Dynamics of Filler Size and Spatial Distribution in a Plasticating Single Screw Extruder – Modeling and Experimental Observations

Abstract

A model of agglomerate break-up, incorporating both rupture and erosion, is employed to predict the dynamics of filler size distribution in a plasticating single screw extruder. Filler spatial distribution along the extruder length was also ascertained and direct comparison of experimental and computational data proved to be satisfactory. The method was also used to investigate the effect of material properties, operating conditions and extruder geometry on the dynamics of agglomerate dispersion along a single screw extruder. Generally, dispersion levels were primarily governed by the magnitude of the hydrodynamic stresses developed in the extruder and the residence time in the melt.

In-Line Rheo-Optical Investigation of the Dispersion of Organoclay in a Polymer Matrix during Twin-Screw Compounding

“…It has been postulated that break-up of particle agglomerates is associated with the development of sufficiently high stresses, this being a relatively fast process, whereas erosion can develop under lower stresses, but requires longer times [ 44 , 45 , 46 ]. The prevalence of each dispersion route can be predicted based on the magnitude of the fragmentation number Fa , which compares the hydrodynamic stress σ with the cohesive strength σ c of primary particles [ 44 , 45 , 47 ].…”

“…It has been postulated that break-up of particle agglomerates is associated wi development of sufficiently high stresses, this being a relatively fast process, wherea sion can develop under lower stresses, but requires longer times [44][45][46]. The preva of each dispersion route can be predicted based on the magnitude of the fragmen number Fa, which compares the hydrodynamic stress σ with the cohesive strength primary particles [44,45,47]. Thus, the in-process rheo-optical characterization of cla persion in PDMS presented in Figures 4 and 5 seems to indicate that larger screw s A satisfactory match between the computed and measured shear viscosities is observed in Figure 6 for the CPNC processed with a screw speed of 80 rpm within the whole range of shear rates, whereas a discrepancy between the computed and measured values at lower shear rates is evident for the CPNC processed at 20 rpm.…”

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

“…A model for solid agglomerate dispersion in single-screw extruders was developed by Domingues et al [ 21 ], combining numerical simulations of flow patterns in the metering section of the screw with a Monte Carlo method of cluster rupture and erosion assessed by a local fragmentation number. The model was applied successfully to predict the dispersion of micronized silica in a high-density polyethylene melt [ 22 ]. Berzin et al [ 23 ] proposed a model of agglomeration/breakup of inorganic fillers to predict dispersion in a polymer matrix along a co-rotating twin-screw extruder as a function of the screw geometry and processing conditions.…”

Effects of Particle Size and Surface Chemistry on the Dispersion of Graphite Nanoplates in Polypropylene Composites

“…The rate of A r evolution along the equipment varies with GnP type, as perceived from the linear slopes indicated in Figure 6. These observations may be analyzed in light of the rupture and erosion dispersion mechanisms of agglomerated particles in melts postulated by Manas-Zloczower and co-workers [40,41]. These authors postulated that the route to dispersion depends on the magnitude of a fragmentation number, F a , and on the on the probability for break-up, P break .…”