Miscibility and biodegradability of blends of poly(lactic acid) and poly(vinyl acetate)

Poly(lactic acid) (PLA) was melt blended with poly(vinyl acetate) (PVA) using a single-screw extruder. The extruded films obtained were characterized for miscibility, physical properties, degradation and surface morphology. Differential scanning calorimetry showed that all the as-extruded films were amorphous, and that the blends were compatible as only one glass transition temperature was observed. Results obtained from physical property testing indicated that the blends exhibit synergism in the range of 5 to 30% PVA, probably due to some interactions taking place in that region. Enzymatic degradation studies showed that there was a vast difference in the weight loss of pure PLA samples and the 95/5 PLA/PVA blend. Surface tension results showed that this was due to the vast difference in the surface tension of the pure PLA films and the 95/5 blend. Deaged-free blends showed the maximum degradation, followed by aged-extruded and then deaged-fixed. Scanning electron micrographs showed that the mode of degradation differs for the aged and deaged samples. A uniform degradation pattern was seen in the case of deaged samples while the aged samples showed a non-uniform pattern of degradation.