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

Depolymerization of poly (L-lactic acid) was conducted under hydrothermal conditions at the temperature range of 160-350 degrees C and for a period of 3 h. The results show that the reaction temperature and time affect the extent of depolymerization and optical selectivity. The optimum conditions on depolymerization of poly (L-lactic acid) were attained at 270 degrees C and 8 min of reaction time. Higher optical purity of L-lactic acid was obtained with a yield of 96%. A Study on the effect of temperature on the optical purity of lactic acid product demonstrated that L-lactic acid was predominant at low range temperature of 250-270 degrees C. At higher temperature, optical purity was reduced and racemization occured. The experimental results showed that the method was found to be simple and promising for chemical recycling of poly (L-lactic acid) into its monomer.