This article describes the synthesis of poly(omega-lauryl lactam) by a reactive extrusion process. Anionic ring-opening polymerization was performed in an intermeshing corotating twin-screw extruder. We investigated the evolution of conversion of w-lauryl lactam as a function of reaction time, screw speeds, different feed rates, and different screw configurations along the screw axis in a twin-screw extruder. For comparison with continuous polymerization in a twin-screw extruder, we studied polymerization in an internal mixer, which was considered a batch reactor. We found the final conversion of w-lauryl lactam made in a twin-screw extruder was higher than in an internal mixer. Higher molecular weights are found at lower screw speeds and feed rates. Melt viscosities and mechanical properties of the polymers were measured. Residence time, molecular weights, and shear mixing have the main effect on the mechanical properties of products. The twin-screw extruder performance was interpreted in terms of commercial software. It was found that twin-screw extruder reaction rate was higher than those in the batch reactor and increased locally with screw speed and feed rate. (c) 2005 Wiley Periodicals, Inc.