Characterization of the degradation products of biodegradable and traditional plastics on UV irradiation and mechanical abrasion

Biodegradable plastics are popular alternatives to traditional plastics in packaging, mulch sheets, and other applications. However, there are concerns regarding the potential for pollution as a result of their abiotic degradation. In this study, we investigated the degradation of biodegradable polybutylene adipate terephthalate/polylactic acid (PBAT/PLA) and traditional polyethylene (PE) plastic under two typical abiotic conditions: ultraviolet (UV) irradiation and mechanical abrasion (MA) for up to nine months. The physical and chemical properties of the two plastics during the degradation period were assessed. In addition, quantitative analysis of the degradation products was carried out using a new method called membrane filtration and total organic carbon determination (MF-TOCD). The results revealed that PBAT/PLA underwent a greater number of changes in surface morphology, thermal stability, and mass loss compared to PE when exposed to UV and MA during the test period. Further analysis of the released products revealed that PBAT/PLA released more products than PE. Overall, PE mainly produced microplastics (MPs) larger than 0.22 μm, whereas PBAT/PLA produced products <0.22 μm (nanoplastics and soluble molecules) on UV exposure. In contrast, when subjected to MA, PBAT/PLA produced MPs larger than 0.22 μm, and these accumulated gradually; this behavior is similar to that of PE. By combining the mass loss and the TOC data for the degradation products, we determined that long-term UV irradiation generated a large number of smaller particles from PBAT/PLA that could further degrade rather than accumulate in the environment. In summary, we established a new method to separate and characterize MPs as well as nanoplastics and soluble molecules, and provided new insights into the fate of PBAT/PLA during abiotic degradation.