High performance films obtained from PVA/Na2SO4/H2O and PVA/CH3COONa/H2O systems

The atactic poly(vinyl alcohol) (a-PVA) aqueous solutions with Na2SO4 or CH3COONa were cast to prepare films and then the Na2SO4 or CH3COONa in the films was removed. Both films prepared by removing Na2SO4 or CH3COONa in water had a water-resistance property. The degree of crystallization of the films increased with an increase of the contents of Na2SO4 and CH3COONa in the solutions up to 0.05 and 0.1 wt%, respectively. However, the melting temperature (226–228°C) was independent of the content of Na2SO4 and CH3COONa in the solutions. The draw ratio and tensile modulus of the films prepared from the solutions with 0.01 wt% Na2SO4 and 0.1 wt% CH3COONa were 1.3–1.6 times more than that of the films obtained from an aqueous solution. Namely, in case of the films obtained from a-PVA/H2O/Na2SO4 and a-PVA/H2O/CH3COONa systems, both the drawability and mechanical properties as well as the degree of crystallization were higher than those for the film obtained from an aqueous a-PVA solution.