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 du -ration remain unknown. In this study, we systematically explored the photo aging of commercial BPs bags and conven-tional 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, obvi-ous 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 vi-sual 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.

Automated summary

This study systematically investigated the photo aging process of biodegradable plastic (BPs) bags and conventional plastic bags under ordinary daily use conditions. The results demonstrated that BPs bags experienced significant surface deterioration and roughening when exposed to natural and simulated sunlight, while the visually negligible surface change was observed for conventional plastic bags. The mechanisms dominating the change of bonding structures during the photo aging process were found to be similar for both types of plastics. Furthermore, BPs bags were found to be more prone to breakage compared to conventional plastic bags.