High Molecular Weight Polylactic Acid Polymers

Abstract

Polylactic acid (PLA) belongs to the family of aliphatic polyesters commonly made from α-hydroxy acids which include polyglycolic acid, [1, 2] or polymandelic acid [3] and are considered biodegradable and compostable. PLA is a thermoplastic, high strength, high modulus polymer which can be made from annually renewable resources to yield articles for use in either the industrial packaging field [4] or the biocompatible/bioabsorbable medical device market [5]. It is easily processed on standard plastics equipment to yield molded parts, film, or fibers. It is one of the few polymers in which the stereochemical structure can easily be modified by polymerizing a controlled mixture of the L or D isomers to yield high molecular weight amorphous or crystalline polymers which can be used for food contact and are generally recognized as safe (GRAS)[6]. PLA is degraded by simple hydrolysis of the ester bond and does not require the presence of enzymes to catalyze this hydrolysis. The rate of degradation is dependent on the size and shape of the article, the isomer ratio, and temperature of hydrolysis. A more detailed summary of degradation and lactic acid manufacturing is given in recent monographs [7, 8].