A newly designed mixer, the Alberta polymer asymmetric minimixer (APAM), was compared to the MiniMAX molder with flow simulation and flow visualization techniques to evaluate the performance of the mixers. The APAM has a unique, asymmetric design consisting of a varying clearance between the rotor blade tips and the cup wall, which enables the material to be squeezed, stretched, and kneaded in high-shear and converging zones. Flow simulation showed that substantial folding and axial movement occurred in this mixer and that the pressure and velocity profiles exhibited high values at the rotor tip with the smallest rotor tip/cup clearance. In contrast, the MiniMAX molder had very simple flow patterns, which were insufficient to induce good dispersive and distributive mixing. These results concurred with those from an earlier work that studied the structure of blends and nanocomposites processed in the APAM compared to other polymer processing equipment. © 2005 Wiley Periodicals, Inc.