Quantitative Structure Activity Relationship Analysis of Polypropylene during Ultraviolet Aging Based on Tensile Strength

Abstract

In order to improving ultraviolet radiation (UV) aging resistance of polypropylene (PP) and expanding its application range, it is necessary to research the rule and mechanism of PP in UV aging process. On the base of Fourier transform infrared spectroscopy and differential scanning calorimetry characterization, the variations of structure parameter (crystallinity and carbonyl index) of homo-PP corresponding to different UV aging time were calculated and analyzed. Combined with tensile strength testing, the influences of both crystallinity and carbonyl index on tensile strength in UV aging process of PP were researched. Then the relationship formula between tensile strength and structure parameter was constructed based on linear relationship, and the quantitative structure-activity relationship of PP during UV aging was analyzed. The results show that, with the extending of aging time, the influence of crystallinity on tensile strength of PP declines, while that of carbonyl index is on the contrary. During UV aging, the tensile strength of PP rises slightly with the increase of crystallinity first, then acceleratedly declines for the increase of carbonyl index. It should be noted that, although the crystallinity of PP begins to decline after 100 h UV aging, its effect to tensile strength can’t be ignored while aging time is less than about 300 h.