Outdoor and accelerated laboratory weathering of polypropylene: A comparison and correlation study

The degradation behaviors under outdoor and accelerated laboratory weathering conditions of isotactic polypropylene (iPP) were compared, aiming to establish a correlation between both weathering types. Outdoor weathering experiments were performed at six national standard natural exposure stations which represent six typical climate types in China. The evolutions in the chemical/molecular structure, surface morphologies, mechanical and crystalline properties were compared and the results suggested that the accelerated weathering experiment is substantially capable to mimic the main outdoor weathering behaviors. The degradation mechanism for all weathering conditions is consistent according to the similarity in the species and proportions of the carbonyl products. An improved Arrhenius equation, which considered the multiple effects of temperature, irradiation and oxygen pressure, was proposed to correlate the outdoor weathering behavior of iPP with that of accelerated laboratory weathering. The predictions for the outdoor weathering behavior of iPP based on this approach were satisfactory compared with the experimental results. Depending on the outdoor exposure locations, the acceleration of laboratory weathering was found to range from 8 to 30 times in comparison to outdoor weathering.