Practical Guide to Rotational Moulding

Practical Guide to Rotational Moulding
Roy J. Crawford and Mark P. Kearns
Queen’s University, Belfast
Contents
Preface . v
Chapter 1 – Introduction to the Rotational Moulding Process . 1
1.1 Introduction 1
1.2 The Rotational Moulding Process 8
1.3 Overview of Rotational Moulding . 16
1.4 Special Nature of Rotational Moulding . 18
1.5 Advantages of Rotational Moulding . 20
1.6 Disadvantages of Rotational Moulding . 21
1.7 Common Applications for Rotomoulded Products 22
1.7.1 Material Handling Products . 22
1.7.2 Industrial Products 23
1.7.3 Environmental Products 23
1.7.4 Leisure Products . 24
1.7.5 Marine Products 24
1.7.6 Road Signage . 25
Bibliography 26
Chapter 2 – Moulds 29
2.1 Introduction 29
2.2 Mould Materials . 30
2.3 Sheet Steel 30
2.4 Aluminium 31
2.5 Electroformed Nickel . 31
2.6 Comparison Between Mould Materials 32
2.7 Mould Design 33
2.7.1 Mould Frame 34
2.7.2 Moulded-in Inserts 35
2.7.3 Moulded-in Handles 36
2.7.4 Temporary Inserts . 36
2.7.5 Movable Cores . 37
2.7.6 Threads 38
2.7.7 Mould Venting . 39
2.7.8 Mould Surface Finish 40
2.8 Mould Release 41
2.8.1 Mould Preparation for Release Agent . 41
2.8.2 Reactive Systems . 42
2.8.2.1 Spray-on Zinc Stearates 42
2.8.2.2 Silicones 42
2.8.2.3 Disiloxanes 42
2.8.3 Conventional Systems 43
2.8.4 Permanent Systems . 43
2.8.5 Hybrid Systems 44
2.9 Mould Cooling . 44
2.10 Mould Ancillaries . 47
2.11 Moulding Aids 49
2.12 Kiss-Offs 51
2.13 Calculation of Charge Weight 52
Chapter 3 – Rotational Moulding Machinery . 55
3.1 Introduction 55
3.2 Types of Rotational Moulding Machines 55
3.2.1 Carousel Machines . 55
3.2.2 Shuttle Machines 57ii
3.2.3 Clamshell Machines 58
3.2.4 Rock and Roll Machines 61
3.2.5 Other Types of Machines 63
3.3 Mould Swing 66
3.4 Mould Speed 68
3.5 Speed Ratio .68
3.6 Oven Air Flow Amplification .69
3.7 Cooling .71
3.8 Developments in Machine Control 71
3.9 Internal Air Temperature Measurement in Rotational Moulding 72
3.10 Preparation of Rotolog for Moulding Trials .76
3.11 Monitoring Pressure Inside a Mould .80
Bibliography .87
Chapter 4 – Materials for Rotational Moulding 89
4.1 Introduction 89
4.2 Typical Characteristics of Rotationally Moulded Plastics 90
4.3 Materials Used in Rotational Moulding .90
4.4 Polyethylene 92
4.4.1 Low Density Polyethylene (LDPE) .94
4.4.2 High Density Polyethylene (HDPE) .94
4.4.3 Medium Density Polyethylene (MDPE) 94
4.4.4 Linear Low Density Polyethylene (LLDPE) 94
4.4.5 Metallocene Polyethylene 95
4.4.6 Ethylene-Vinyl Acetate (EVA) 95
4.4.7 Ethylene-Butyl Acrylate (EBA) .96
4.5 Polypropylene (PP) 96
4.6 Polyamides (Nylons) 96
4.6.1 Nylon 6 96
4.6.2 Nylon 11 and Nylon 12 97
4.6.3 Reaction Injection Moulding (RIM) Nylon .97
4.7 Amorphous Materials .97
4.7.1 Polyvinyl Chloride (PVC) .97
4.7.2 Fluoropolymers .97
4.8 Other Plastics .98
4.9 Additives Used in Rotational Moulding Materials 99
4.9.1 Fillers 99
4.9.2 Plasticisers 100
4.9.3 Lubricants .100
4.9.4 Stabilisers .100
4.9.5 Anti-Oxidants .100
4.9.6 Ultraviolet Stabilisers .100
4.9.7 Flame Retardants 101
4.9.8 Crosslinking Agents .101
4.9.9 Foaming Agents 101
4.9.10 Pigments .104
4.10 Powders for Rotational Moulding – Grinding or Pulverising 105
4.10.1 Introduction .105
4.11 Particle Size Distribution 111
4.12 Dry Flow .112
4.13 Bulk Density .114
4.14 Factors Affecting Powder Quality .115
4.14.1 Gap Size .115
4.14.2 Number of Mill Teeth .116
4.14.3 Grinding Temperature .116iii
4.15 Micropelletising 117
4.16 Colouring of Plastics for Rotational Moulding . 118
4.17 Types of Pigments . 121
Bibliography 123
Chapter 5 – Quality Control in Rotational Moulding . 129
5.1 Introduction 129
5.2 Wall Thickness Distribution 129
5.3 Shrinkage 133
5.3.1 Shrinkage Guidelines 133
5.3.2 Control of Shrinkage . 134
5.3.2.1 Effect of Release Point on Shrinkage . 134
5.3.2.2 Other Factors Affecting Shrinkage . 135
5.4 Warpage 136
5.4.1 Control of Warpage . 137
5.5 Residual Stress . 140
5.5.1 Short-Term Effects of Residual Stresses 142
5.5.2 Long-Term Effects of Residual Stresses . 143
5.5.3 Cures for Residual Stress Problems . 144
5.6 Surface Decoration 144
5.6.1 Painting 144
5.6.2 Hot Stamping 145
5.6.3 Adhesives . 146
5.6.4 In-Mould Decoration . 146
5.6.5 Post Moulding Decoration . 150
5.7 Foaming in Rotational Moulding 151
5.7.1 Chemical Blowing Agent Technology 153
5.7.2 Design of Foamed Sections 154
5.7.3 Solid/Foam Cross-Sections 156
5.7.4 Solid/Foam/Solid Cross-Sections 156
Bibliography 158
Chapter 6 – The Future for Rotational Moulding . 163
6.1 Materials 163
6.2 Moulds . 164
6.3 Moulding Equipment 166
6.4 The Challenges . 168
6.5 The Role that the Moulder Must Play . 168
6.6 The Role that the Suppliers Must Play . 169
Abbreviations and Acronyms . 171
Index
لمة سر فك الضغط : books-world.net
The Unzip Password : books-world.net