Wettability after Artificial and Natural Weathering of Polyethylene Terephthalate

The weathering of plastics is always accompanied by a change in surface properties, especially wettability in the case of water. For plastics weathering in an aquatic environment, wettability plays an important role in transport, sedimentation, and dispersion in the water body. To quantify wettability, contact angle measurement is a fast and convenient method that requires little experimental effort. This technique was used with the aim of systematically discussing how measured values of contact angles can contribute to the assessment of the weathering state. Using polyethylene terephthalate (PET), wetting was analyzed on samples from artificial weathering and from controlled, natural weathering. Surface analytical methods were used (Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), ultraviolet and visible light spectroscopy (UV/VIS)) to analyze the parameters affecting the contact angle: (i) chemical bond breaking and formation, (ii) eco-corona formation and biofilm growth, and (iii) change in surface structure and roughness. It was found that wettability with water increased during weathering in all cases. The reasons for this varied and depended on the method of weathering. The improved wettability during artificial weathering was due to changes in the polymer surface chemistry. In natural weathering, however, the formation of eco-corona and biofilm was responsible for the changes.