Nanocompósitos PP/bentonita: efeito das condições de processamento e viscosidade da matriz.

Abstract

This work in concerned with the preparation of nanocomposites from polypropylene and 1% bentonite clay, both natural and organophilic, using the melt intercalation procedure, in different equipments and under different processing conditions. Three grades of polypropylene, with different melt flow rates (between 3.5 and 40 dg/min, ASTM D1238, 330/2.16 condition) were used in the present study. The organic modification of the clay was performed with Cetrimide (dodecyl trimethyl ammonium bromide). The incorporation of the organic modifier was verified by the increase of the interlayer distance in the clay structure and by appearance of the modifier characteristic peaks in infrared spectra. The polymer and clay were compounded in a modular corotating twinscrew extruder, a conical counter-rotating intermeshing twin-screw extruder, and a single-screw extruder fitted with custom mixing section. The compounds were characterized by x-ray diffraction, optical microscopy and mechanical (tensile and impact) properties. X-ray diffraction and microscopy showed that matrix viscosity and processing conditions affected the structure of the compounds; microcomposites and intercalated structures were observed. The results also suggest that the single-screw extruder with the mixing section may be used to make nanocomposites, a fact that – if confirmed by further studies – may be of technological and commercial importance. Mechanical properties of the compounds prepared with organoclay were slightly better that those of polymer matrix.