Depolymerization of poly (L-lactic acid) under hydrothermal conditions

Abstract

Poly (L-lactic acid) (PLLA) was readily depolymerized by hydrolysis under hydrothermal conditions in the absence of catalysts. The optimum condition for depolymerization of PLLA was found to be 220°C and 20 min. Under this condition, the recovery of L-lactic acid was more than 95% without loss of optical purity. At a higher temperature (260-300°C), the optical purity decreased with increasing temperature, and a racemic mixture was formed at 300°C. Based on these results, the method was found to be promising for recycling PLLA by converting it to its monomer, L-lactic acid.