Fabrication and properties of polyvinyl alcohol/starch blend films: Effect of composition and humidity

In this work, starch/polyvinyl alcohol (PVA) blend films with different compositions were prepared by melt processing. The effect of the composition and relative humidity (RH) on the structure and properties of the resulting blends were investigated. OH groups on starch and PVA formed hydrogen bonding interactions, which could improve the compatibility of the two components. With the increase of starch, the degree of crystallinity of PVA component decreased. The fracture surface of the blend films exhibited rough surface, suggesting the tough fracture. With the increase of starch, the water uptake at equilibrium decreased. With the increase of RH, the water uptake at equilibrium of the resulting blends increased. The tensile strength, elongation at break and Young's modulus decreased with increasing content of starch. However, at 50% starch content, the flexibility of the blend films was still high, with the elongation at break more than 1000% and tensile strength of 9MPa, which was superior to the commonly LDPE package films. The tensile strength and Young's modulus decreased with the increase of RH, while the elongation at break was enhanced dramatically, indicating the improved flexibility. Therefore, these kinds of blend films exhibited wide application potentials as packaging materials.