Morphology and thermal behaviour of poly(3-hydroxybutyrate-co-hydroxyvalerate) starch valerate blends

The morphology, crystallisation and melting behaviour of binary blends prep ared by extruding mixtures containing different amounts of starch valerate (SV) and a poly(3-hydroxybutyrate-co-hydroxyvalerate) copolymer have been i nvestigated by optical and scanning electron microscopy, differential scann ing calorimetry, dynamic mechanical thermal analysis and mechanical tensile tests. The absence of apparent phase separation, the increase in spherulit e dimensions and the decrease of radial growth rate with increasing SV cont ent, as well as the presence of a single composition-dependent T-g value, e videnced a high degree of compatibility between the two components, up to 2 0 wt.-% of SV. For higher SV contents, phase separation occurred, confirmed by the appearance of the T-g values of the pure components in thermal anal yses.