Shear flow effect on the crystalline forms in polyamide 6/montmorillonite nanocomposites

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 γ‐phase formation in the nanocomposites and neat matrix was found. Surprisingly, a critical shear frequency for the onset of γ‐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 γ‐form in the nanocomposites 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°C reduced the γ‐form content.