Controlled Aging and Degradation of Selected Plastics in Marine Environment: 12 Months of Follow-up

This study aims to determine the properties of common polymer items after their exposition to aging conditions in marine environment. Natural weathering tests were conducted on aging boxes, cups, films and bottles in the beach shoreline, on the sea surface, and underwater in Villasimius (CA), Italy. The samples were harvested after 3, 6, 9, and 12 months. The three environments are characterized by different extents of solar radiation, heat, humidity, and biological interactions. Tensile tests are performed to evaluate the progressive decay of mechanical properties as a function of aging periods. Differential Scanning Calorimetry was employed to monitor the variation of oxidation onset temperature (OOT), related to the thermal stability of the material. Infrared (FTIR) spectroscopy was carried out to assess the extent of the oxidation phenomena, associated to the formation of a carbonyl peak. Various rheological tests were used to assess the molecular weight of the polymer samples. Capillary viscometry was utilized for polylactic acid and polystyrene, whereas polyolefins were studied with rotational melt viscometry. Colorimetry tests were performed to evaluate the yellowing of the items, attributable to the oxidation of macromolecules. Ssamples aged underwater showed the smallest degradation effects for vinyl polymers (PE, PP, PS), whereas polyesters, such as PET and PLA, showed higher sensitivity to the weathering due to hydrolysis phenomena. The most detrimental factor for vinyl polymer degradation appears to be the (UV) light in the beach shoreline.