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Investigation of the addition of nano-CaCo3 at dry mixing or onset of fusion on the dispersion, torque, and mechanical properties of compounded PVC



A Brabender torque rheometer equipped with an internal mixer was used to study the influence of compounding method on the properties of (rigid PVC)/(treated and untreated nano-CaCO3) nanocomposites. Two different methods were studied for the addition of surface treated and untreated nano-CaCO3 during the melt mixing of rigid PVC. Direct dry mixing of rigid PVC and nano-CaCO3, and addition of nano-CaCO3 at the onset of PVC fusion were investigated. Dispersion of treated and untreated nano-CaCO3 was studied by X-ray diffraction and scanning electron microscopy. Results showed that using direct dry mixing improved the dispersion of nano-CaCO3 in the PVC matrix by lowering the fusion time. The mechanical properties of the nanocomposite samples such as impact strength, tensile strength, and elongation at break were improved by using this method. The addition of treated nano-CaCO3 at the onset of fusion caused a simultaneous decrease in torque. Also, rigid PVC nanocomposites prepared with treated nano-CaCO3 showed better mechanical properties than those of nanocomposites prepared with the untreated nano-CaCO3. J. VINYL ADDIT. TECHNOL., 18:153–160, 2012. © 2012 Society of Plastics Engineers