The design of the screw configuration as well as the screw speed, the residence time, the feeder type, and the temperature has a large effect on the dispersion of the clay into the matrix and, consequently, on the mechanical and thermal properties of the polymeric matrix. The objective of the present work was to evaluate the influence of two different screw configurations (left-handed elements) and the feed type (hopper or side feeder) on the dispersion of 5 wt% Cloisite 20A into the PP matrix without the use of compatibilising agents. In profile 1 (lower shear), the 5 wt% C20A/PP (PPC20AP1) nanocomposite morphology presented elliptical agglomerated structures with compacted platelets, whereas in the profile 2, the 5 wt% C20A/PP (PPC20AP2) showed elongated forms with better separated platelets and a better clay distribution into the PP matrix. When the side feeder mode was used in profile 2, a mix of elliptical and elongated structures with some individual clay sheets was observed.The neat PP showed the same tensile modulus and impact strength in both screw configurations. The PPC20AP1 presented a tensile modulus and an impact strength that was lower than the PPC20AP2, because in profile 2 the pressure and residence time are higher due to the two left-handed elements. Thus, the dispersion and distribution of the clay throughout the matrix were improved, and the agglomerated structures were reduced. When the side feeder mode was used, there was a decrease in the PP/clay mechanical properties, but the values found were higher than those in profile 1.
PP nanocomposites; processing conditions; properties; morphology
