Effect of selective localization of carbon nanotubes in PA6 dispersed phase of PP/PA6 blends on the morphology evolution with time, part 1: Droplet deformation under simple shear flows

Abstract

The deformation of carbon nanotube (CNT)‐filled PA6 droplets in PP matrix was examined under simple shear flows. The morphology of blends with various CNT contents in PA6 were probed by FE‐SEM. Based on the wetting coefficient calculations and rheological measurements, it was noted that the majority of CNTs were selectively located in the PA6 phase for concentrations up to 2 wt%. TEM micrographs evidenced the results for a sample with 0.5 wt% CNT in PA6. Optical microscopy of the blends during simple shear flows revealed the reduced deformability and breakups for filled‐droplets. Such observations were ascribed to the increased viscosity ratio and gradual formation of an elastic structure within the droplets. Maffetone‐Minale transient droplet deformation model was coupled with a modified capillary number to account for the developed elastic forces. It was shown that the contribution of such forces to the total shape‐conserving forces could arise up to 99% in comparison with the well‐known interfacial forces. These resisting forces can be so strong that for blends with CNT concentrations above 0.5 wt% in PA6 almost no deformation was observed under the applied shear stresses in this work. POLYM. ENG. SCI., 55:1504–1519, 2015. © 2014 Society of Plastics Engineers