Efeito do desenho da rosca e das condições de processamento em nanocompósitos de polipropileno/bentonita.

Abstract

In this work the effects of processing conditions (screw profile, temperature profile and extrusion speed) on the mechanical properties of PP/organobentonite nanocomposites processed by single srew extrusion were ascertained. Two screws with different profiles wee used to process the samples: 1) a standard screw (RC) and 2) a specially designed screw with mixing elements (RE). Nanocomposites with nominal 1% w/w clay content were single screw extruded and the effective clay content present in the nanocomposites was determined by calcination. The systems were tensile and impact tested and characterized by optical microscopy and X-ray diffraction (XRD).The data did not show significant improvements in nanocomposite mechanical properties, indicating the need for a compatibilizing agent. Calcination evinced that the amount of clay effectively incorporated into the systems was smaller than the nominal amount added. Optical microscopy revealed that better clay dispersion was achieved in the systems processed with the special screw (RE). X-ray diffraction indicated that irrespective of processing temperature profile (180 or 240°C) adopted, intercalated structures were achieved only with the samples processed using the RE screw operating at high shear rates (120rpm). Conventional microcomposites were obtained with all other processing conditions adopted (low shear rates and conventional (RC)single screw extrusion).