Study on Crystal Structure Transformation and Aging Resistance of Polypropylene Induced by UV Light

The effects of UV irradiation on the morphology and surface structure of α-nucleated PP(α-PP),β-nucleated PP(β-PP),and neat PP were studied.Lower degradability was found in β-PP as compared with α-PP and neat PP.The gross degree of crystallinity of all samples showed an initial increase in short-time exposure followed by decrease with prolonged exposure.The maximum degree of crystallinity for β-PP was 65.5 % at 312 h and for α-PP was 74.6 % at 456 h.The β-phase in β-PP reached a maximum of 30.9 % at 144 h exposure,followed by a decrease with prolonged exposure.The α-phase in β-PP increased after short-time and then decreased,leveling off to 48 % after 312 h exposure.