Rapid photo aging of commercial conventional and biodegradable plastic bags

Biodegradable plastic (BPs) bags are introduced and widely used as alternatives to conventional commercial plastic bags in an effort to mitigate the adverse impacts of nondegradable (conventional) plastics. However, being used as packaging, the stability and safeness of the BPs and even the conventional plastics with photo irradiation in short duration remain unknown. In this study, we systematically explored the photo aging of commercial BPs bags and conventional plastic bags in film forms in both outdoor and laboratory experiments in short duration (~ one month) under the scenario of ordinary daily use. Conventional plastic bags (polyethylene (PE)) and BPs bags (hybrids of polylatic acid (PLA) and poly(butylene adipate-co-terephthalate) (PBAT) with additives (Magadiite or Starch)) were investigated. In contrast with the visually negligible surface change of PE films in both outdoor and laboratory environments, obvious surface alteration as surface deterioration with cracks and holes was obtained for BPs from SEM images in direct irradiation by both natural and simulated sunlight. Consistently, AFM results also indicated that the surface of BPs had the tendency to be rougher after photo aging process. Further FTIR and XPS results demonstrated that though the visual surface alteration of conventional and biodegradable plastics are distinct, the mechanisms dominating the change of C-H/C-C bonds to carbon‑oxygen functional groups (i.e., C-O/C=O/O-C=O) for both conventional plastics and BPs during the photo aging process are similar. Moreover, tensile strength tests demonstrated that BPs bags being easily broken compared with the conventional PE bags might attribute to the difference in their mechanical properties. The findings of this study suggest that the potential risk of MPs and NPs released from the BPs bags via photo aging process are great new threats to natural environment and even human health.