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Thermal, Crystallization, and Biodegradation Behavior of Poly(3-hydroxybutyrate) Blends with Poly(butylene succinate-co-butylene adipate) and Poly(butylene succinate-co-ε-caprolactone)

Morphologies, some physical properties, and biodegradability were investigated for the binary blends of natural poly(3-hydroxybutyrate) [P(3HB)] with chemosynthetic poly(butylene succinate-co-butylene adipate) (PBSA) and poly(butylene succinate-co-ε-caprolactone) (PBSC) prepared using a simple casting procedure. The DSC thermogram of each blend system revealed two distinct glass transitions independent of blend composition. The radial growth rate of P(3HB) spherulite in the blends, observed on a polarizing microscopy, almost kept constant in the blends with P(3HB) content ranged from 50 wt% to 100 wt%. These results indicate that P(3HB) and PBSA, and P(3HB) and PBSC are immiscible in the amorphous state. The enzymatic degradation of blend film was carried out in phosphate buffer (pH 7.5) at 37°C in the presence of P(3HB) depolymerase purified from Alcaligenes faecalis T1. The degradation behavior of blends was monitored by observing UV spectra, measurement of weight-loss and NMR analysis. As a general, the weight-loss rates of blends increased with the increase of P(3HB) content except the blends contained 90 wt% P(3HB) in which a weight-loss was about three times faster than that of pure P(3HB) films. After the beginning of degradation, the content of P(3HB) in films decreased faster than those of blend partners. The biodegradability of aliphatic polyester is suggested to be controllable by blending.