On the effect of using a hybrid of nanoparticles containing clay and CaCO3 on the viscoelastic response of PP/EVA blends Mohammad Mahyar Pourabdollah Khadar1, Javad Seyfi1, Hossein Ali Khonakdar2* 1 Department of Chemical Engineering, Shahrood Branch, Islamic Azad University, Shahrood, Iran 2 Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Strasse 6, D-01069 Dresden, Germany Abstract In this study, polymer blends based on polypropylene (PP) and ethylene-vinyl acetate (EVA) were employed to fabricate nanocomposites containing calcium carbonate (CaCO3) and clay nanoparticles via the melt-mixing method. The main aim is to study the effect of nanoparticles’ hybrid on the rheological properties of PP/EVA blends. Both static and dynamic conditions were utilized for rheological investigation of the prepared samples. Results showed that nanoparticles had different effects on the viscoelastic response of the polymer blend. Those samples containing a fixed amount of clay (5 wt.%) and various amounts of CaCO3 showed a stronger elastic response. The most pronounced enhancement was observed when the content of clay increased from 1 to 5 wt.% upon which the elastic modulus increased from 70 to 750 Pa. The results showed that upon increment of clay content from 1 to 5 wt.%, the dynamic viscosity was also increased from 3000 to 17600 Pa.s, which could hinder the flow-ability of the polymer blend. However, a shear-thinning behavior was detected indicating the sudden drop of viscosity upon increasing the shear rate. In order to support the rheological data, scanning electron microscopy and hardness tests were also performed. Keywords: Viscoelastic response; nanocomposite; polymer blend; clay; calcium carbonate