Evaluation of Rheological Behaviour upon Recycling of an Ethylene Vinyl Acetate Copolymer by Means of Twin-Screw Extrusion Process

Abstract

Recycling of many polymers has gained a spectacular importance mainly because of its environmental and economical benefits. Ethylene vinyl acetate is one of the thermoplastics used directly as a final product and indirectly as an additive within many other polymeric materials. There has been limited research work on recycling of polymers even though recycling in industry has shown a spectacular growth in the last decade. It is the aim of this study to investigate and to evaluate the rheological behaviour of an ethylene-vinyl acetate copolymer resin upon recycling. For this purpose, original ethylene vinyl acetate granules were processed five cycles by using a twin-screw extruder and their rheological analysis was performed by means of an AR-G2 rheometer (TA Instruments), with a parallel-plate geometry, under a steady state condition. It was found that the rheological measurements of copolymer ethylene vinyl acetate exhibited a shear thinning constitutive behavior, obeying Carreau-Yasuda rheological constitutive model. The changes in flow and oscillatory shear measurements under different processing conditions were also determined in detail and results are reported in the paper.