BIODEGRADABLE POLYMER BLENDS OF POLY(LACTIC ACID) AND POLY(ETHYLENE GLYCOL)

Poly(lactic acid) (PLA) and poly( ethylene glycol) (PEG) were melt-ble nded and extruded into films in the PLA/PEG ratios of 100/0, 90/10, 70 /30, 50/50, and 30/70. It was concluded from the differential scanning calorimetry and dynamic mechanical analysis results that PLA/PEG blen ds range from miscible to partially miscible, depending on the concent ration. Below 50% PEG content the PEG plasticized the PLA, yielding hi gher elongations and lower modulus values. Above 50% PEG content the b lend morphology was driven by the increasing crystallinity of PEG, res ulting in an increase in modulus and a corresponding decrease in elong ation at break. The tensile strength was found to decrease in a linear fashion with increasing PEG content. Results obtained from enzymatic degradation show that the weight loss for all of the blends was signif icantly greater than that for the pure PLA. When the PEG content was 3 0% or lower, weight loss was found to be primarily due to enzymatic de gradation of the PLA. Above 30% PEG content, the weight loss was found to be mainly due to the dissolution of PEG. During hydrolytic degrada tion, for PLA/PEG blends up to 30% PEG, weight loss occurs as a combin ation of degradation of PLA and dissolution of PEG. (C) 1997 John Wile y & Sons, Inc.