Simulated environmental weathering of expanded polystyrene foam and polypropylene under UV and wave agitation

Improper plastic waste management contributes to environmental accumulation and poses significant risks to marine ecosystems and human health. Once in aquatic environments, plastics undergo weathering, leading to physical and chemical changes and fragmentation into microplastics (MPs). This study examines the weathering of expanded polystyrene (EPS) foam containers and polypropylene (PP) bags under ten simulated conditions including UV exposure in dry and wet environments (seawater and deionized water), with and without artificial waves. Surface changes were assessed using stereo microscopy, scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). EPS foam exhibited discoloration, surface cracking, and fragmentation, particularly under UV exposure. These effects were pronounced in both dry and wet environments and confirmed by SEM imaging. PP showed gradual surface changes and fragmentation only under UV exposure with wave agitation, mainly in dry and seawater conditions, without clear discoloration. Carbonyl index (CI) analysis indicated more advanced chemical degradation in EPS foam compared to PP. FTIR spectra revealed new peaks corresponding to C = O and O-H bonds, consistent with photo-oxidative degradation. These results highlight material-specific weathering behaviors and underscore the roles of UV radiation and hydrodynamics in accelerating secondary MP formation, emphasizing the need for comprehensive plastic waste management strategies.