Analyzing and Troubleshooting Single-Screw Extruders

Name: Analyzing and Troubleshooting Single-Screw Extruders
Brand: Hanser Publications
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Gregory A. Campbell Mark A. Spalding(Author)

Hanser Publications (Publisher)

2nd Edition

Published on 7. December 2020

864 pages

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978-1-56990-785-6 (ISBN)

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Content

Intro
Contents
Preface
Acknowledgements
1 Single-Screw Extrusion: Introduction and Troubleshooting
1.1 Organization of this Book
1.2 Troubleshooting Extrusion Processes
1.2.1 The Injection Molding Problem at Saturn
1.3 Introduction to Screw Geometry
1.3.1 Screw Geometric Quantitative Characteristics
1.4 Simple Flow Equations for the Metering Section
1.5 Example Calculations
1.5.1 Example 1: Calculation of Rotational and Pressure Flow Components
1.5.2 Example 2: Flow Calculations for a Properly Operating Extruder
1.5.3 Example 3: Flow Calculations for an Improperly Operating Extruder
1.5.4 Metering Channel Calculation Summary
Nomenclature
References
2 Polymer Materials
2.1 Introduction and History
2.1.1 History of Natural Polymers
2.1.2 The History of Synthetic Polymers
2.2 Characteristics of Synthetic Polymers
2.3 Structure Effects on Properties
2.3.1 Stereochemistry
2.3.2 Melting and Glass Transition Temperatures
2.3.3 Crystallinity
2.4 Polymer Production and Reaction Engineering
2.4.1 Condensation Reactions
2.4.2 Addition Reactions
2.5 Polymer Degradation
2.5.1 Ceiling Temperature
2.5.2 Degradation of Vinyl Polymers
2.5.3 Degradation of Condensation Polymers
References
3 Introduction to Polymer Rheology for Extrusion
3.1 Introduction to the Deformation of Materials
3.2 Introduction to Basic Concepts of Molecular Size
3.2.1 Size Distribution Example
3.2.2 Molecular Weight Distributions for Polymers
3.3 Basic Rheology Concepts
3.4 Polymer Solution Viscosity and Polymer Molecular Weight
3.4.1 Sample Calculation of Solution Viscosity
3.5 Introduction to Viscoelasticity
3.6 Measurement of Polymer Viscosity
3.6.1 Capillary Rheometers
3.6.2 Cone and Plate Rheometers
3.6.3 Melt Index and Melt Flow Rate
3.7 Viscosity of Polymers as Functions of Molecular Character, Temperature, and Pressure
3.8 Historical Models for Non-Newtonian Flow
3.9 Power Law and Viscosity Shear Rate Dependence
3.9.1 Shear Stress from Newtonian to Infinite Shear
3.9.2 Viscosity as a Function of Shear Rate
3.9.3 The Power Law and Process Dissipation
3.9.4 Viscosity, Shear Rate, and Dissipation
3.9.5 Percolation in Structured Systems
3.9.6 Tube Flow Data and Data Analysis
3.9.7 Dispersion Based Power Law Constant n
3.9.8 Rheological Implictions for Extrusion and Molding Processes
Nomenclature
References
4 Resin Physical Properties Related to Processing
4.1 Bulk Density and Compaction
4.1.1 Measurement of Bulk Density
4.1.2 Measuring the Compaction Characteristics of a Resin
4.2 Lateral Stress Ratio
4.2.1 Measuring the Lateral Stress Ratio
4.3 Stress at a Sliding Interface
4.3.1 The Screw Simulator and the Measurement of the Stress at the Interface
4.4 Melting Flux
4.5 Heat Capacity
4.6 Thermal Conductivity and Heat Transfer
4.7 Melt Density
Nomenclature
References
5 Solids Conveying
5.1 Description of the Solids Conveying Process
5.2 Literature Review of Smooth-Bore Solids Conveying Models
5.2.1 Darnell and Mol Model
5.2.2 Tadmor and Klein Model
5.2.3 Clarkson University Models
5.2.4 Hyun and Spalding Model
5.2.5 Moysey and Thompson Model
5.3 Modern Experimental Solids Conveying Devices
5.3.1 Solids Conveying Devices at Clarkson University
5.3.2 The Solids Conveying Device at Dow
5.4 Comparison of the Modified Campbell-Dontula Model with Experimental Data
5.4.1 Solids Conveying Example Calculation
5.5 Grooved Bore Solids Conveying
5.5.1 Grooved Barrel Solids Conveying Models
5.6 Solids Conveying Notes
Nomenclature
References
6 The Melting Process
6.1 Compression Ratio and Compression Rate
6.2 The Melting Process
6.2.1 The Melting Process as a Function of Screw Geometry
6.2.2 Review of the Classical Literature
6.2.3 Reevaluation of the Tadmor and Klein Melting Data
6.3 Theory Development for Melting Using Screw Rotation Physics
6.3.1 Melting Model for a Conventional Transition Section Using Screw Rotation Physics
6.3.2 Melting Models for Barrier Screw Sections
6.4 Effect of Pressure on Melting Rate
6.5 One-Dimensional Melting
6.5.1 One-Dimensional Melting Model
6.6 Solid Bed Breakup
6.7 Melting Section Characteristics
Nomenclature
References
7 Fluid Flow in Metering Channels
7.1 Introduction to the Reference Frame
7.2 Laboratory Observations
7.3 Literature Survey
7.4 Development of Linearized Flow Analysis
7.4.1 Example Flow Calculation
7.5 Numerical Flow Evaluation
7.5.1 Simulation of a 500 mm Diameter Melt-Fed Extruder
7.5.2 Extrusion Variables and Errors
7.5.3 Corrections to Rotational Flow
7.5.4 Simulation of the 500 mm Diameter Extruder Using Fc
7.6 Frame Dependent Variables
7.6.1 Example Calculation of Energy Dissipation
7.7 Viscous Energy Dissipation and Temperature of the Resin in the Channel
7.7.1 Energy Dissipation and Channel Temperature for Screw Rotation
7.7.2 Energy Dissipation and Channel Temperature for Barrel Rotation
7.7.3 Temperature Increase Calculation Example for a Screw Pump
7.7.4 Heat Transfer Coefficients
7.7.5 Temperature Calculation Using a Control Volume Technique
7.7.6 Numerical Comparison of Temperatures for Screw and Barrel Rotations
7.8 Metering Section Characteristics
Nomenclature
References
8 Mixing Processes for Single-Screw Extruders
8.1 Common Mixing Operations for Single-Screw Extruders
8.1.1 Common Mixing Applications
8.2 Dispersive and Distributive Mixing Processes
8.3 Fundamentals of Mixing
8.3.1 Measures of Mixing
8.3.2 Experimental Demonstration of Mixing
8.4 The Melting Process as the Primary Mechanism for Mixing
8.4.1 Experimental Analysis of the Melting and Mixing Capacity of a Screw
8.4.2 Mixing and Barrier-Flighted Melting Sections
8.5 Secondary Mixing Processes and Devices
8.5.1 Maddock-Style Mixers
8.5.2 Blister Ring Mixers
8.5.3 Spiral Dam Mixers
8.5.4 Pin-Type Mixers
8.5.5 Knob Mixers
8.5.6 Gear Mixers
8.5.7 Dynamic Mixers
8.5.8 Static Mixers
8.6 Mixing Using Natural Resins and Masterbatches
8.7 Mixing and Melting Performance as a Function of Flight Clearance
8.8 High Pressures During Melting and Agglomerates
8.9 Effect of Discharge Pressure on Mixing
8.10 Shear Refinement
8.11 Direct Compounding Using Single-Screw Extruders
Nomenclature
References
9 Scaling of Single-Screw Extrusion Processes
9.1 Scaling Rules
9.2 Engineering Design Method for Plasticating Screws
9.2.1 Process Analysis and Simulations
9.3 Scale-Up from a 40 mm Diameter Extruder to an 80 mm Diameter Machine for a PE Resin
9.4 Rate Increase for an 88.9 mm Diameter Extruder Running a HIPS Resin
Nomenclature
References
10 Introduction to Troubleshooting the Extrusion Process
10.1 The Troubleshooting Process
10.2 Hypothesis Setting and Problem Solving
10.2.1 Case Study for the Design of a New Resin
10.2.2 Case Study for a Surface Blemish
10.2.3 Case Study for a Profile Extrusion Process
10.3 Equipment and Tools Needed for Troubleshooting
10.3.1 Maddock Solidification Experiment
10.4 Common Mechanical Problems
10.4.1 Flight Clearance and Hard Facing
10.4.2 Barrel and Screw Alignment
10.4.3 Extruder Barrel Supports
10.4.4 First-Time Installation of a Screw
10.4.5 Screw Breaks
10.4.6 Protection from High-Pressure Events
10.4.7 Gearbox Lubricating Oil
10.4.8 Particle Seals and Viscoseals
10.4.9 Screw Cleaning
10.5 Common Electrical and Sensor Problems
10.5.1 Thermocouples
10.5.2 Pressure Sensors
10.5.3 Electronic Filters and Noise
10.6 Motors and Drive Systems
10.6.1 Motor Efficiencies and Power Factors
10.7 Typical Screw Channel Dimensions
10.8 Common Calculations
10.8.1 Energy Dissipated by the Screw
10.8.2 Screw Geometry Indices
10.9 Barrel Temperature Optimization
10.10 Screw Temperature Profile
10.11 The Screw Manufacturing and Refurbishing Process
10.12 Injection-Molding Plasticators
10.12.1 Calculations for Injection-Molding Plasticators
10.13 New Equipment Installations
10.13.1 Case Study: A Large Diameter Extruder Purchase
10.13.2 Case Study: Extruder and Line Purchase for a New Product
10.13.3 A High-Density Foamed Sheet Product
10.13.4 Summary for New Equipment Installations
Nomenclature
References
11 Contamination in the Finished Product
11.1 Foreign Contaminants in the Extrudate
11.1.1 Melt Filtration
11.1.2 Metal Fragments in the Extrudate
11.1.3 Gas Bubbles in a New Sheet Line
11.2 Gels in Polyolefin Resins
11.2.1 Protocols for Gel Analysis
11.3 Resin Decomposition in Stagnant Regions of a Process
11.3.1 Transfer Lines
11.4 Improper Shutdown of Processing Equipment
11.5 Equipment Purging
11.6 Oxygen Exclusion at the Hopper
11.7 Flight Radii Size
11.8 Drying the Resin
11.9 Color Masterbatches
11.10 Case Studies for Extrusion Processes with Contamination in the Product
11.10.1 Intermittent Crosslinked Gels in a Film Product
11.10.2 Small Gels in an LLDPE Film Product
11.10.3 Degassing Holes in Blow-Molded Bottles
11.11 Contamination in Injection-Molded Parts
11.11.1 Splay Defects for Injection-Molded Parts
11.12 Injection-Molding Case Studies
11.12.1 Injection-Molded Parts with Splay and Poor Resin Color Purge
11.12.2 Black Color Streaks in Molded Parts: Case One
11.12.3 Black Streaks in Molded Parts: Case Two
11.12.4 Silver Streaks in a Clear GPPS Resin Injection-Molded Packaging Part
11.12.5 The Injection-Molding Problem at Saturn
11.13 Gels Caused by a Poorly Designed Transfer Line
11.14 The Incumbent Resin Effect
Nomenclature
References
12 Flow Surging
12.1 An Overview of the Common Causes for Flow Surging
12.1.1 Relationship Between Discharge Pressure and Rate at the Die
12.2 Troubleshooting Flow Surging Processes
12.3 Barrel Zone and Screw Temperature Control
12.3.1 Water- and Air-Cooled Barrel Zones
12.4 Rotation- and Geometry-Induced Pressure Oscillations
12.5 Gear Pump Control
12.6 Solids Blocking the Flow Path
12.7 Case Studies for Extrusion Processes That Flow Surge
12.7.1 Poor Barrel Zone Temperature Control
12.7.2 Optimization of Barrel Temperatures for Improved Solids Conveying
12.7.3 Flow Surging Due to High Temperatures in the Feed Section of the Screw
12.7.4 Flow Surging Due to High Temperatures in the Feed Casing
12.7.5 Flow Surging Due to a Poorly Designed Barrier Entry for GPPS Resin
12.7.6 Solid Blockage at the Entry of a Spiral Mixer
12.7.7 Flow Surging Caused by a Worn Feed Casing and a New Barrel
12.7.8 Flow Surging for a PC Resin Extrusion Process
Nomenclature
References
13 Rate-Limited Extrusion Processes
13.1 Vent Flow for Multiple-Stage Extruders
13.2 Screw Wear
13.3 High-Performance and Barrier Screws for Improved Rates
13.4 Case Studies That Were Rate Limited
13.4.1 Rate Limitation Due to a Worn Screw
13.4.2 Rate Limitation Due to Solid Polymer Fragments in the Extrudate
13.4.3 Rate Limited by the Discharge Temperature for a Pelletizing Extruder
13.4.4 Large Diameter Extruder Running PS Resin
13.4.5 Rate Limited by Discharge Temperature and Torque for Starch Extrusion
13.4.6 Vent Flow for a Two-Stage Screw Running a Low Bulk Density PS Feedstock
13.4.7 Increasing the Rate of a Large Part Blow-Molding Process
Nomenclature
References
14 Barrier and High-Performance Screws
14.1 Barrier Screws
14.2 Wave Dispersion Screws
14.2.1 Double Wave Screw
14.2.2 Energy Transfer Screws
14.2.3 Variable Barrier Energy Transfer Screws
14.2.4 Distributive Melt Mixing Screws
14.2.5 Fusion Screws
14.3 Other High-Performance Screw Designs
14.3.1 Stratablend Screws
14.3.2 Unimix Screws
14.4 Calculation of the Specific Rotation Rate
Nomenclature
References
15 Melt-Fed Extruders
15.1 Simulation Methods
15.2 Compounding Processes
15.2.1 Common Problems for Melt-Fed Extruders on Compounding Lines
15.3 Large-Diameter Pumping Extruders
15.3.1 Loss of Rate Due to Poor Material Conveyance in the Feed Section
15.3.2 Operation of the Slide Valve
15.3.3 Nitrogen Inerting on Vent Domes
15.4 Secondary Extruders for Tandem Foam Sheet Lines
15.4.1 High-Performance Cooling Screws
Nomenclature
References
Appendix A1 Polymer Abbreviation Definitions
Appendix A3 Rheological Calculations for a Capillary Rheometer and for a Cone and Plate Rheometer
A3.1 Capillary Rheometer
A3.2 Cone and Plate Rheometer
References
Appendix A4 Shear Stress at a Sliding Interface and Melting Fluxes for Select Resins
A4.1 Shear Stress at a Sliding Interface for Select Resins
A4.2 Melting Fluxes for Select Resins
References
Appendix A5 Solids Conveying Model Derivations and the Complete LDPE Solids Conveying Data Set
A5.1 Channel Dimensions, Assumptions, and Basic Force Balances
A5.2 Campbell-Dontula Model
A5.2.1 Modified Campbell-Dontula Model
A5.3 Hyun-Spalding Model
A5.4 Yamamuro-Penumadu-Campbell Model
A5.5 Campbell-Spalding Model
A5.6 The Complete Dow Solids Conveying Data Set
References
Appendix A6 Melting Rate Model Development
A6.1 Derivation of the Melting Performance Equations for a Conventional Channel
A6.2 Effect of Static Pressure on Melting
References
Appendix A7 Flow and Energy Equation Development for the Metering Channel
A7.1 Transformed Frame Flow Analysis
A7.1.1 x-Directional Flow
A7.1.2 z-Directional Flow
A7.1.3 z-Directional Flow for Helix Rotation with a Stationary Screw Core and Barrel
A7.1.4 z-Directional Flow Due to a Pressure Gradient
A7.2 Viscous Energy Dissipation for Screw Rotation
A7.2.1 Viscous Energy Dissipation for Screw Rotation: Generalized Solution
A7.2.2 Viscous Energy Dissipation for Screw Rotation for Channels with Small Aspect Ratios (H/W & 0.1)
A7.3 Viscous Energy Dissipation for Barrel Rotation
A7.3.1 Viscous Energy Dissipation for Barrel Rotation: Generalized Solution
A7.3.2 Viscous Energy Dissipation for Barrel Rotation for Channels with Small Aspect Ratios (H/W & 0.1)
References
Author Index
Subject Index

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Analyzing and Troubleshooting Single-Screw Extruders

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