A series of polypropylene (PP) nanocomposites containing 2, 4, and 6 wt % of an organophilic montmorillonite clay was prepared via direct melt mixing in the presence of maleic anhydride grafted polypropylene (PP-g-MAH) as compatibilizing agent. Microstructure characterization was performed by X-ray diffraction analysis. Nanocomposites exhibited a 15 and 22% enhancement in tensile modulus and impact strength, respectively. The heat deflection temperature of PP nanocomposites was 36 degrees C greater than for pure PP. Thermal and mechanical properties of nanocomposites were compared to properties of traditional PP-talc and PP-glass fiber composites. The results showed that the properties of nanocomposites improved compared to ordinary polypropylene composites. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 113: 922-926, 2009