Monitoring polymer degradation under different conditions in the marine environment

Abstract

The perdurability of plastics in the environment is one of the major concerns of plastic pollution and, as a consequence, oceans are accumulating large amounts of plastic. The degradation of conventional and biobased materials was evaluated through a laboratory experiment for a year simulating four different conditions in the marine environment. The water column environmental compartment was simulated under euphotic and aphotic (with and without light availability) conditions. The seafloor environmental compartment was simulated with sediment under non-polluted and polluted conditions. By combining weight loss (%), spectroscopic and thermal analyses, the degradation patterns regarding the polymer structure were assessed. The studied biobased materials were polylactic acid (PLA) based materials and showed higher degradability than conventional ones. The weight loss of conventional materials was not influenced by the water column or sediment, while in PLA-based materials, the degradation rates were ca. 5 times greater in the sediment than in the water column. The absorbance (Abs) value at 3400 cm^-1 for polyethylene terephthalate (PET), and carbonyl (CO) index for PET and PLA could be useful to detect early signs of degradation. The crystallization index could be a useful parameter to discriminate degradation stages. The obtained results highlight the different degradability rates of materials depending on the specific environmental marine conditions.

Keywords: Biobased and biodegradable plastics; Differential scanning calorimetry; Fourier transform infrared spectroscopy; Marine ecosystems; Plastic degradation.