studies on different properties of composite thin films made from waxy starch-citric acid and starch-methyl cellulose

pollution arising from plastic waste materials caused a great worry for researchers who are interested in protection of environment. this problem shifts their subject to bio-polymers for applications in packaging industries. however, their low water barrier properties are a critical problem. the effects of citric acid and methyl cellulose on water vapor and oxygen permeabilities and mechanical properties of starch composite thin films have been studied. water vapor permeability (wvp) has been measured using a vial coated by a film. oxygen transmission rate (otr) of a film was determined from measurement of peroxide value for a definite amount of oil that is placed in a vial and coated by the film. mechanical properties were measured using a tensile machine. increase in citric acid concentration up to 5% citric acid (w/w), resulted in a decrease in water vapor and oxygen permeabilities. a film containing 5% of citric acid exhibited a minimum value for wvp, whereas the value of wvp and elongation at the break increased and tensile strength decreased for a film containing 20% of citric acid (w/w). increase in methyl cellulose up to 30% resulted in decrease in wvp and otr.