Starch/polyvinyl alcohol blends containing polyurethane as plasticizer

Abstract

Starch-based films containing 70wt% of starch and a combination of poly(vinyl alcohol) and a low glass transition temperature polyurethane as plasticizer were prepared. The effect of PVA/PU ratio content on the morphology and physical properties was investigated by infrared spectroscopy (FTIR), X-ray diffraction, differential scanning calorimetry, thermogravimetric analysis, scanning electron microscopy and measurements of mechanical properties and water vapor permeability. A relative small amount of PU (less than 15 wt%), significantly changes the properties of the blend due to intermolecular hydrogen bonding interactions between the three components. FTIR and XRD results indicate that blends containing PU are more amorphous than the pure starch/PVA blend and SEM images show a homogeneous matrix due to the good compatibility between starch and PU. Incorporation of PU to the starch/PVA blend shifts the glass transition temperature to lower values and reduce the elastic modulus, indicating a successful plasticization effect. The resulting blends produce films with improved physical properties.