Heat-Sealing Properties of Soy Protein Isolate/Polyvinyl Alcohol Film Made Compatible by Glycerol

Heat-sealing properties are necessary for packaging materials. Soy protein isolate/polyvinyl alcohol (SPI/PVA) blend film is a biodegradable potential packaging material. We analyzed the effects of PVA content (0-20%), glycerol content (1-3%), and sealing temperature (180-230 degrees C) on the heat-sealing properties of SPI/PVA blend film. Results showed that SPI/PVA film obtained the desired sealing properties when the PVA content exceeded 15%. The sealing strength increased with the PVA content, reaching a maximum upon blending with 20% PVA and 1% glycerol at 220 degrees C. The temperature at sealing strength was approximately twice that at 180 degrees C. However, glycerol migrated to the surface and hindered the entanglement of macromolecular chains in the sealing interface, thereby resulting in reduction of seal strength. Glycerol vaporization at 204 degrees C led to aesthetically unacceptable blistering in the sealing area. Therefore, the optimum sealing temperature of the blended film was approximate to 200 degrees C. (c) 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40308.