Effect of Polyvinyl Alcohol on Cassava and Potato Starch Plastic Film: Mechanical, Thermal and Swelling Properties

Abstract

Uncontrolled use of synthetic plastic has triggered environmental concern due to the decomposition issue that are still not highly efficient and relatively lead to the production of high plastic waste. Due to these circumstances, biodegradable plastic film from natural polymers like cassava and potato starch is developed. However, the brittleness and low mechanical strength of starch based plastic film has contributed to the development of polymer blending between starch and polyvinyl alcohol (PVA) to produce starch/PVA bioplastic film. By using casting method, different proportion of 4% PVA (30% and 60% based on starch weight (dry basis)) solution was added into the starch film-forming solution and the effect of PVA content to cassava and potato starch bioplastic films was studied. After several analysis, it was found that the increment of PVA reduce the thickness of both cassava and potato starch bioplastic films, while at the same time increase the moisture content, swelling capacity and biodegradation rate of this biodegradable films. In addition, bioplastic films from cassava starch shows the higher swelling capacity and biodegradation rate than potato starch plastic film due to its increment in hydrophilicity after blending with PVA. It is also shown that the tensile stress for cassava plastic film increases significantly (p<0.05) when 60% of PVA were added into the formulation. In FTIR analysis, there were existence of C-H stretching in that present in PVA and starch and OH group and C-O-C stretching that could enhance the properties of films by forming hydrogen bonding network. Besides that, the Tg of starch bioplastic decreased with the increased of PVA content due to increment of hydrophilicity of bioplastic films.  Last but not least, the effect of glycerol as plasticizer in this starch films formulation did help in reducing the brittleness of films and prevent the tearing during peeling process. Therefore, the addition of polyvinyl alcohol in cassava and potato starch films may have the potential to be used as bioplastic for the betterment of future waste management.