Biodegradability of poly(3-hydroxybutyrate) blended with poly(ethyletle-co-vinyl acetate) or poly(ethylene oxide)

Biodegradability of poly(3-hydroxybutyrate) (PHB) was determined by the modified Sturm test utilizing, activated sludge, or synthetic sludge and the result was more reproducible when the activated sludge was used as the microbial source. As PHB was blended with miscible poly(ethylene-co-85 wt% vinyl acetate) (EVA85), biodegradability of PHB was drastically reduced with the addition of EVA85. On the other hand, the biodegradation rate of the immiscible PHB/poly(ethylene-co-70 wt% vinyl acetate) (EVA70) blend was decreased gradually with an increase in the EVA70 content. Almost same biodegradation behavior was observed both for the PHB/EVA85 blend prepared by hot pressing of precipitation from chloroform solution into hexane and for the blend obtained by chloroform solvent casting. However, biodegradability of the PHB/poly(ethylene oxide) (PEO) blend was decreased rather slowly with an increase in the PEO content, even though it was a miscible blend. (C) 1999 Elsevier Science Ltd. All rights reserved.