Natural weathering severity of typical coastal environment on polystyrene: Experiment and modeling

Natural weathering of polystyrene (PS) was performed at six exposure sites with various climate types along the coastal line from China to Europe, including Qionghai (typical hot-humid climate), Sansha (island hot-humid climate), Chennai (savanna hot-humid climate), Jeddah (xerothermic climate), Sanary-sur-Mer (mediterranean climate), Hoek van Holland (warm-temperate climate). The chemical structure, morphology and color changes of PS after weathering were characterized by FTIR, DSC, SEM and Color spectrometer, and relative weathering severity of different climates on PS were compared. Results show that Sansha has the highest severity value while the severity value of Hoek van Holland is the lowest. The degradation degree of PS at the sites of Qionghai, Sansha, and Chennai is higher than that at other sites, resulted in a deterioration of the optical properties and serious damage of the sample surface. In the xerothermic climate, the optical properties of PS decrease drastically during the process of natural weathering, while only slight change in hydroxyl index and carbonyl index is observed, and micrographic surface does not differ from the surface of un-weathered materials. For other climates, the degradation degree was low, resulting in a relative slow change of optical properties and long time for the appearance of surface defects. In order to quantify the relative severity of these climates, a mathematic model was proposed based on the basic degradation principle of polymer materials, which could predict the failure time of PS. The failure time was predicted by the model using gloss loss of PS as failure index, with an accuracy up to 99.2%.