VISCOELASTIC BEHAVIOR OF POLYAMIDE-6 MELTS

The rheological behaviour of nylon 6 melts of different molecular weights was investigated by means of capillary viscometers, a modified Weissenberg rheogoniometer, a sandwich creep apparatus, and an oscillatory viscometer. The influence of moisture content and residence time on the stability behaviour of the melts is demonstrated by measurements. Due to the comparable Schulz-Flory molecular weight distributions of the melts a mastercurve for the viscosity functions can be constructed by normalizing the viscosity and the shear rate by means of the zeroshear viscosity. The mastercurve is not only temperature invariant but also independent of the molecular weight. Temperature and molecular weight invariant plots are also obtained for the extrudate swell and entrance pressure losses as functions of the wall shear stress. Coincident values for the steady-state compliance are determined from oscillatory measurements, the recoverable shear strains, and the primary normal stress differences in the linear range of shear flow. As a consequence of the constant ratio {Mathematical expression} the steady-state compliance is independent of the molecular weight. The temperature dependence of the zeroshear viscosity follows an Arrhenius relation with a constant activation energy of E0 = 60 kJ/Mol. © 1979 Dr. Dietrich Steinkopff Verlag.