BIODEGRADATION OF POLY-D,L-LACTIC ACID POLYURETHANES

The relationship between the biodegradability of poly-D,L-lactic acid (PLA) polyurethane compounds and their polymer composition was investi gated. The biodegradability (weight loss) by fungi of these polyuretha nes increased when: 1) the polymethylene polyphenyl polyisocyanate con tent of the polyurethane was reduced; 2) the molecular weight of the p olyethylene glycol moiety in the polyol was increased; 3) the lactic a cid content of the polyol was decreased. Proton NMR analysis of polyur ethanes before and after biodegradation showed that the weight loss of PLA polyurethanes is mainly due to biodegradation of the polyol segme nt within the polyurethane. Measurement of oxygen consumption during c ultivation of fungi indicated that only the polyol of PLA polyurethane s can be biodegraded to CO2. However, a strain of microorganism capabl e of biodegrading a urethane compound (bisethylurethane of tolylene-2, 4-diisocyanate) was isolated, and it was demonstrated that this compou nd was biodegraded in part via intermediates to tolylene-2,4-diamine.