Basic Properties of Polylactic Acid Produced by the Direct Condensation Polymerization of Lactic Acid

Abstract

Abstract The direct condensation polymerization of lactic acid has been studied, and polylactic acid having a high molecular weight was obtained in an organic solvent without any isolation of the intermediate, dilactide. The molecular weight was raised up to 300000 through the examination of several reaction conditions, e.g., solvent, catalyst, etc. Thus-obtained high-molecular-weight polylactic acid can be processed into films and molded products having sufficient strength and toughness. The characteristic features of polylactic acid obtained by this direct process were compared to that obtained by the conventional ring-opening polymerization process. In addition, copolymerization of lactic acid with a variety of d/l ratios is discussed.