In this study, polymer nanocomposites (PNCs) based on polypropylene (PP), organoclay (used as nanoclay), and compatibilizer were prepared by a masterbatch (MB or two-step) as well as by a one-step process. These compounds were then injection molded into tensile test specimens and rectangular plates using conically and hyperbolically shaped nozzles. The use of these nozzles in the injection unit was to enhance intercalation and exfoliation in the PNCs by means of elongational flow. The pressure loss and temperature rise in the compound induced by this flow were characterized in temperature and pressure measurements. An additional calculation using a new analytic model showed good correlation with the measured values for the conically shaped nozzles whereas the pressure drops in the hyperbolically shaped nozzles were underpredicted. Mechanical as well as rheological characterizations were performed on the produced test specimens. The compounds from the MB process showed good intercalation and exfoliation and improved mechanical properties without any special elongational flow treatment. Similar properties were achieved with the one-step process and elongational treatment using a short hyperbolically or conically shaped nozzle. These results indicated that it was possible to eliminate one complete compounding step and achieve the same mechanical properties in polypropylene nanocomposites when elongational elements were used. (c) 2016 Society of Plastics Engineers