Effect of artificial UV-thermal ageing on the structural and mechanical properties of PLA and PBAT

This article is devoted to the study of the degradation of two widely used biodegradable polymers, polylactic acid (PLA) and poly(butylene adipate-co-terephthalate) (PBAT), which are in demand in packaging, medicine, and agriculture.The effect of ultraviolet radiation (UV) at elevated temperatures on polymer ageing was investigated for 24, 120, and 240 h using a specially designed setup.Scanning electron microscopy, Fourier transform infrared spectroscopy, and tensile testing were employed to provide a comprehensive assessment of changes.PLA showed rapid degradation: after 120 h, its surface developed cracks and voids, and at 240 h, it became heavily damaged with cavities.PBAT degraded more gradually: at 240 h, large cracks and cavities were observed.For PLA, early ageing led to a shift and broadening of the carbonyl band, reflecting disorder and ester scission.For PBAT, a decrease in the intensity of the carbonyl shoulder and a slight shift of the main peak at elevated temperature indicated phase redistribution and the formation of new functional groups.Mechanically, PLA exhibited a sharp loss of strength and ductility in the first day of ageing, while PBAT showed greater stability, with slower reductions in stiffness and strength but a strong temperature-dependent decline in elongation.These findings are important for guiding the design of biodegradable polymers with improved durability.