Investigation of morphological, rheological, and mechanical properties of cyclic olefin copolymer/poly(ethylene-co-vinyl acetate) blend films

In this study, cyclic olefin copolymer/poly(ethylene-co-vinyl acetate) 90/10, 80/20, and 70/30 blends were prepared by melt processing in a twin screw extruder equipped with a cast film haul-off unit to make films. Microstructural, rheological, mechanical, and viscoelastic properties of film samples were investigated by various tests performed in scanning electron microscope, rotational rheometer, dynamic mechanical analyzer, and tensile test machine. We observed that the films exhibited characteristic immiscible matrix-droplet or cocontinuous blend morphology, depending on the sample composition. Based on the melt rheology and dynamic mechanical analyzer tests, we found that poly(ethylene-co-vinyl acetate) addition changed the viscoelastic properties of cyclic olefin copolymer such as increasing short-term creep strain and relaxation time but reducing relaxation rate in solid state. One can conclude that such effects became more pronounced by adding a compatibilizer (PE-g-MA) at 50% of poly(ethylene-co-vinyl acetate) present in the composition. We also found that poly(ethylene-co-vinyl acetate) addition into cyclic olefin copolymer reduced the Young's modulus and yield stress and increased the strain at break for the blends.