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. FIG. 9. Optical micrographs of droplet deformation with time in PP/PA6 sample at a shear-rate of 2 s 21 . The micrographs are captured after startup of shear flow at (a) 0 s, (b) 1 s, (c) 2 s, (d) 5 s, (e) 10 s, (g) 20 s, (h) 50 s, and (k) 120 s. The arrow in (k) indicates the applied flow direction for all micrographs. FIG. 10. Optical micrographs of droplet deformation with time in PP/PA6-0.1 sample at a shear-rate of 2 s 21 . The micrographs are captured after startup of shear flow at (a) 0 s, (b) 1 s, (c) 2 s, (d) 5 s, (e) 10 s, (g) 20 s, (h) 50 s, and (k) 120 s. The arrow in (k) indicates the applied flow direction for all micrographs.

Effect of Organo‐Modified Montmorillonite on the Morphology and Properties of SEBS/TPU Nanocomposites

“…To ascertain the possible mechanism of the morphology refinement in SEBS/TPU/OMMT nanocomposites, the location of OMMT nanoparticles has to be determined. In general, the final location of OMMT nanoparticles depends on thermodynamic and kinetics aspects, and therefore, previous studies have reported the use of classical thermodynamic methods to predict the distribution of nanoparticles in immiscible blends , and the wetting coefficient ω is defined as follows: where γ organoclay ‐ SEBS , γ organoclay ‐ TPU , and γ SEBS ‐ TPU are the interfacial energies between organoclay/SEBS, organoclay/TPU, and SEBS/TPU, respectively. If the calculated ω > 1, the organoclay would be preferentially located in the TPU phase; if ω < −1, the organoclay will be embedded in the SEBS phase, for −1 < ω < 1, the clays are estimated to be dispersed at the phase interface.…”

Effect of selective localization of carbon nanotubes in pa6 dispersed phase of PP/PA6 blends on the morphology evolution with time, part 2: Relaxation of deformed droplets after cessation of flow

“…The materials and methods are fully described in the first part of this work . Here, a brief overview is provided.…”

“…The incorporation of a third component such as nanoparticles should of course affect these factors and therefore the final morphology. In the first part of this work on PP/PA6‐carbon nanotube (CNT) blends , it was evidenced by several methods that the selective localization of CNTs in the PA6 dispersed phase changed the deformability of droplets under simple shear flows. By the utilization of a shear‐optical microscope, online investigation of morphology evolutions under flow was performed with time.…”

“…The capillary number was accordingly modified to account for such forces. The effects of CNT inclusions on the evolutions of the morphology were so strong that for highly filled droplets almost no deformation was observed under the applied shear‐rates .…”

Cellulose monoacetate/polycaprolactone and cellulose monoacetate/polycaprolactam blended nanofibers for protease immobilization

“…reported the immobilization of 3‐hydroxybenzoate‐6‐hydroxylase on electrospun PCL ultrafine fibers for potential applications for heterogeneous catalysts. PA6 is a semicrystalline polymer with good tensile properties, and it has been used for textiles, adhesives, and biomedical purposes . PA6/chitosan nanofibers were used as support to immobilize Trametes versicolor laccase for the elimination of endocrine‐disrupting chemicals .…”