This work investigates two different melt-blending strategies for preparing compatibilized polypropylene-clay nanocomposites, specifically: (1) conventional twin-screw extrusion, and (2) single-screw extrusion capable of direct supercritical carbon dioxide (scCO(2)) feed to the extruder barrel. Proportional amounts (3 : 1) of maleic anhydride functionalized polypropylene compatibilizer and organically modified montmorillonite clay at clay loadings of 1, 3, and 5 wt % are melt-blended with a polypropylene homopolymer using the two approaches. The basal spacing, degree of exfoliation, and dispersion of organoclay is assessed using X-ray diffraction, transmission electron microscopy, and rheology. In terms of the latter, both steady shear and small-amplitude oscillatory shear provide information about the apparent yield stress and solid-like terminal behavior respectively. Finally, nanoindentation is performed to determine the room temperature modulus of each melt-blended nanocomposite. The results reveal unequivocally that the high shear of the twin-screw process is vastly superior to the single-screw with in-line scCO(2) addition in generating well-exfoliated, percolated polypropylene-clay nanocomposites. It is likely that increased contact time between clay and scCO(2) is necessary for scCO(2) to positively affect exfoliation. (c) 2006 Wiley Periodicals, Inc.