ABSTRACT
Bacterial poly(3-hydroxybutyrate), PHB, and related microbial poly(hy droxy alcanoates), PHA, have attracted much attention as biodegradable and bio compatible thermoplastic polymers [1 ,2]. However, wide-scale applications of bac terial polymers are still prevented by high production cost and some undesirable properties (brittleness, for example). A widespread practice in polymer science to modify physical properties is polymer blending. In the case of PH As, blending also affects biodegradability, and a number of biodegradation studies on PHA-based blends have been recently published [3-8]. It is generally found that when PHAs form miscible blends with nonbiodegradable polymers, biodegradability substan tially decreases [4-7]. However, when the two blend components are immiscible, phase separation occurs and in some cases an increase of PHA biodegradation rate has been found [3-5, 8]. In the presence of water-soluble polymers as second blend components, i.e., poly(ethylene oxide) [3] and starch [8], accelerated degradation was attributed to an increase of surface area exposed to enzymatic attack.
