In this work, polypropylene-commercial montmorillonite organophilic clay nanocomposites were prepared using a Werner Pfleiderer twin-screw extruder. Considering the nonpolar characteristic of the polypropylene, polypropylene-graft-maleic anhydride (PP-g-MA) was used as a coupling agent to improve the intercalation process into the layers of montmorillonite. The materials containing 2.5, 5.0, 7.5 and 10.0% of the clay (N2.5, N5, N7.5 and N10) and PP and two extra compositions containing only PP and 15.0 and 30.0% of PP-g-MA (PP, P15 and P30), respectively, were investigated upon the nanocomposites structures. The properties of materials were characterized by X-ray diffraction (XRD), SEM analysis and reflectance spectrophotometry. The X-ray diffraction showed exfoliated or intercalated structure for different concentrations; the SEM analysis showed a good dispersion of the clay in the PP matrix and the spectrophotometric analysis showed that the amount of clay used in the compositions resulted in different levels of opacity. (c) 2006 Elsevier B.V. All rights reserved.44741671261265