Modeling devolatilization in single- and multi-screw extruders

Marschik, Christian; Löw-Baselli, Bernhard; Miethlinger, Jürgen

doi:10.1063/1.5016746

Cited by 11 publications

(23 citation statements)

References 11 publications

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“…Removal of such volatiles minimizes hydrolysis, acidolysis, and improves polymer melt odor to increase the value of recyclate. [ 33,34,35 ] Polymer melts can also be filtered to remove larger, non‐volatile, contaminants such as dust or gel particles and improve blend homogeneity, mechanical and optical properties. [ 33,36,37 ] Melt filters are chosen according to specific extrusion contamination and can include screen‐changers such as slide plates, woven screens, or filter cartridges.…”

Section: Introductionmentioning

confidence: 99%

Mechanical Recycling of Packaging Plastics: A Review

Schyns

Shaver

2020

Macromol. Rapid Commun.

796

692

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The current global plastics economy is highly linear, with the exceptional performance and low carbon footprint of polymeric materials at odds with dramatic increases in plastic waste. Transitioning to a circular economy that retains plastic in its highest value condition is essential to reduce environmental impacts, promoting reduction, reuse, and recycling. Mechanical recycling is an essential tool in an environmentally and economically sustainable economy of plastics, but current mechanical recycling processes are limited by cost, degradation of mechanical properties, and inconsistent quality products. This review covers the current methods and challenges for the mechanical recycling of the five main packaging plastics: poly(ethylene terephthalate), polyethylene, polypropylene, polystyrene, and poly(vinyl chloride) through the lens of a circular economy. Their reprocessing induced degradation mechanisms are introduced and strategies to improve their recycling are discussed. Additionally, this review briefly examines approaches to improve polymer blending in mixed plastic waste streams and applications of lower quality recyclate.

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Section: Introductionmentioning

confidence: 99%

Mechanical Recycling of Packaging Plastics: A Review

Schyns

Shaver

2020

Macromol. Rapid Commun.

796

692

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“…Sub-functions a 00 -a 16 Constants b 00 -b 12 Constants c 00 -c 21 Constants Definitions of A x , m x , and p x : the coefficients for the finite difference matrix, the vector with the unknown velocities including the cross-channel pressure gradient, and the load vector in the cross-channel direction, respectively. Note that the indices i and j run from 1 .…”

Section: Discussionmentioning

confidence: 99%

“…Pachner et al presented a generalized two‐dimensional output model that is valid across the full application range of polymer melts and for both positive and negative dimensionless pressure gradients, that is, for both pressure build‐up and overridden zones. Marschik et al presented a three‐dimensional output model for smooth‐bore single screw‐extruders as well as for smooth‐ and grooved‐feed extruders, additionally taking into account the effect of the flight flanks on the flow rate. A heuristic approximation equation was developed for predicting the dimensionless throughput depending on the dimensionless pressure gradient, the power‐law exponent, the screw‐pitch ratio, and the channel‐height to channel‐width ratio.…”

Section: Introductionmentioning

confidence: 99%

“…A heuristic approximation equation was developed for predicting the dimensionless throughput depending on the dimensionless pressure gradient, the power‐law exponent, the screw‐pitch ratio, and the channel‐height to channel‐width ratio. The novelty of the last sources cited lies in the generation of an analytical relationship using symbolic regression based on genetic programming. Koza was the first who investigated this method in detail in 1992.…”

Section: Introductionmentioning

confidence: 99%

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Heuristic analysis of viscous dissipation in single‐screw extrusion

Roland

Miethlinger

2018

Polymer Engineering & Sci

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Modeling the non-Newtonian flow of polymer melts in single-screw extrusion generally requires numerical methods. This study analyzes the viscous dissipation of the melt-conveying zone, which is mainly responsible for the axial melt temperature increase, in single-screw extruders for both one-and two-dimensional stationary, fully developed flows of a power-law fluid. Rewriting the flow equations and applying the theory of similarity revealed three independent parameters that influence the physics of the fluid flow: the dimensionless pressure gradient P p;z , the power-law exponent n, and the screw-pitch ratio t=D b . Based on these parameters, we carried out a comprehensive numerical parametric study evaluating viscous dissipation and flow rate. Here, we present four heuristic models that predict the viscous dissipation of a powerlaw fluid in the melt-conveying zone of single-screw extruders. For one-dimensional and two-dimensional flows, we developed models for both a given pressure gradient and a given throughput. The approximation equations obtained allow fast and stable prediction without the need for numerical simulations of viscous dissipation. The accuracy of the heuristic models developed was validated in an error analysis, which showed that our approaches provide excellent approximations of the numerical results.

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“…Similar to the previous approach, the range of the dimensionless down-channel pressure gradients was adjusted as a function of the power-law index. The validity of the two- and three-dimensional melt-conveying models was tested against experimental extrusion data measured for both standard and high-performance screws [ 140 , 141 , 142 ]. Recently, the usefulness of the symbolic regression analysis was analyzed in a comparative study that investigated various data-based modeling approaches [ 143 ].…”

Section: Approximate Methodsmentioning

confidence: 99%

Melt Conveying in Single-Screw Extruders: Modeling and Simulation

Marschik¹,

Roland

Osswald

2022

Polymers

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Numerous analyses have modeled the flow of polymer melts in the melt-conveying zones of single-screw extruders. While initial studies mainly provided exact analytical results for combined drag and pressure flows of Newtonian fluids, more recently developed, numerical methods seek to deepen the understanding of more realistic flow situations that include shear-thinning and non-isothermal effects. With the advent of more powerful computers, considerable progress has been made in the modeling and simulation of polymer melt flows in single-screw extruders. This work reviews the historical developments from a methodological point of view, including (1) exact analytical, (2) numerical, and (3) approximate methods. Special attention is paid to the mathematical models used in each case, including both governing flow equations and boundary conditions. In addition, the literature on leakage flow and curved-channel systems is revisited.

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Modeling devolatilization in single- and multi-screw extruders

Cited by 11 publications

References 11 publications

Mechanical Recycling of Packaging Plastics: A Review

Mechanical Recycling of Packaging Plastics: A Review

Heuristic analysis of viscous dissipation in single‐screw extrusion

Melt Conveying in Single-Screw Extruders: Modeling and Simulation

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