Extruding Plastics

Extruding Plastics A practical processing handbook

D. V. Rosato Plastics Institute of America Rhode Island School of Design Chatham, MA, 02633 USA

| ^ ^ | SPR1NGER-SCIENCE+BUSINESS M E D I A , B .V .

A catalogue record for this book is available from the British Library

ISBN 978-0-412-82810-2 ISBN 978-1-4615-5793-7 (eBook) DOI 10.1007/978-1-4615-5793-7

Copyright <e 1998 by Springer Science+ Business Media Dordrecht Originally published by Chapman & Hall in 1998 Softcover reprint of the hardcover 1st edition 1998 This printing is a digital duplication of the original edition.

All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, mechanical, photo-copying, recording, or otherwise, without the prior written permission of the publisher, Springer-Science+ Business Media, B.V.

Printed on acidjree paper.

Contents

Preface

1 The complete extrusion process Overview Extruder type and construction Extruder operation

Extrusion coating Other lines

Processing plastic Extruder heating and cooling profile Auxiliary equipment Plant operation Plant safety Acceptable risk Energy conservation Processor

Custom Captive Proprietary

Predicting performance Scale-up

Myths and fact People and productivity Processing and patience Troubleshooting History

2 Extrusion machine and line Features of extruder and production line

Overview

xiii

1 1 6

10 13 14 19 22 24 28 32 39 40 42 43 43 43 43 44 44 46 47 47 50

54 54 54

vi

Single-screw extruder Twin-screw extruder

Extruder components Alignment Borescoping Drive system Barrel Barrel and feed unit Auxiliary equipment

Contents

Operating extruder and complete line Planning a line Start-up and shut-down Temperature/pressure and output Maintenance Troubleshooting Training

Coextrusion Melt flow characteristics Types of construction

Selecting equipment Safety

3 Processing plastic material Overview Plastic type Properties Heat profile Melt flow and rheology Melt flow and defect Thermal properties Purging Recycling Drying

4 Plasticizing screw process Overview Screw design

Output Screw torque Screw cooling Performance

Mixing devices Barrier screw Melting action Venting Process performance

56 60 65 67 69 70 75 93 98

116 118 121 125 129 130 142 144 146 150 152 158

160 160 162 168 173 174 178 180 187 188 190

199 199 208 210 212 213 214 216 219 220 221 225

Contents

Wear Screw inspection

5 Die design and performance Overview Melt behavior

Die land Slit Rod Tear drop Temperature Manifold and die Coextrusion dies Special dies

Die design Construction materials Maintenance Troubleshooting

6 Process control and computer Overview Trade-off Sensors Accuracy Integration Intelligent processing

7 Blown film Overview Plastic materials Blown tube characteristics

Start-up Orientation Process optimization

Line control Output rate

Die Multi-layer or coextrusion Film randomization Troubleshooting

8 Flat film Overview

Other type film Flat or blown film

Plastic materials

vii

226 226

228 228 241 242 246 246 246 246 250 256 266 270 273 275 276

283 283 287 290 296 301 304

305 305 312 315 320 323 324 325 326 334 335 338 348

349 349 356 357 358

viii

Flat film characteristics Start-up Shut-down

Orientation Process control

Line control Output rate

Die Troubleshooting

9 Sheet Overview Plastic materials

Processing ABS Processing PET

Orientation Process optimization

Line components Roll stack

Contents

Coextruded or laminated sheets Pull roll Air knife Trim and slitting Antistatic bath Process control Cut-off Winder

Die Applications Troubleshooting

10 Calendering Overview

Calendering or extrusion Calendering operation

Surface finishing Plastic materials,

Fluxing and feeding Heat sensitivity Contamination Recycling

Orientation Processing optimization

Roll

361 362 362 363 367 369 369 370 372

376 376 383 383 386 387 388 388 388 396 400 400 400 401 402 403 406 409 411 412

418 418 420 422 427 430 432 433 434 434 435 435 435

Control Application Safety Costing Troubleshooting

11 Coating and lamination Overview

Substrate Plastic materials Processing characteristics

Shut-down Process optimization

Gauge variation Neck-in Substrate Adhesion Printing

Contents

Block and slip surface quality Control Dimensional stability Heat sealing

Die Applications Safety Troubleshooting

12 Wire and cable Overview Plastic materials Processing characteristics

Other coating lines Start-up

Process optimization Die Troubleshooting

13 Pipe and tube Overview Plastic materials Processing characteristics Process optimization

Orientation Die

ix

437 437 438 438 440

441 441 447 448 449 456 457 457 457 459 460 462 463 463 464 464 464 465 465 466

469 469 471 474 478 483 485 486 493

494 494 501 503 514 518 520

x Contents

Applications 524 Cost 525 Troubleshooting 527

14 Profiles 528 Overview 528 Plastic materials 532 Processing characteristics 533

Coated profile substrate 535 Process optimization 536

Cooling profile 536 Window frame precision fast line 537 Rod 539 Robotic profile 540 Mechanical strength 540

Applications 541 Die 542 Troubleshooting 551

15 Blow molding 552 Overview 552 Plastic materials 554

Coextrusion 556 Processing characteristics 556

Extrusion blow molding 556 Injection blow molding 562 Stretch blow molding 570

Process optimization 574 Die/mold/tool 577 Applications 584 Cost 584 Troubleshooting 592

16 Fiber and filament 593 Overview 593 Plastic materials 595 Processing characteristics 596

Melt spinning 597 Dry spinning 598 Wet spinning 598 Other processes 599 Fiber twist 599 Filtration 600 Nonwoven 601

Contents xi

Spinneret 602 Process optimization 603 Theoretical versus actual value 604 Applications 606 Troubleshooting 606

17 Compounding 608 Overview 608 Plastic materials 609

Blend 615 Processing characteristics 616

Batch compounding 616 Continuous compounding 617 Feeder and blender 618 Reactive compounding 620 Pellet 622 Dicer 627 Type of mixer 628

Process optimization 628 Control 629

Die 629 Troubleshooting 629

18 Other processes 631 Introduction 631 Injection molding 631

Noncontinuous extruder 638 Continuous extruder 640 Mold 641

Injection-compression molding 642 Injection/blow molding with orientation 643 Continuous molding with extruder 645

Velcro strip Ferris wheel molding 645 Carousal molding 650

Thermoforming 650 Scrapless forming 661 Postforming 661 Netting 663 Foam 663

19 Testing and quality control 673 Introduction 673

Quality assurance 674 Testing 675

xii Contents

Type of test Density and specific gravity Melt index Melt rheometer

Quality control Statistical process control

Monitoring process variables Assessing statistical practice

Quality system regulation Extrusion variables

Plastic material Melt flow Process control Product Processing intelligence Judgment and experience Problem and solution

20 Summary Introduction Success by design Cost

Estimating product cost Direct and indirect cost Technology cost modeling

Processing improvement Process types Plant control Energy

Plastic and energy People

Processing and patience Plastics growth with extrusion

Appendices Metric conversion charts Standard metric symbols Mathematical symbols and abbreviations Greek alphabet Properties of water Angle conversions

References

Index

677 677 680 682 686 687 688 689 689 690 691 692 693 695 696 696 697

699 699 700 700 705 706 707 711 712 719 720 721 725 725 725

732 732 735 735 736 736 736

737

755

Preface

Worldwide, extrusion lines successfully process more plastics into prod­ucts than other processes by consuming at least 36 wt% of all plastics. They continue to find practical solutions for new products and/ or prob­lems to meet new product performances.

This book, with its practical industry reviews, is a unique handbook (the first of its kind) that covers over a thousand of the potential combina­tions of basic variables or problems with solutions that can occur from up-stream to down-stream equipment. Guidelines are provided for maxi­mizing processing efficiency and operating at the lowest possible cost. It has been prepared with an awareness that its usefulness will depend greatly upon its simplicity and provision of essential information.

It should be useful to: 0) those already extruding and desiring to obtain additional information for their line and/ or prOVide a means of reviewing other lines that can provide their line with operating improvements; (2) those processing or extruding plastics for the first time; (3) those consider­ing going into another extrusion process; (4) those desiring additional information about employing the design of various products more effi­ciently, with respect to both performance and cost; (5) those contemplat­ing entering the business of extrusion; (6) those in new venture groups, materials development, and/ or market development; (7) those in disci­plines such as nonplastics manufacturers, engineers, designers, quality control, financial, and management; and (8) those requiring a textbook on extrusion in trade schools and high schools or colleges.

Only a few theoretical concepts are included. Persons dealing with practicalities will find the theoretical explanations enlightening and understandable. Theorists will gain insight into the practical limitations of equipment, plastics, and people. There are various excellent books that provide detailed theoretical analysis; they are listed in the Reference sec­tion. However, this review of the industry's operating experiences pre­sented with 387 figures and 128 tables will help make extrusion lines operate more efficiently and expand their capabilities. These experiences establish empirical analyses that, in turn, develop theoretical concepts.

The book's practical approach provides for the novice and experienced

xiv Preface

personnel a description of extrusion advances and trends. This leads to 'streamlining' processing lines by anticipating and understanding prob­lems that could occur, what causes them, how to eliminate them, and/ or how to take corrective action. The content is arranged to provide a natural progression from simple to complex situations. It correlates materials, equipment, process controls, product requirements, and people. Thus, one learns how to avoid 'preventable' down-time and/or unacceptable products. A step-by-step approach is used to simplify and understand practical fundamentals that interrelate processes with plastics-to­products.

This comprehensive book explains in a clear, concise, simple format the different extrusion processes that produce many different commodity and engineered plastic products. Included are: (1) flexible-to-rigid-to-foam-to­decorative constructions; (2) both simple and complex shapes; (3) process­ing virgin and/or recycled plastics; (4) procedures for start-ups and shut-downs; (5) postforming in-line, troubleshooting, and so on. A target has been to open up new possibilities in the art of extruding, with the goal of approaching zero defect processing.

It is essential to re-emphasize what is reviewed in the text, namely that all data and information presented on equipment and plasticS are to be used as guides. Obtain the latest, most complete, information from suppliers.

Information is derived from the author's experience as well as personal contacts with industry worldwide, induding many industry people, and industry sources, as is evident by the references listed at the end of this book. Every possible care has been taken to ensure that the content of this book is correct. While the information contained is believed to be true and accurate, no one, including the editor, contributors, sources, and pub­lisher, can accept any legal responsibility for any errors, omissions, oper­ating risks/ damages, or other factors. All information is provided in good faith but without legal responsibility. This book will serve to help people understand the process of extrusion and that includes maintaining the highest degree of safety and avoiding injury to personnel and damage to equipment.

Information contained in this book may be covered by US and world­wide patents. No authorization to utilize these patents is given or implied; they are discussed for information only. Disclosures are neither a license to operate nor a recommendation to infringe any patent. No attempt has been made to refer to patents by number, title, or ownership.

D. V. Rosato Chatham, MA., USA December, 1997

I