The insertion of the aliphatic diamine inside the organoclay will help the dispersion of the clay platelets in the PP/clay nanocomposite due to the reaction between the maleated PP and the diamine. Cloisite (R) 20A was just simply mixed with hexamethylene diamine (HMDA) under shearing condition in Brabender mixer. HMDA group was successfully penetrated into silicate layers. As a result of penetration, d-spacing of organoclay was increased. Polypropylene/clay nanocomposites were prepared by compounding with maleated PP and amine-treated clay. From the FTIR spectra, reaction between amine group and maleic-anhydride group was confirmed. The effect of the organoclay on the properties of the nanocomposite such as the morphology, dynamic mechanical properties, crystal structure and crystallization behavior, glass transition temperature, thermal stability, and tensile properties were investigated and analyzed. Nanocomposites with amine-treated clays show enhanced properties compared with those with non-amine-treated clay (Cloisite (R) 20A). From the TEM analysis, nanocomposites with amine-treated clays shows better dispersibility compared with those with Cloisite (R) 20A alone. (C) 2009 Wiley Periodicals, Inc. I Appl Polym Sci 113: 1539-1549, 2009