Viscoelastic Properties and Morphology of Two‐Phase Polypropylene/Polyamide 6 Blends in the Melt. Interpretation of Results with an Emulsion Model

Abstract

Linear viscoelastic dynamic moduli of two‐phase PP/PA6 blends in the molten state have been measured as a function of frequency in a cone and plate rheometer. With respect to the PP and PA6 components, blends are characterized by high values of the storage modulus at low frequencies and long relaxation times. A parallel has been drawn between these results and morphological observations of sheared specimens showing that the time required for deformed dispersed domains to revert to their spherical shape is of the same order of magnitude as mechanical relaxation times. A model for undiluted emulsions of Newtonian liquids has been used to account for the variations of dynamic moduli in the terminal zone. In this frequency range, the rheological behavior is directly related to a few physically significant parameters such as zero‐shear viscosity of phases, dispersed particle size, and surface tension between phases.