Effects of irradiation and aging on the molecular and phase structure of poly(L-lactide): insights into degradation and recycling potential

The impact of high-dose e-beam and γ-irradiation, followed by long-term aging, on the structural properties of poly(L-lactide) (PLA) was investigated. Due to prolonged exposure, γ-irradiation caused more extensive oxidative degradation, accelerating the aging process compared to e-beam irradiation. Aging effects were most pronounced in samples irradiated at doses exceeding 600 kGy. Structural analysis using ¹ H NMR revealed distinct mechanisms of chain scission during irradiation and aging, resulting in the formation of different end groups. Irradiation induced deterioration of PLA’s phase structure occurred during irradiation was observed, including the formation of conformationally disordered α’ crystalline form. Aging at doses exceeding 1000 kGy led to amorphization. The degradation behavior of aged PLA in water and its recycling potential were also evaluated. While partial dissolution of aged samples occurred in a short term, further degradation was hindered by water induced crystallization. Unirradiated and low-dose irradiated PLA demonstrated promising recyclability to lactide, highlighting its potential for industrial-scale chemical recycling as a sustainable alternative to landfilling or composting.