Understanding Plastics Engineering Calculations

Table of Contents

Preface

1 Rheological Properties of Molten Polymers

1.1 Polymer Melt Flow

1.1.1 Apparent Shear Rate

1.1.2 Apparent Viscosity

1.1.3 Power Law of Ostwald and De Waele

1.1.4 Viscosity Formula of Klein

1.1.5 Resin Characterization by Power Law Exponent

1.2 Melt Flow Index

1.3 Relationship between Flow Rate and Pressure Drop

1.4 Shear Rates for Extrusion Dies

References.

2 Thermal Properties of Solid and Molten Polymers

2.1 Specific Volume

2.2 Specific Heat

2.3 Thermal Expansion Coefficient

2.4 Enthalpy

2.5 Thermal Conductivity

2.6 Thermal Diffusivity

2.7 Coefficient of Heat Penetration

2.8 Heat Deflection Temperature

2.9 Vicat Softening Point

References.

3 Heat Transfer in Plastics Processing

3.1 Steady State Conduction

3.1.1 Plane Wall

3.1.2 Cylinder

3.1.3 Hollow Sphere

3.1.4 Sphere

3.1.5 Heat Conduction in Composite Walls

3.1.6 Overall Heat Transfer through Composite Walls

3.2 Unsteady State Conduction

3.2.1 Temperature Distribution in One-Dimensional Solids

3.2.2 Thermal Contact Temperature

3.3 Heat Conduction with Dissipation

3.4 Dimensionless Groups

3.5 Heat Transfer by Convection

3.6 Heat Transfer by Radiation

3.7 Dielectric Heating

3.8 Fick’s Law of Diffusion

3.8.1 Permeability

3.8.2 Absorption and Desorption

3.9 Case Study: Analyzing Air Gap Dynamics in Extrusion Coating by Means of Dimensional Analysis

3.9.1 Heat Transfer Between the Film and the Surrounding Air

3.9.2 Chemical Kinetics

3.9.3 Evaluation of the Experiments

References.

4 Analytical Procedures for Troubleshooting Extrusion Screws

4.1 Three-Zone Screw

4.1.1 Extruder Output

4.1.2 Feed Zone

4.1.3 Metering Zone (Melt Zone)

4.1.4 Practical Design of 3-Zone Screws

4.2 Melting of Solids

4.2.1 Thickness of Melt Film

4.2.2 Melting Profile

4.2.3 Melt Temperature

4.2.4 Melt Pressure

4.2.5 Heat Transfer between the Melt and the Barrel

4.2.6 Screw Power

4.2.7 Temperature Fluctuation of the Melt

4.2.8 Pressure Fluctuation

4.2.9 Extrusion Screw Simulations

4.2.10 Mechanical Design of Extrusion Screws

References.

5 Analytical Procedures for Troubleshooting Extrusion Dies

5.1 Calculation of Pressure Drop

5.1.1 Effect of Die Geometry on Pressure Drop

5.1.2 Shear Rate in Die Channels

5.1.3 General Relationship for Pressure Drop in Any Given Channel Geometry

5.1.4 Examples for Calculating Pressure Drop in the Die Channels of Different Shapes

5.1.5 Temperature Rise and Residence Time

5.2 Spider Dies

5.3 Spiral Dies

5.4 Adapting Die Design to Avoid Melt Fracture

5.4.1 Pelletizer Dies

5.4.2 Blow Molding Dies

5.4.3 Summary of the Die Design Procedures

5.5 Flat Dies

5.6 An Easily Applicable Method of Designing Screen Packs for Extruders

5.7 Parametrical Studies

5.7.1 Pipe Extrusion

5.7.2 Blown Film

5.7.3 Thermoforming

References.

6 Analytical Procedures for Troubleshooting Injection Molding

6.1 Effect of Resin and Machine Parameters

6.1.1 Resin-Dependent Parameters

6.1.2 Mold Shrinkage and Processing Temperature

6.1.3 Drying Temperatures and Times

6.2 Melting in Injection Molding Screws

6.2.1 Model

6.2.2 Results of Simulation

6.2.3 Screw Dimensions

6.3 Injection Mold

6.3.1 Runner Systems

6.3.2 Mold Filling

6.4 Flow Characteristics of Injection Molding Resins

6.4.1 Model

6.4.2 Melt Viscosity and Power Law Exponent

6.4.3 Experimental Results and Discussion

6.5 Cooling of Melt in the Mold

6.5.1 Thermal Design of the Mold

6.6 Mechanical Design of the Mold

6.7 Rheological Design of the Mold

References.

Summary

Appendix: List of Programs with Brief Descriptions

Index

Biography