Polymer blending effects on the physicochemical and structural features of the chitosan/poly(vinyl alcohol)/fish gelatin ternary biodegradable films

Films with appropriate mechanical properties and low permeability are very important for food packages. The aim of this research was to develop and characterize the ternary films made from chitosan (CH), poly(vinyl alcohol) (PVA), and fish gelatin (FG) at different blend compositions (50/50/0, 40/40/20, 35/35/30, 30/30/40, and 25/25/50, CH/PVA/FG) via a simple casting method. Stress-strain curves showed that the incorporation of 20% FG into the films made them tougher as well as making them more elastic; optimum ternary films were obtained using CH/PVA/FG ratio of 40/40/20, giving maximum values of TS and EAB as 41.93 +/- 3.24 MPa and 133.13 +/- 13.23%, respectively. The water vapor permeability (WVP) values of the ternary films were in the range of 0.686-0.818 g mm/kPa h m(2). With increasing FG content, the WVP of the films increased to some extent, whereas the water solubility was reduced up to 23%. Water absorption increased with increasing FG concentration up to 874%. Meanwhile, the ultraviolet-visible-light barrier of the resultant ternary films was significantly improved with the addition of FG; at the same time, an increase in FG concentrations also made the films more opaque and improved their thermal stability. FT-IR spectra showed interactions through hydrogen bonding between the polar groups of FG and hydroxyl moieties of CH and PVA in the blends, which enhanced the compatibility between the three polymers. X-ray diffraction analysis suggested compatibility among the polymeric-blends, and changes of the surface of the films was confirmed by SEM and AFM analyses. The obtained results suggested the effectiveness of blending approach in improving the compatibility of polymers and overall functionality of films.