Chain-scission and bleaching in heterophasic ethylene-propylene copolymers

The variations in the viscosity and gloss (yellowness and whiteness index) in isotactic polypropylene, heterophasic E-P copolymers and polyethylene were measured during photo-oxidation. The samples underwent extensive reduction in intrinsic viscosity [[UNKNOWN]] upon U.V. irradiation. The kinetics of oxidative degradation have also been studied using polychromatic light at 60°C in air. These parameters appear to be a sensitive criteria to characterize the photo-oxidative transformation 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 wavelengths