Polypropylene glycol and poly(propylene glycol-ethylene glycol) copolymer as biodegradable plasticizers for polylactic acid

Four new plasticizers for polylactic acid (PLA) were studied. The low molecular weight polypropylene glycol (PPG) and polypropylene glycol end-capped with epoxy groups (PPG-epoxy) were found to be miscible with polylactic acid. The improved mechanical properties of the plasticized PLA remained stable for over a one-year period. The biodegradation tests showed that PPG was biodegradable but PPG-epoxy remained stable during the period of biotesting. No reactions were detected between PLA and PPG-epoxy as determined by GPC and NMR experiments.; The higher molecular weight plasticizers of the poly(propylene glycol-ethylene glycol) block copolymers increased the flexibility and elongation at break of PLA and remained stable for a period of two months. Copolymers were selected to increase the molecular weight of the plasticizer because polypropylene glycol with a molecular weight that is higher than 2000 was found to be immiscible with polylactic acid.; Thermal and dynamic tests revealed that PPG and PPG copolymers were compatible and miscible with PLA. The PEG block in the PPG-PEG copolymers was determined to increase the miscibility of the plasticizers with polylactic acid.