BIODEGRADABLE POLYMER BLENDS OF POLY(3-HYDROXYBUTYRATE) AND STARCH ACETATE

The thermal behaviour and phase morphology of poly(3-hydroxybutyrate) (PHB) and starch acetate (SA) blends have been studied by differential scanning calorimetry, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy and polarizing optical microscopy. PHB/S A blends were immiscible. The melting temperatures of PHB in the blend s showed some shift with increase of SA content. The melting enthalpy of the PHB phase in the blend was close to the value for pure PHB. The glass transition temperatures of PHB in the blends remained constant at 9 degrees C. The FTIR absorptions of hydroxyl groups of SA and carb onyl groups of PHB in the blends were found to be independent of the s econd component at 3470 cm(-1) and 1724 cm(-1), respectively. The crys tallization of PHB was affected by the addition of the SA component bo th from the melt on cooling and from the glassy state on heating. The temperature and enthalpy of non-isothermal crystallization of PHB in t he blends were much lower than those of pure PHB. The crystalline morp hology of PHB crystallized from the melt under isothermal conditions v aried with SA content. The cold crystallization peaks of PHB in the bl ends shifted to higher temperatures compared with that of pure PHB.