxidation products from the initiated oxidation of linear low density polyethylene have been compared by the use of infrared spectroscopy combined with chemical derivatization. Oxidized films were treated with NO or SF4 to allow the resolution of the various alcohol and hydroperoxides and of the carbonyl species, respectively. All types of initiation gave very similar products but in varying quantities. In photooxidation, hydroperoxide was clearly shown to approach a photostationary concentration either from below for fresh film or from above for samples that had been pre-oxidized by gamma-irradiation, prior to UV exposure. Carboxylic acid groups, the main backbone scission product, dominated in photooxidations, possibly as the result of the further oxidation of sec-hydroperoxide sites.