Physical properties of ethylene vinyl acetate copolymer and starch blends as biodegradable hot melt adhesive

Abstract

The main objective of this research was aimed to study performance of the preparation and the physical properties of ethylene vinyl acetate copolymer and starch blends as biodegradable hot melt adhesive in packaging application. In batch mixer, the hot melt compositions contained 20% of modified starch and native starch were melt blended with EVA copolymer in order to study the effect of starch on torque and melt temperature. The results indicated that torque was higher for the blends of modified starch compared to native starch. Torque increased with increasing starch content in blends. The process parameters had no effect on tensile strength but they effected on tensile modulus and elongation of HMAs. In twin screw extruder, the concentrations of starch in blends at 10, 20, 30, 40 and 50% by weight were applied. From the result, it was shown that starch acts as organic filler material of choice in the formulation. The starch addition in hot melt formulation had a tendency to reduce tackiness. At 20% of starch, the T-peel strength of 30-40% was decreased. Scanning electron micrographs revealed that starch granule remained and had good dispersed in matrix at 10-20% starch content. The DSC thermographs revealed phase separation for all formulations. The viscosity of starch additional HMAs were lower than those of the corresponding EVA-based HMA and decreased with increasing starch content. The optimum formulation consisted of 30% of EVA, 20% of modified starch, 40% of rosin, 10% of polyethylene wax and 0.25% of BHT. Starch helped to improve in cost of HMAs manufacturing and EVA/starch-based HMAs supported the growth of microorganisms.