Effect of Processing Conditions on the Development of Morphological Features of Banded or Nonbanded Spherulites of Poly(3-hydroxybutyrate) (PHB) and Polylactic Acid (PLLA) Blends

Two semicrystalline poly(3-hydroxybutyrate) (PHB) and polylactic acid (PLLA) blends with and without poly (vinyl acetate) (PVAc) were prepared by dissolving different ratios in hot chloroform at 50 degrees C to obtain promising alternative biodegradable materials for eliminating plastic waste. The miscibility, crystallization, melting behavior and vibration modes of the prepared samples were characterized by differential scanning calorimetry (DSC), polarized optical microscopy (POM), Fourier transform infrared spectroscopy (FTIR), and wide angle X-ray diffraction (WAXD) techniques. DSC analysis showed that only one crystallization temperature for blends with PVAc (single homogeneous phase) and two crystallization temperatures for blends without PVAc (immiscible blends) were obtained. The POM results indicated that the morphological structures of B-381, B-551, and B-831 samples consist of two types of spherulites (fibrils and banded) which created at different crystallization temperatures. The irrelevant interaction between PHB and PLLA structures was detected from FTIR spectra. The addition of PVAc caused an obvious decrease in the peak position of the carboxyl group C=O from 1752 to 1724 cm(-1) due to dipole-dipole interactions. WAXD indicated that the lattice parameters are changed in blends with PVAc and unchanged without PVAc. Our results indicated that, the PVAc can be used as compatibilizer and improved the compatibility between PHB and PLLA. POLYM. ENG. SCI., 51:2191-2202, 2011. (C) 2011 Society of Plastics Engineers