Biodegradable films from PHB-8HV copolymers and polyalcohols blends: crystallinity, dynamic mechanical analysis and tensile properties

Blends of poly(3-hydroxybutyrate)-poly(3-hydroxyvalerate) (PHB-HV) and polyalcohols have been prepared by solvent casting. The polyalcohols used were castor oil (CO) and polypropylene glycol (PPG400 and PPG1000). Thermal behaviour, crystallinity, morphology and dynamic mechanical properties of systems with various PPG1000 compositions have been studied. Crystallinity was determined by means of Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction. Final morphology was studied by means of scanning electron microscopy (SEM). Dynamical mechanical analysis showed two glass transition temperatures for the blends, corresponding to separate phases of PHB-HV and polyalcohols. Blend immiscibility was found. Polyalcohol addition enhances the crystallinity of PHB-HV. However, the storage modulus value decreases, upon the addition of amorphous compound.