EFFECT OF UV IRRADIATION ON THE STRUCTURE OF HETEROPHASIC ETHYLENE-PROPYLENE COPOLYMERS

Changes in [eta] and crystallinity of commercial samples of isotactic polypropylene (i-PP), heterophasic ethylene-propylene copolymers [E-P copolymer] containing < 16 mol% of ethylene and their fractions (havin g ethylene content 40.9 and 55. mol%) upon polychromatic irradiation i n air at 55-degrees-C were studied by comparing unirradiated samples. Crystallinity was evaluated by DSC and X-ray diffraction. Viscosity re sults showed a decrease of molecular weight upon irradiation. DSC and X-ray studies revealed that the transition of alpha-modification to be ta-phase of polypropylene and also that crystallinity of the copolymer decreased initially upon irradiation. However, upon longer irradiatio n, the crystallinity increased again.