Rheological Behavior of Modified Starch/EVA Blends

There is a current research tendency towards the biodegradable thermoplastic materials from renewable resources since the environmental restraints play vital role in recent years. Starch is one of the renewable resources and abundantly available in the form of plant products. It is possible to blend starch with various thermoplastic materials to achieve such aims. In this study, an ethylene-vinyl acetate (EVA) copolymer resin (Luvax 40 W, DuPont) was blended with a modified starch (Maize Starch, Pendik Nisasta) in various amounts by means of a single screw extruder with different screw speeds. For this purpose, first starch was modified in a four neck spherical glass reactor. Modified starch was then blended with the EVA copolymer resin. Rheological analyses of these composites were performed by means of an AR G2 rheometer (TA Instruments) with parallel-plate geometry in a steady state condition. Rheological behavior and properties were recorded. The changes in viscosity with different temperatures, stress and strain dependence as well as general constitutive material behavior were determined in detail. As a result, the best formulation and process conditions were determined for the reasonable processability of starch/EVA blends from the obtained rheological data