Photoaging processes and mechanisms of polyolefin microplastics

Abstract

The photoaging processes of microplastics (MPs) under various conditions, including environmental factors and soluble organic matter, have been extensively investigated. However, a notable gap exists in the literature regarding comparative experiments on the photoaging of polyolefin-type MPs, and research on different light sources is particularly scarce. This research involved exposing representative MPs (polystyrene (PS), polyvinyl chloride (PVC), and polyethylene (PE)) to light with different wavelength ranges (200–2000 nm and 320–780 nm). Results indicated that PS and PVC, with benzene rings and C-Cl chains, exhibited higher susceptibility to photoaging compared to PE, leading to changes in physicochemical properties. In 200–2000 nm, including UVC (200–280 nm) and UVB (280–315 nm), a pronounced PS and PVC photoaging process was observed due to their higher energy, which resulted in noticeable yellowing of the morphology. PE showed less pronounced effects, except for noticeable aging in the 320–780 nm range within 6 h (UV–vis spectrum), with a slow depolymerization rate over 72 h. Furthermore, a limited aging of polyolefins was observed under dark conditions. In summary, this study provides crucial insight into the accelerated photoaging of polyolefin-type MPs under different light source, which offers novel perspectives and references for future research directions.