Solvent-Assisted Poly(lactic acid) Upcycling under Mild Conditions

Poly(lactic acid) (PLA) is a biosourced green plastic derived from natural sources that can replace polyolefins in many applications; however, it is seldom recycled. PLA is a prime candidate for chemical recycling by depolymerization, which produces valuable commodity chemicals and/or fresh monomer for new production, compared to mechanical/thermal reprocessing which produces lesser-quality resin. A scalable, low-cost depolymerization process could render PLA the premier choice for designed-to-be-recycled products in a future circular plastics economy. Here, we report a novel process for depolymerization of PLA under mild conditions using alcoholysis with ionic liquid catalysts in the presence of dimethyl (or diethyl) carbonate as a green solvent, along with critical technoeconomic analysis of the potential impact of this process. The effects of catalyst structures, the solvent system, and PLA resin type on conversion and yield were studied. The reaction kinetics were statistically analyzed with experimental and modeling data, suggesting a fast first-order reaction in PLA degradation. Predictive modeling results based on empirical data further guide the design of scenarios and potential for practical application.