Evaluating screw performance: Extrusion process stability and the degree of mixing from melt rheology data and from measurement on an instrumented extruder
TL;DR: In this paper, a comprehensive study of polyethylene extrusion was carried out with an instrumented extruder on several screws differing in geometry and paralleled with capillary rheometry of the extrudate leading to melt viscosity and elasticity functions.
Abstract: A comprehensive study of polyethylene extrusion was carried out with an instrumented extruder on several screws differing in geometry and paralleled with capillary rheometry of the extrudate leading to melt viscosity and elasticity functions. Assuming Oldroyd's constitutive equation for molten polyethylene and the extrudate melt temperature oscillation (ΔTm) as a measure of the process stability and an indication of melt mixing quality, it was found that the product of the dimensionless numbers (Deborah, De and Brinkman, Br) correlates well (r = 0.93) with ΔTm. Since the Br and De groups follow from the rheological characteristics of the melt and the extrusion process parameters, a relationship of type: ΔTm = a + b (De) (Br) appears useful in designing an extrusion process (for a polymer of known rheology) with respect to its stability, and indirectly, its mixing efficiency.
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TL;DR: In this article, a fully predictive computer model was developed for a single-screw plasticating extrusion (with conventional screws) taking into account five zones of the extruder (hopper, solids conveying, delay zone, melting zone, melt conveying) and the die, making it possible to predict a mass flow rate of the polymer.
Abstract: A fully predictive computer model has been developed for a single-screw plasticating extrusion (with conventional screws). The model takes into account five zones of the extruder (hopper, solids conveying, delay zone, melting zone, melt conveying) and the die, and describes an operation of the extruder-die system, making it possible to predict a mass flow rate of the polymer, pressure and temperature profiles along the screw channel and in the die, solid bed profile, and power consumption. Moreover, mixing degree, temperature fluctuation and viscoelastic properties of the polymer are estimated. The simulation parameters are the material and rheological properties of the polymer, the screw, hopper and die geometry, and the operating conditions (screw speed and barrel temperature profile). Such a comprehensive approach to the modeling of extrusion creates the possibility of optimizing the process, for example, from the point of view of the quality of extrusion. The model has been verified experimen...
33 citations
TL;DR: In this article, a fully predictive computer model SSEM (Single-Screw Extrusion Model) was developed for the single-screw plasticating extruders (with conventional and mixing screws), taking into account five zones of the extruder (hopper, solids conveying, delay zone, melting zone, and melt conveying).
Abstract: A fully predictive computer model SSEM (Single-Screw Extrusion Model) has been developed for the single-screw plasticating extruders (with conventional and mixing screws). The model takes into account five zones of the extruder (hopper, solids conveying, delay zone, melting zone, and melt conveying) and the die, and it describes an operation of the extruder-die system, making it possible to predict the mass flow rate of the polymer, the pressure and temperature profiles along the screw channel and in the die, the solid-bed profile, and power consumption. Moreover, the mixing degree, the temperature fluctuation, and the viscoelastic characteristic of the polymer are evaluated. The model also makes it possible to predict the morphological changes of the polymer blend during the compounding process in the single-screw extruder. The simulation parameters are the material and rheological properties of the polymer, the screw, hopper, and die geometry, and the operating conditions (screw speed and barre...
26 citations
TL;DR: In this article, a fully predictive computer model SSEM (single-screw extrusion model) has been developed for the single-crew plasticating extruders (with conventional and non-conventional screws of different geometry, and different dies as well).
19 citations
TL;DR: The ability of a screw to manufacture products of good quality with high productivity and low cost is called its performance At the design stage of an extrusion process, evaluation of screw performance is very important and can be realized on the basis of experimental and theoretical investigations.
Abstract: The ability of a screw to manufacture products of good quality with high productivity and low cost is called its performance At the design stage of an extrusion process, evaluation of screw performance is very important and can be realized on the basis of experimental and theoretical investigations
8 citations
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TL;DR: In this article, the authors proposed a method to predict the distribution of residence-times in large systems using distribution-functions for residence times, which can be used to calculate the efficiencies of reactors and blenders.
1,929 citations
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01 Jan 2006
TL;DR: In this paper, the authors present an overview of the history of the field of polymers in terms of elementary steps and shaping methods, and present and future perspectives of this field.
Abstract: 1 History, Structural Formulation of the Field Through Elementary Steps, and Future Perspectives 11 Historical Notes 12 Current Polymer Processing Practice 13 Analysis of Polymer Processing in Terms of Elementary Steps and Shaping Methods 14 Future Perspectives: From Polymer Processing to Macromolecular Engineering 2 The Balance Equations and Newtonian Fluid Dynamics 21 Introduction 22 The Balance Equations 23 Reynolds Transport Theorem 24 The Macroscopic Mass Balance and the Equation of Continuity 25 The Macroscopic Linear Momentum Balance and the Equation of Motion 26 The Stress Tensor 27 The Rate of Strain Tensor 28 Newtonian Fluids 29 The Macroscopic Energy Balance and the Bernoulli and Thermal Energy Equations 210 Mass Transport in Binary Mixtures and the Diffusion Equation 211 Mathematical Modeling, Common Boundary Conditions, Common Simplifying Assumptions, and the Lubrication Approximation 3 Polymer Rheology and Non-Newtonian Fluid Mechanics 31 Rheological Behavior, Rheometry, and Rheological Material Functions of Polymer Melts 32 Experimental Determination of the Viscosity and Normal Stress Difference Coefficients 33 Polymer Melt Constitutive Equations Based on Continuum Mechanics 34 Polymer Melt Constitutive Equations Based on Molecular Theories 4 The Handling and Transporting of Polymer Particulate Solids 41 Some Unique Properties of Particulate Solids 42 Agglomeration 43 Pressure Distribution in Bins and Hoppers 44 Flow and Flow Instabilities in Hoppers 45 Compaction 46 Flow in Closed Conduits 47 Mechanical Displacement Flow 48 Steady Mechanical Displacement Flow Aided by Drag 49 Steady Drag-induced Flow in Straight Channels 410 The Discrete Element Method 5 Melting 51 Classification and Discussion of Melting Mechanisms 52 Geometry, Boundary Conditions, and Physical Properties in Melting 53 Conduction Melting without Melt Removal 54 Moving Heat Sources 55 Sintering 56 Conduction Melting with Forced Melt Removal 57 Drag-induced Melt Removal 58 Pressure-induced Melt Removal 59 Deformation Melting 6 Pressurization and Pumping 61 Classification of Pressurization Methods 62 Synthesis of Pumping Machines from Basic Principles 63 The Single Screw Extruder Pump 64 Knife and Roll Coating, Calenders, and Roll Mills 65 The Normal Stress Pump 66 The Co-rotating Disk Pump 67 Positive Displacement Pumps 68 Twin Screw Extruder Pumps 7 Mixing 71 Basic Concepts and Mixing Mechanisms 72 Mixing Equipment and Operations of Multicomponent and Multiphase Systems 73 Distribution Functions 74 Characterization of Mixtures 75 Computational Analysis 8 Devolatilization 81 Introduction 82 Devolatilization Equipment 83 Devolatilization Mechanisms 84 Thermodynamic Considerations of Devolatilization 85 Diffusivity of Low Molecular Weight Components in Molten Polymers 86 Boiling Phenomena: Nucleation 87 Boiling-Foaming Mechanisms of Polymeric Melts 88 Ultrasound-enhanced Devolatilization 89 Bubble Growth 810 Bubble Dynamics and Mass Transfer in Shear Flow 811 Scanning Electron Microscopy Studies of Polymer Melt Devolatilization 9 Single Rotor Machines 91 Modeling of Processing Machines Using Elementary Steps 92 The Single Screw Melt Extrusion Process 93 The Single Screw Plasticating Extrusion Process 94 The Co-rotating Disk Plasticating Processor 10 Twin Screw and Twin Rotor Processing Equipment 101 Types of Twin Screw and Twin Rotor-based Machines 102 Counterrotating Twin Screw and Twin Rotor Machines 103 Co-rotating, Fully Intermeshing Twin Screw Extruders 11 Reactive Polymer Processing and Compounding 111 Classes of Polymer Chain Modification Reactions, Carried out in Reactive Polymer Processing Equipment 112 Reactor Classification 113 Mixing Considerations in Multicomponent Miscible Reactive Polymer Processing Systems 114 Reactive Processing of Multicomponent Immiscible and Compatibilized Immiscible Polymer Systems 115 Polymer Compounding 12 Die Forming 121 Capillary Flow 122 Elastic Effects in Capillary Flows 123 Sheet Forming and Film Casting 124 Tube, Blown Film, and Parison Forming 125 Wire Coating 126 Profile Extrusion 13 Molding 131 Injection Molding 132 Reactive Injection Molding 133 Compression Molding 14 Stretch Shaping 141 Fiber Spinning 142 Film Blowing 143 Blow Molding 15 Calendering 151 The Calendering Process 152 Mathematical Modeling of Calendering 153 Analysis of Calendering Using FEM Appendix A: Rheological and Thermophysical Properties of Polymers Appendix B: Conversion Tables to the International System of Units (SI) Appendix C: Notation Author Index Subject Index
1,163 citations
TL;DR: In this paper, a new constitutive equation was proposed to predict the behavior of nonpolar solutions and polymeric melts and that it may work well on polar systems in the range of high deformation rates.
Abstract: The importance and characteristics of viscoelastic fluid behavior are briefly reviewed, as are theoretical predictions of the relationships between the stresses developed in such a fluid and its deformation rate and history. It is seen that most of the equations available for the prediction of these stresses(variously termed “constitutive equations” or “rheological equations of state”) either do not predict the properties of real materials correctly or, alternately, are of such overriding complexity that they cannot be applied to the solution of any but the simplest real problems. A new constitutive equation in which all the significant parameters may be evaluated from only two sets of experiments is developed. Comparison with available experimental results, while not entirely conclusive, indicates that the equation may predict correctly the behavior of nonpolar solutions and polymeric melts and that it may work well on polar systems in the range of high deformation rates, i.e., the region of primary industrial interest. Several problems of interest to the plastics industry are worked to illustrate the use of this constitutive equation.
221 citations
TL;DR: In this article, the authors considered the mixing of liquids of high viscosity using a continuous deformation and showed the advantage of using matrix methods in considering certain types of distribution problems.
179 citations