Efficient Microwave-Assisted Hydrolytic Recycling of Poly(L-Lactic Acid)

Poly(L-Lactic acid) (PLLA) is a bio-based and biodegradable thermoplastic polymer widely recognized as a leading sustainable alternative to conventional petroleum-based plastics. While its environmental benefits are well established, PLLA faces challenges in end-of-life management due to its slow degradation in natural conditions and the harsh requirements of industrial composting. This study introduces an efficient chemical recycling strategy for PLLA based on hydrolysis reactions performed both in solution and under solvent-free conditions, catalyzed by a homoleptic phenoxy-imine pyridine zinc complex. Both conventional and microwave-assisted heating methods were evaluated. Hydrolysis in solution exhibited consistent degradation rates across various solvents, irrespective of the heating technique. In contrast, microwave-assisted heterogeneous hydrolysis significantly improved both reaction rate and selectivity. Notably, this process enables the direct conversion of postconsumer PLLA products into lactic acid under mild reaction conditions, without the need for additional solvents or pressure build-up. The catalytic approach demonstrates a scalable, energy-efficient pathway for closing the PLLA lifecycle, offering a viable solution for industrial monomer recovery with low waste generation.