CHAIN-SCISSION AND BLEACHING IN HETEROPHASIC ETHYLENE-PROPYLENE COPOLYMERS

The variations in the viscosity and gloss (yellowness and whiteness in dex) in isotactic polypropylene, heterophasic E-P copolymers and polye thylene were measured during photo-oxidation. The samples underwent ex tensive reduction in intrinsic viscosity [eta] upon U.V. irradiation. The kinetics of oxidative degradation have also been studied using pol ychromatic light at 60 degrees C in air. These parameters appear to be a sensitive criteria to characterize the photo-oxidative transformati on of polymers. The course of degradation is random and the yellowing process brought by the short wavelength U.V. light is accompanied by a photobleaching reaction which is caused by the light of longer wavele ngths.