Assessment of PLA Depolymerization for Circular Economy: Production Pathways, Physical Properties, Thermodynamics, and Kinetic Modeling

Polylactic acid (PLA) is a biopolymer that offers an alternative to petrochemical-based plastics. Considering the market share growth of PLA and assessing sustainability, there is a need to model PLA production pathways. This work presents a comprehensive evaluation of the conventional production of PLA from lactic acid via lactide, including its chemical recycling. We outline key processing steps─prepolymer formation, lactide synthesis and refining, and ring-opening polymerization─highlighting the critical roles of stereochemistry, mass and heat transport, and catalysis. We introduce physical property modeling relevant to separation and purification units. We develop a fundamentally consistent kinetic model based on known equilibrium relationships and ring–chain kinetics for condensation polymers. We present a combined kinetic model suitable for ring-opening polymerization, PLA hydrolysis, solvent-free depolymerization, racemization, and thermal degradation. This work advances a modeling framework that can be used for PLA manufacturing and recycling processes and identifies key knowledge gaps to guide future PLA research.