Microstructure and on-line shear viscosity of PP/nano-CaCO3 composites prepared by twin-screw extruder

The PP/nano-CaCO3 composites were prepared using a twins-crew extruder. The screw elements were selected and arranged to provide shear intensity and help decrease the aggregation of the nano-CaCO3 and five kneading block sections alternate with the common conveying elements along the screw. A reverse kneading block was set in the second kneading block section to increase the filled degree in the screw elements. The addition of two neutral kneading elements extended the residence time of materials and further increases the shear intensity. The TEM photomicrographs show that high shear intensity screw configuration favors to the dispersion of the nano-CaCO 3. The on-line melt shear viscosity, in addition, of the nanocomposites with the nano-CaCO3 content less than 5 wt% is lower than that of pure PP. Results show that the viscosity of the nanocomposites with the percentage higher than the critical one and is lower than that of polymer matrix.