Working Paper Article Version 1 This version is not peer-reviewed

Dispersion of Graphite Nanoplates in Polypropylene by Melt Mixing: The Effect of Hydrodynamic Stresses and Residence Time

Version 1 : Received: 30 November 2020 / Approved: 1 December 2020 / Online: 1 December 2020 (18:25:01 CET)

A peer-reviewed article of this Preprint also exists.

Ferrás, L.L.; Fernandes, C.; Semyonov, D.; Nóbrega, J.M.; Covas, J.A. Dispersion of Graphite Nanoplates in Polypropylene by Melt Mixing: The Effects of Hydrodynamic Stresses and Residence Time. Polymers 2021, 13, 102. Ferrás, L.L.; Fernandes, C.; Semyonov, D.; Nóbrega, J.M.; Covas, J.A. Dispersion of Graphite Nanoplates in Polypropylene by Melt Mixing: The Effects of Hydrodynamic Stresses and Residence Time. Polymers 2021, 13, 102.

Journal reference: Polymers 2020, 13, 102
DOI: 10.3390/polym13010102

Abstract

Melt mixing is a convenient method to prepare polymer nanocomposites, but the extent of the dispersion of the solid filler reached is often limited, and may compromise the anticipated performance of these materials during service. Since the efficiency of extensional flows on dispersion is now well recognized, several mixers were designed with the aim of inducing both shear and extensional flow components. This work combines experimental and numerical data to better understand the kinetics of the dispersion of graphite nanoplates in a polypropylene melt, using a mixing device that consists of a series of stacked rings with equal outer diameter and alternating larger and smaller inner diameters, thus creating a series of converging/diverging flows. Numerical simulation of the flow using the opensource OpenFOAM software assuming both inelastic and viscoelastic responses predicted the velocity, streamlines, flow type and shear and normal stress fields for the mixer. Experimental and computed data were combined to determine the trade-off between the local degree of dispersion of the PP/GnP nanocomposite, measured as Area ratio, and the absolute average value of the hydrodynamic stresses multiplied by the local cumulative residence time. From considerations based on a theoretical approach to dispersion, the cohesive strength of the GnP agglomerates studied was estimated to be in the range 3 - 10kPa.

Subject Areas

Polymer Nanocomposites; Nanofiller Dispersion; Flow-Cells; Experimental and Numerical; Viscoelastic Fluids

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