The influence of shear flow on the crystallization of polyamide 6/MMT nanocomposites prepared by melt intercalation process was investigated in detail by differential scanning calorimetry. The melted nanocomposites were controlled sheared in the steady and oscillatory shear flow, using a rotational rheometer, and cooled in an inert atmosphere. The effects of shear rate or frequency, clay concentration, and crystallization conditions on PA 6 crystalline phase development were studied. As expected, an opposite impact of shearing on gamma-phase formation in the nanocomposites and neat matrix was found. Surprisingly, a critical shear frequency for the onset of gamma-form crystallinity formation in the nanocomposites, increasing with the filler content as a consequence of polymer chains confinement within oriented clay platelets was found. At higher shear frequencies, the proportion of gamma-form in the nano-composites increased dramatically with the clay concentration and reached 30-40%. The shear flow effects were influenced by cooling conditions, and more significant effect for rapidly cooled samples was observed. The isothermal crystallization at the solidification temperature 205 degrees C reduced the gamma-form content. (c) 2007 Wiley Periodicals, Inc.