Microplastic Formation From Biodegradable PLA / PBS Films Under Accelerated Ultraviolet‐C Aging in Aqueous Environments

Biodegradable polyesters such as polylactide (PLA) and polybutylene succinate (PBS) are increasingly used in packaging, yet the effect of photochemical pre‐aging on their subsequent fragmentation into microplastics remains insufficiently understood. This study investigated PLA, PBS, and PBS/PLA blends subjected to controlled ultraviolet‐C (UVC) pre‐aging (254 nm, 3 h) followed by 12 weeks of exposure to Milli‐Q water or seawater. UVC treatment increased crystallinity from 3.1% to 11.6% in PLA and from 55.6% to 77.2% in PBS and markedly reduced ductility; for PBS/PLA 70/30, elongation at break decreased from 65% to 13%. Subsequent fragmentation was strongly composition‐dependent: PLA and PLA‐rich blends generated smaller and more numerous fragments, whereas PBS retained larger fragments, with blends showing a gradual transition between these behaviors. Optical microscopy revealed particles spanning from the micrometer to millimeter range. Milli‐Q water and seawater produced comparable overall fragmentation trends, while the pH of Milli‐Q water decreased from 6.4 to approximately 4.0 for all blends. These results support the relationship between UVC‐induced embrittlement and subsequent fragmentation and demonstrate that biodegradable polyester films can generate microplastic‐sized particles before complete mineralization.