Study of some physical properties of biodegradable films based on blends of gelatin and poly(vinyl alcohol) using a response-surface methodology

The aim of this work was to study the effect of the hydrolysis degree (HD) and the concentration (C_PVA) of two types of poly(vinyl alcohol) (PVA) and of the type (glycerol and sorbitol) and the concentration (C_P) of plasticizers on some physical properties of biodegradable films based on blends of gelatin and PVA using a response-surface methodology. The films were prepared with a film forming solutions (FFS) with 2 g of macromolecules (gelatin+PVA)/100 g de FFS. The responses analyzed were the mechanical properties, the solubility, the moisture content, the color difference and the opacity. The linear model was statistically significant and predictive for puncture force and deformation, elongation at break, solubility in water, moisture content and opacity. The C_PVA affected strongly the elongation at break of the films. The interaction of the HD and the C_P affected this property. Moreover, the puncture force was affected slightly by the C_PVA. Concerning the solubility in water, the reduction of the HD increased it and this effect was greater for high C_PVA values. In general, the most important effect observed in the physical properties of the films was that of the plasticizer type and concentration. The PVA hydrolysis degree and concentration have an important effect only for the elongation at break, puncture deformation and solubility in water.