The melt mixing technique was used to prepare various polypropylene (PP)-based (nano)composites. Two commercial organoclays (denoted 20A and 3013) served as the fillers for the PP matrix, and two different maleated (so-called) compatibilizers (denoted PP-MA and SMA) were employed as the third component. The results from X-ray diffraction (XRD) and transmission electron microscope (TEM) experiments revealed that 190 degreesC was an adequate temperature for preparing the nanocomposites. Nanocomposites were achieved only if specific pairs of organoclay and compatibilizer were simultaneously incorporated in the PP matrix. For example, PP/20A(5 wt %)/PPMA(10 wt %) and PP/30B(5 wt %)/SMA(5 wt %) composites exhibited nanoscaled dispersion of 20A or 3013 in the PP matrix. Differential scanning calorimetry (DSC) results indicated that the organoclays served as nucleation agents for the PP matrix. Generally, their nucleation effectiveness increased with the addition of compatibilizers. The thermal stability enhancement of PP after adding 20A was confirmed with thermogravimetric analysis (TGA). The enhancement became more evident as a suitable compatibilizer was further added. However, for the 30B-included composites, thermal stability enhancement was not evident. The dynamic mechanical properties (i.e., storage modulus and loss modulus) of PP increased as the nanocomposites were formed; the properties increment corresponded to the organoclay dispersion status in the matrix. (C) 2004 Wiley Periodicals, Inc.