A effect of moisture on photo-degradation for polypropylene

Photo-degradation of polymers for outdoor use are accelerated by degradation factors such as heat and moisture. Polypropylene(PP) is excellent in water resistance, but is inferior to weatherability. Therefore, in this study, PP was exposed under the water spray condition by using Xenon arc lamp. We evaluated the synergistic effect of light and moisture using the quantification technique of degradation. Results from the Fourier-transform infrared spectroscopic and X-ray Photoelectron Spectroscopy revealed that moisture accelerated the oxidative degradation of PP. In addition, with the progress of the oxidative degradation, melting point and thermal decomposition temperature of PP was lowered. The resulting collapse of crystal structure and chain scission therefore deteriorated the mechanical properties (Charpy impact strength, elongation) of PP.