Characterization of accelerated degradation of low density polyethylene containing pro-degrading agents by X-ray photoelectron spectroscopy

Full text: Several short lifetime products are based on polyolefins, i.e. low density polyethylene (LDPE), which are inappropriately disposed after use. They are decomposed by the influence of abiotic climatic agents, which it takes hundreds of years [1]. There has been an increase negative environmental impact, which can be minimized with the adoption of additives that accelerate the degradation of plastic materials. Thus, this study aims to assess the accelerated degradation of LDPE containing pro-degrading agents by means of X-ray photoelectron spectroscopy (XPS). LDPE films have been processed by extrusion, where 1% prodegrading agent in mass was added. The agents are derived from salts as basis of cobalt, aluminum, cerium, calcium, zinc and glyceryl. They have been individually incorporated into the molten polymer. Accelerated aging has been conducted in a UV chamber with a temperature of 60 °C for 15 days. Subsequently, XPS analyzes were conducted on the samples before/after aging and the atomic content for oxygen and carbon was determined in three different parts of each sample. Degradation happens when the carbonic chain breaks and oxygen content increases due to oxidative route. In this way, it was possible to follow the degradation process, by monitoring the breakdown of the carbon chain and the increase of molecular oxygen. The results showed that samples modified with metal-based additives have shown increased content of oxygen after aging, in the order Al > Ce > Zn > Ca > Co. Glyceryl-modified LDPE have not presented significant statistical variation on the oxygen content. This suggests that all the studied metal salts added to LDPE matrix caused the polymer to oxidize during UV light exposure. [1] BARBOSA, LA. et al. Espacios 38, 10 (2017).(author)