Characterizing the flow of slurries using percolation theory‐based functions

Wetzel, Mark D.; Campbell, Gregory A.

doi:10.1002/pen.24435

Cited by 6 publications

(7 citation statements)

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“…A set of constitutive models were developed to predict fluid viscosity for filled systems, including high loadings of particulate solids based rheological measurements. [24,25,[27][28][29][30] This investigation focuses on mono-dispersed particle size and mono-dispersed initial agglomerate size. However, the authors have found that PSD does affect the power law and thus the effect to total filler concentration on the shear stress.…”

Section: Rupture Erosionmentioning

confidence: 99%

“…A filler percolation model [33] was used to fit to capillary rheometer data. [24,25,30] The Campbell-Forgacs model and a proposed modified addition have the form:…”

Section: Rupture Erosionmentioning

confidence: 99%

“…An alternative approach is proposed where the function for β is related to non-dissipating structures formed in filled systems. [24,25,[27][28][29][30] The non-dissipating volume fraction, V frac , of the filled flowing fluid was found to be statistically related to the power law, n, and is written as…”

Section: Cohesive Force F C and Thermodynamic Interactions Affecting...mentioning

confidence: 99%

“…Calculate the cohesive force, F c , using the agglomerate structure and the particle-particle interaction forces with Hamaker's approach. Particle packing arrangement and density are incorporated in the cohesive force calculations using Equations (30)…”

Section: Calculate the Component Materials Hamaker Constantsmentioning

confidence: 99%

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Modeling the thermodynamics and kinematics of spherical particle dispersion in polymer melts: Model derivation and simulation analysis

Wetzel¹,

Campbell

2022

Polymer Engineering & Sci

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A cohesive binding-force-based model has been developed to predict solid particulate agglomerate break up in fluids sheared volumes leading to particle dispersion in polymer melt extrusion processes. Particle-particle, particlepolymer, and particle-modifier-polymer interactions are modeled using adaptions from Hamaker's approach. This leads to an analytical molecular attraction approach that captures the effects of: (1) particle-particle agglomerate cohesion based on material properties and structure, (2) the effect of surface modifiers on cohesive strength and particle separation, (3) polymer wetting and melt adhesion leading to medium-agglomerate stress transfer, (4) applied fluid mechanical stress and melt temperature, and (5) residence time. In this paper, the model is evaluated, and several predicted effects of processing parameters on reduction of agglomerate size are calculated and graphically presented from this phase of the research. The predicted trends are consistent with the published data in the literature.

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Section: Rupture Erosionmentioning

confidence: 99%

“…A filler percolation model [33] was used to fit to capillary rheometer data. [24,25,30] The Campbell-Forgacs model and a proposed modified addition have the form:…”

Section: Rupture Erosionmentioning

confidence: 99%

Section: Cohesive Force F C and Thermodynamic Interactions Affecting...mentioning

confidence: 99%

Section: Calculate the Component Materials Hamaker Constantsmentioning

confidence: 99%

See 2 more Smart Citations

Modeling the thermodynamics and kinematics of spherical particle dispersion in polymer melts: Model derivation and simulation analysis

Wetzel¹,

Campbell

2022

Polymer Engineering & Sci

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“…These results led to an investigation of how this dissipation mechanism proposal would be used to interpret the development of the power law in a filled polymer system [9,10]. The initial system used was a low density polyethylene filled with TiO2 incrementally up to 0.495 volume fraction.…”

Section: Application Of Theory To a Filled Polymersmentioning

confidence: 99%

Investigation of the Effect of Filler Concentration on the Flow Characteristics of Filled Polyethylene Melts

Campbell

Wetzel²

2018

International Polymer Processing

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All polymer slurries that have a high concentration of filler are shear thinning. Shear thinning is an important characteristic of polymers, filled and unfilled, because it leads to being able to increase the throughput, shear rate in a die or mold without having to use substantially more power to increase the flow rate. With a perfect pseudoplastic fluid, n = 0, there would be no increase in energy as the flow rate is increased. This is of course not allowed by the second law of thermodynamics. Newtonian fluid based slurries show an increase in shear thinning as the concentration of "filler" increases above the percolation threshold. As the maximum packing factor is approached they approach a perfect pseudoplastic fluid. At times the shear thinning characteristics of a filled polymer does not increase substantially as the filler is increased in the same manner as the Newtonian fluid based slurry. Therefore, it is important to investigate the physics that controls shear thinning so that flow in extrusion and injection flow models can be more predictive when dealing with filled polymer systems.

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A new 2.5‐D twin screw extruder melting model with comparisons to data

Campbell,

Wetzel,

Andersen

et al. 2023

Polymer Engineering & Sci

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Many polymers are processed and compounded in co‐rotating, fully intermeshing twin screw extruders. A typical compounding process consists of multiple unit operations including feed introduction, solids transport, transitioning from the conveying zone to the kneading block melting zone, melting, a downstream feed zone, a mixing zone, a devolatilization region, and a pressure generating discharge section. This paper will focus on the kneading block melting zone which typically includes a reverse pitch element so the kneaders remain full. Mechanisms for flow and energy input to pellets in kneading elements, including friction heating, pellet compression, energy diffusion, and viscous dissipation to form a melt phase: followed by viscous dissipation in a solid pellet/melt slurry, and heat transfer; are developed and implemented in a novel melting model. The model is validated with extrusion measurements and visualizations using low density polyethylene (LDPE). The predictions of the model are also compared with a classical set of experiments using high density polyethylene (HDPE). This paper describes the physics and engineering concepts that the authors feel are inherent in the melting section of the twin screw extruder where a large pressure peak is calculated using the friction and compression of the polymer pellets. The modeled increase in pellet bulk/surface temperature is due to the inclusion of four energy sources, pellet compression, thermal diffusion, friction energy dissipation, and viscous energy dissipation. This combined thermal dynamics based melting model results in a novel melting protocol. The melting mechanisms are coupled to flow regimes in the kneading blocks as melting progresses. The effects of throughput, Q, and screw rotation speed, N, are also examined.Highlights Novel 2.5D melting model for corotating, intermeshing twin‐screw extruders. Energy for melting; friction, deformation, diffusion, and viscous dissipation. The model helps elucidate mechanisms during melting in a twin‐screw extruder.

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Characterizing the flow of slurries using percolation theory‐based functions

Cited by 6 publications

References 58 publications

Modeling the thermodynamics and kinematics of spherical particle dispersion in polymer melts: Model derivation and simulation analysis

Modeling the thermodynamics and kinematics of spherical particle dispersion in polymer melts: Model derivation and simulation analysis

Investigation of the Effect of Filler Concentration on the Flow Characteristics of Filled Polyethylene Melts

A new 2.5‐D twin screw extruder melting model with comparisons to data

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