Abstract: 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 on short-time exposure followed by decrease with prolonged exposure. The maximum degree of crystallinity for β-PP was 65.5% at 312h and for α-PP was 74.6% at 456h. The β-phase in β-PP reached a maximum of 30.9% at 144h 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 312h exposure.

Key words: polypropylene, α-crystal, β-crystal, photo degradation, crystal transformation