James L. White /David D. ChoiPolyolefi ns

Polyolefi ns

James L. WhiteDavid D. Choi

Hanser Publishers, Munich • Hanser Gardner Publications, Cincinnati

Processing, Structure Development,and Properties

The Authors:Professor Dr. James L. White and Dr. David D. Choi, Department of Polymer Engineering,The University of Akron, 250 South Forge Street, Akron, OH, 44325-0301, USA(Dr. David D. Choi is currently with Asahi Thermofil, inc.; One Thermofil Way, Fowlerville, MI 48836, USA)

Distributed in the USA and in Canada byHanser Gardner Publications, Inc.6915 Valley Avenue, Cincinnati, Ohio 45244-3029, USAFax: (513) 527-8801Phone: (513) 527-8977 or 1-800-950-8977Internet: http://www.hansergardner.com

Distributed in all other countries byCarl Hanser VerlagPostfach 86 04 20, 81631 München, GermanyFax: +49 (89) 98 48 09Internet: http://www.hanser.de

The use of general descriptive names, trademarks, etc., in this publication, even if the former are not especiallyidentified, is not to be taken as a sign that such names, as understood by the Trade Marks and MerchandiseMarks Act, may accordingly be used freely by anyone.

While the advice and information in this book are believed to be true and accurate at the date of going to press,neither the authors nor the editors nor the publisher can accept any legal responsibility for any errors oromissions that may be made. The publisher makes no warranty, express or implied, with respect to the materialcontained herein.

Library of Congress Cataloging-in-Publication DataWhite, James L.

Polyolefins : processing, structure development & properties / James L.White, David Choi.-- 1st ed.

p. cm.ISBN 1-56990-369-7 (hardcover)1. Polyolefins. I. Choi, David. II. Title.TP1180.P67W48 2004668.4'234--dc22

2004014996

Bibliografische Information Der Deutschen BibliothekDie Deutsche Bibliothek verzeichnet diese Publikation in der Deutschen Nationalbibliografie;detaillierte bibliografische Daten sind im Internet über <http://dnb.ddb.de> abrufbar.ISBN 3-446-22962-0

All rights reserved. No part of this book may be reproduced or transmitted in any form or by any means,electronic or mechanical, including photocopying or by any information storage and retrieval system, withoutpermission in wirting from the publisher.

© Carl Hanser Verlag, Munich 2005Production Management: Oswald ImmelTypeset by Manuela Treindl, Laaber, GermanyCoverconcept: Marc Müller-Bremer, Rebranding, München, GermanyCoverdesign: MCP • Susanne Kraus GbR, Holzkirchen, GermanyPrinted and bound by Druckhaus “Thomas Müntzer”, Bad Langensalza, Germany

Preface

Polyolefins, i.e., the polymers synthesized from olefinic monomers, are the majorcommercial thermoplastics. They are also important components of major thermoplasticelastomers. Polyethylene and polypropylene are the two largest thermoplastics in volumeand are fabricated into filaments, films, and molded parts.

The book treats the history, commercialization, characterization, and crystallographyof various commercial polyolefins and polystyrenes and describes development ofstructure during fabrication of these polymers into various shapes. It is in this latterarea that this book is unique. No other volume describes the structuring of moltenpolyolefins in fiber, film, and molding processes with correlations between structuralorder such as crystalline unit cell, polymorphic effects and orientation with processingparameters.

We have incorporated polystyrene into this book although it is not classified as apolyolefin, but rather as an aromatic vinyl polymer. The structure and behavior of itsisotactic and syndiotactic forms are similar to those of the corresponding polyolefinsand help the drawing of conclusions. Atactic polystyrene vitrifies into a glass (solidifiedmelt) and lets us know the fundamentals of structuring in polymers prior to crystalli-zation in polymer processing operations.

Throughout the book we made direct comparisons of the structure and behavior ofpolyethylene, isotactic and syndiotactic polypropylenes, isotactic polybutene-1, isotacticpoly(4-methyl pentene-1), and the different polystyrenes. This book should be of interestto engineers, chemists, and technologists working with polyolefins.

The book was written while both authors were affiliated with the Department andInstitute of Polymer Engineering at the University of Akron.

James L. WhiteDavid Dongman Choi

We dedicate this bookto our wives

Alganesh Tereste Whiteand

Hyeon Park Choi

Contents

Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . V

1 Origins of Polyolefins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.1 Introduction and Prehistory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2 Polyethylene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

1.2.1 Low Density Polyethylene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.2.2 Karl Ziegler and High Density Polyethylene . . . . . . . . . . . . . . . . . 31.2.3 Standard Oil of Indiana . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51.2.4 Phillips Petroleum and High Density Polyethylene . . . . . . . . . . . 51.2.5 Linear Low Density Polyethylene . . . . . . . . . . . . . . . . . . . . . . . . . . 6

1.3 Isotactic Polypropylene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71.3.1 Giulio Natta, Milan Politechnico and Montecatini . . . . . . . . . . . 71.3.2 Standard Oil of Indiana and Phillips Petroleum . . . . . . . . . . . . . 8

1.4 Isotactic Polybutene-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91.5 Isotactic Polymers of Higher Olefins and Poly(4-Methyl Pentene-1) . . 101.6 Ethylene-Propylene Rubber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111.7 Metallocene Polymerization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121.8 Stereoregular Polystyrenes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

1.8.1 Isotactic Polystyrene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131.8.2 Syndiotactic Polystyrene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

1.9 Syndiotactic Polypropylene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141.10 Cyclopolyolefins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141.11 New Metallocene Polyolefin Copolymers . . . . . . . . . . . . . . . . . . . . . . . . 161.12 Current Production Levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161.13 Bulk Polymer Properties and Chemical Stability . . . . . . . . . . . . . . . . . . 17References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

2 Characterization Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232.2 Asymmetric Carbon Atoms and Tacticity . . . . . . . . . . . . . . . . . . . . . . . . 23

2.2.1 Low Molecular Weight Compounds . . . . . . . . . . . . . . . . . . . . . . 232.2.2 Polyolefins [5] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242.2.3 Tacticity Levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

VIII Contents

2.3 Crystallinity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272.4 Crystal Structure [16, 17] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 282.5 Chain Conformations in Crystals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 322.6 Molecular Weight Distribution [7, 34, 35] . . . . . . . . . . . . . . . . . . . . . . . . 332.7 Orientation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

2.7.1 Uniaxial Orientation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 372.7.2 Biaxial Orientation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

2.8 Superstructure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

3 Crystallography of Polyolefins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 493.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 493.2 Early Investigations of Low Molecular Weight Paraffinic Compounds 493.3 Polyethylene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 553.4 Isotactic Polypropylene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 583.5 Syndiotactic Polypropylene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 603.6 Isotactic Polybutene-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 623.7 Syndiotactic Polybutene-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 633.8 Isotactic Poly(4-Methyl Pentene-1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 633.9 Isotactic Polymers of Other α-Olefins . . . . . . . . . . . . . . . . . . . . . . . . . . . 653.10 Isotactic Polystyrene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 663.11 Syndiotactic Polystyrene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 673.12 Summary and Trends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

4 Single Crystals: Structural Hierarchy and Morphology . . . . . . . . . . . . . . . . . 754.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 754.2 Polyethylene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

4.2.1 Single Crystals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 754.2.2 Flow-Induced Structures from Solution . . . . . . . . . . . . . . . . . . . 774.2.3 Bulk Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78

4.3 Isotactic Polypropylene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 804.3.1 Single Crystals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 804.3.2 Flow-Induced Structures from Solution . . . . . . . . . . . . . . . . . . . 804.3.3 Bulk Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

4.4 Syndiotactic Polypropylene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 824.5 Isotactic Polybutene-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

4.5.1 Single Crystals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 834.5.2 Bulk Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

IXContents

4.6 Isotactic Poly(4-Methyl Pentene-1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 844.6.1 Single Crystals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 844.6.2 Flow-Induced Structures from Solution . . . . . . . . . . . . . . . . . . . 844.6.3 Bulk Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85

4.7 Isotactic Polystyrene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 854.7.1 Single Crystals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 854.7.2 Flow-Induced Structures from Solution . . . . . . . . . . . . . . . . . . . 864.7.3 Bulk Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

4.8 Syndiotactic Polystyrene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 874.8.1 Single Crystals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 874.8.2 Bulk Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87

4.9 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

5 Spherulites and Quiescent Crystallization . . . . . . . . . . . . . . . . . . . . . . . . . . . . 915.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 915.2 Spherulites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91

5.2.1 Quiescently Crystallized Polymers . . . . . . . . . . . . . . . . . . . . . . . . 915.2.2 Polyethylene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 915.2.3 Isotactic Polypropylene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 935.2.4 Syndiotactic Polypropylene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 945.2.5 Isotactic Polybutene-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 945.2.6 Isotactic Poly(4-methyl pentene-1) . . . . . . . . . . . . . . . . . . . . . . . 955.2.7 Isotactic Polystyrene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 955.2.8 Syndiotactic Polystyrene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95

5.3 Quiescent Crystallization Kinetics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 965.3.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 965.3.2 Polyethylene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 985.3.3 Isotactic Polypropylene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 995.3.4 Syndiotactic Polypropylene . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1005.3.5 Isotactic Polybutene-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1005.3.6 Isotactic Polystyrene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1005.3.7 Syndiotactic Polystyrene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

5.4 Time-Temperature Transformation and Continuous CoolingTransformation Plots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

5.5 Summary and Perspectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103

X Contents

6 Polyolefin Copolymers and Blends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1076.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1076.2 Stereoblock Copolymers [1, 2] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1086.3 Copolymers of Polyethylene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109

6.3.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1096.3.2 Ethylene-Propylene Copolymers (EPM) . . . . . . . . . . . . . . . . . . 1106.3.3 Ethylene-Butene-1/Hexene-1 Copolymers . . . . . . . . . . . . . . . . 1116.3.4 Ethylene-Octene Copolymers . . . . . . . . . . . . . . . . . . . . . . . . . . . 1116.3.5 Ethylene-Styrene Copolymers . . . . . . . . . . . . . . . . . . . . . . . . . . 1136.3.6 Ethylene-Cyclopentene/Norbornene Copolymers . . . . . . . . . . 113

6.4 Copolymers of Polypropylene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1146.4.1 Isotactic Polypropylene with Ethylene [53] . . . . . . . . . . . . . . . 1146.4.2 Isotactic Polypropylene with Other Monomers . . . . . . . . . . . . 1156.4.3 Syndiotactic Polypropylene with Butene-1 . . . . . . . . . . . . . . . . 115

6.5 Blends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1156.5.1 Inter-Polyolefin Homopolymer Miscibility . . . . . . . . . . . . . . . 1156.5.2 Polypropylene-Ethylene Copolymer Blends . . . . . . . . . . . . . . . 1166.5.3 Polypropylene Dynamic Vulcanizates [68] . . . . . . . . . . . . . . . . 116

6.6 Perspective . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

7 Polymer Melt Processing, Rheological Properties, and Orientation inFlowing Polymer Melts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1217.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1217.2 Polymer Melt Processing Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . 121

7.2.1 Single Screw Extrusion [1, 2] . . . . . . . . . . . . . . . . . . . . . . . . . . . 1217.2.2 Twin Screw Extrusion and Polyolefin

Modification/Grafting [2–4] . . . . . . . . . . . . . . . . . . . . . . . . . . . 1227.2.3 Die Extrusion [11] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124

7.3 Rheological Properties of Polymer Melts . . . . . . . . . . . . . . . . . . . . . . . . 1267.4 Effects of Additives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1317.5 Early Observations of Flow Birefringence . . . . . . . . . . . . . . . . . . . . . . . 1317.6 Flow Birefringence and Stress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1327.7 Stress Optical Coefficients and Molecular Structure . . . . . . . . . . . . . . 1347.8 Orientation Factors and Stress in Melts . . . . . . . . . . . . . . . . . . . . . . . . . 1357.9 Flow in Dies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136

7.9.1 Flow Patterns and Flow Birefringence . . . . . . . . . . . . . . . . . . . . 1367.9.2 Unstable Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1387.9.3 Flow Structuring of Polyolefins . . . . . . . . . . . . . . . . . . . . . . . . . 138

XI

7.10 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140

8 Melt Spinning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1458.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1458.2 Melt Spinning Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145

8.2.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1458.2.2 Continuous Filaments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1478.2.3 Bulked Continuous Filament Yarns . . . . . . . . . . . . . . . . . . . . . . 1478.2.4 Staple Fibers [15] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1478.2.5 Spunbonded Fabrics [14, 18–21] . . . . . . . . . . . . . . . . . . . . . . . . 1488.2.6 Melt-Blown Fabrics [14] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149

8.3 Dynamics, Heat Transfer, and Modeling in Melt Spinning . . . . . . . . . 1498.3.1 Dynamics and Heat Balance . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1498.3.2 Modeling of Melt Spinning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151

8.4 Melt Flow Instabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1528.4.1 Die Flow (see also Section 7.9.2) . . . . . . . . . . . . . . . . . . . . . . . . 1528.4.2 Spinline Disturbances/Instabilities . . . . . . . . . . . . . . . . . . . . . . 153

8.5 Melt Spinning of Vitrifying Polyhydrocarbons . . . . . . . . . . . . . . . . . . . 1548.5.1 Atactic Polystyrene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1548.5.2 Cyclopolyolefins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1558.5.3 Other Vitrifying Thermoplastics . . . . . . . . . . . . . . . . . . . . . . . . 1568.5.4 Modeling of Orientation-Birefringence Development . . . . . . 156

8.6 Polyethylene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1578.6.1 High-Density Polyethylene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1578.6.2 Ultrahigh Modulus Polyethylene Fibers . . . . . . . . . . . . . . . . . . 1618.6.3 Polyethylene Copolymers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1618.6.4 Polyethylene-Polystyrene Blends . . . . . . . . . . . . . . . . . . . . . . . . 162

8.7 Isotactic Polypropylene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1638.7.1 High Tacticity Polymers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1638.7.2 Lower Tacticity Polymers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1688.7.3 Isotactic Polypropylene-Particulate Compounds . . . . . . . . . . . 1718.7.4 Isotactic Polypropylene Blends . . . . . . . . . . . . . . . . . . . . . . . . . . 1718.7.5 Isotactic Polypropylene Thermoplastic Dynamic

Vulcanizates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1728.8 Syndiotactic Polypropylene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1738.9 Isotactic Polybutene-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1758.10 Isotactic Poly(4-Methyl Pentene-1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1768.11 Syndiotactic Polystyrene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177

Contents

XII

8.12 Trends and Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179

9 Film Processing and Profile Extrusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1859.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1859.2 Film Extrusion Processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185

9.2.1 Cast Film Extrusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1859.2.2 Tubular Blown Film Extrusion . . . . . . . . . . . . . . . . . . . . . . . . . . 1869.2.3 Tentering Frame for Biaxially Oriented Film [12] . . . . . . . . . . 1879.2.4 Double Bubble Process for Biaxially Oriented Film [13] . . . . . 188

9.3 Dynamics, Heat Transfer, and Modeling . . . . . . . . . . . . . . . . . . . . . . . . 1899.3.1 Cast Film Extrusion [16–18] . . . . . . . . . . . . . . . . . . . . . . . . . . . 1899.3.2 Tubular Blown Film Extrusion . . . . . . . . . . . . . . . . . . . . . . . . . . 190

9.4 Melt Flow and Solidification Instabilities . . . . . . . . . . . . . . . . . . . . . . . . 1929.4.1 Haze and Surface Roughness . . . . . . . . . . . . . . . . . . . . . . . . . . . 1929.4.2 Die Flow Produced Extrudate Distortion . . . . . . . . . . . . . . . . . 1949.4.3 Cast Film Instabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1949.4.4 Bubble Instabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195

9.5 Profile Extrusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1969.6 Atactic Polystyrene Film . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197

9.6.1 Tubular Blown Film . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1979.6.2 Biaxially Stretched Film . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198

9.7 Polyethylene Film . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1999.8 Isotactic Polypropylene Film . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202

9.8.1 Cast Film . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2029.8.2 Tubular Blown Film . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2039.8.3 Biaxially Oriented Film . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204

9.9 Syndiotactic Polypropylene Film . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2049.10 Isotactic Polybutene-1 Film . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2069.11 Isotactic Poly(4-Methyl Pentene-1) Film . . . . . . . . . . . . . . . . . . . . . . . . 2069.12 Syndiotactic Polystyrene Film . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2069.13 Summary and Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208

10 Molding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21310.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21310.2 Molding Processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213

10.2.1 Compression Molding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21310.2.2 Injection Molding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214

Contents

XIII

10.2.3 Blow Molding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21910.2.4 Thermoforming [31] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22010.2.5 Scrapless Forming [32] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22110.2.6 Rotational Molding [33] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221

10.3 Dynamics, Heat Transfer, and Modeling . . . . . . . . . . . . . . . . . . . . . . . . 22210.3.1 Injection Molding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22210.3.2 Blow Molding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225

10.4 Atactic Polystyrene and Vitrifying Polyolefins . . . . . . . . . . . . . . . . . . . . 22610.4.1 Injection Molding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22610.4.2 Blow Molding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22710.4.3 Modeling of Orientation-Birefringence Development . . . . . . 227

10.5 Polyethylene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22910.5.1 Injection Molding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22910.5.2 Blow Molding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23110.5.3 Rotational Molding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232

10.6 Isotactic Polypropylene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23210.7 Syndiotactic Polypropylene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23310.8 Isotactic Poly(4-Methyl Pentene-1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23410.9 Isotactic Polystyrene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23510.10 Syndiotactic Polystyrene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23510.11 Trends and Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236

11 Mechanical Properties of Polyolefins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24111.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24111.2 Stress and Small Strain Elasticity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24111.3 Influence of Molecular Weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24311.4 Influence of Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24311.5 Influence of Crystallinity and Comparisons to Other Materials . . . . . 24411.6 Uniaxial Large Strain Behavior [3, 4] . . . . . . . . . . . . . . . . . . . . . . . . . . . 24511.7 Mechanical Properties of Melt-Spun/Drawn Fibers . . . . . . . . . . . . . . . 24511.8 High Modulus Polyolefin Fibers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24811.9 Mechanical Properties of Films . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24811.10 Mechanical Property Modification by Copolymerization and

Blending . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250

Subject Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251

Author Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255

Contents

1 Origins of Polyolefins

1.1 Introduction and Prehistory

In this chapter, the invention and commercial development of several importantpolyolefins, especially crystalline polyolefin thermoplastics will be described. We willconsider the development of low density polyethylene (LDPE) in the 1930s and continuewith high density polyethylene (HDPE) and the isotactic polyolefins of the 1950s andlater, and will also briefly discuss ethylene-propylene rubber. We will also describe thenewer metallocene syndiotactic polyolefins and cyclopolyolefins of the 1980s and 1990s.It is presumed that the reader is aware of various features of polyolefin structure includingtacticity and branching. Details on these structural features are given in Chapter 2.

It is useful to begin with some perspective. It was only in the 1920s with the efforts ofH. Staudinger [1, 2] that the structure of polymers as long chain molecules waselucidated. The importance of the ability to synthesize these materials and theircommercial possibilities were realized by industrial firms around the world. The leadingcompany in this regard, which was cited by Staudinger in his book [2], was the GermanI. G. Farbenindustrie (a combine of Farbenfabriken Bayer, BASF and Farbwerke Hoechstcreated in 1925). It developed atactic polystyrene, polyvinyl chloride, butadiene-acrylo-nitrile rubber, and butadiene-styrene rubber in subsequent years. Also commercializedwas the relatively small volume polyolefin elastomer, polyisobutylene. The two earlyI. G. Farbenindustrie hydrocarbon polymers were:

CH2-CHCH2-CH CH2-C

CH3

CH3

CH2-C

CH3

CH3

(1-I)

Both of these were primarily manufactured in the old BASF facility in Ludwigshafen.The I. G. Farbenindustrie activities and those of the American E. I. du Pont de Nemourswere also much more aggressive than initially those for polyethylene, which we willpresently discuss. The 1950s were to be the major period of polyolefin development.

2 1 Origins of Polyolefins [Refs. on p. 19]

1.2 Polyethylene

1.2.1 Low Density Polyethylene

The development of a commercial polyethylene was due to the efforts of the large Englishchemical company, Imperial Chemical Industries [3, 4], in the 1920s and 30s to makeuse of the high pressure chemistry based on the activities of Prof. A. Michels inAmsterdam. Based on his activities, research was established at the ICI Dyestuff Divisionin the early 1930s in Winnington, England. The high pressure apparatus was delivered,and work began in 1931. The principal researchers were E. W. Fawcett and R. O. Gibson.A 1934 paper by Fawcett and Gibson [5] describes their research perspectives.

In some of their experiments, ethylene was heated under pressure in the range of 1000to 2000 atmospheres. Although traces of white powder were found, they were notrecognized as polyethylene. Subsequently, Fawcett and Gibson sought to react ethyleneand benzaldehyde at 1960 atmospheres and 170 °C. A waxy solid substance was producedand its analysis was found to have the empirical formula CH2, that is

CH2 nCH2 n or CH2-CH2 nCH2-CH2 n (1-II)

The experiment was difficult to reproduce, and their efforts were discontinued in March1933.

Later, work began using a new apparatus, which possessed greater safety characteristics.The new generation of experiments involved M. W. Perrin and J. G. Paton. Perrin, likeGibson, had worked with Michels in Amsterdam. Perrin and Paton began theirexperiments in December 1935 and soon, by using conditions similar to Fawcett andGibson, produced high-molecular weight polyethylene. At higher pressures (3000atmospheres), they obtained higher conversions. It came to be realized that some oxygenwas needed as a polymerization initiator. ICI filed a provisional patent specification inFebruary 1936 in the names of Fawcett, Gibson, Perrin, Paton and Williams [6]. Thedensity of this polyethylene was 0.91 g/cm3.

ICI soon decided to scale up and commercially produce polyethylene. Compressors tocontinuously deliver ethylene at pressures up to 3000 atmospheres were ordered. Thesewere to be designed by Michels, and a pilot plant was built in Winnington. The pilotplant ran intermittently until March 1938. Commercial production began at theWallersford Works in May 1938. One ton of polyethylene was produced in 1938, 10.5 tonsin 1939, 106 tons in 1940 and 576 tons by 1942.

31.2 Polyethylene

In a 1940 paper, Fox and Martin [7] showed by infrared spectroscopy that there weremore methyl groups in the ICI high pressure polyethylenes than could be accountedfor by chain ends. This led to the realization that these polyethylenes had significantamounts of branching.

Dupont obtained a license from ICI to produce polyethylene. During World War IIalternate processes for producing free radical polyethylene were developed by the I. G.Farbenindustrie in Germany (Ludwigshafen) and by Union Carbide in the United States.

At this time, low density polyethylene was primarily used for film packaging.

1.2.2 Karl Ziegler and High Density Polyethylene

Karl Ziegler was a pioneer of organometallic polymerization. He had been a doctoratestudent of Karl von Auwers at the University of Marburg. It was known that metals,such as sodium, could polymerize butadiene and similar monomers. BASF in Ludwigs-hafen had practiced such polymerization during World War I. Ziegler’s efforts tosynthesize organometallic compounds and polymerize new polymers with them dateto the early 1920s. He became interested in the alkyl compounds of potassium andsodium [8]. Ziegler obtained a position at the University of Heidelberg in 1927. Shortlythereafter, Ziegler and Bahr [9] published a study, which showed that oligomers andpolymers of butadiene and styrene can be produced using alkali alkyls.

In 1930, Ziegler and Colonius [10] synthesized alkyl lithium compounds includingbutyl lithium. In subsequent years, Ziegler and his coworkers [11–13] polymerizedvarious hydrocarbons with organo lithium, sodium, and potassium initiators. Specialemphasis was given to polymerization of butadiene. During this period, Ziegler et al.[13] discovered the phenomenon of ‘living polymerization’ with alkyl lithium initiators.It is possible that Ziegler in this period was influenced by synthetic rubber activities atthe I. G. Farbenindustrie (BASF) in nearby Ludwigshafen. In the 1950s, Ziegler’s alkyllithium initiator became widely used in the synthetic rubber industry in the manufactureof polybutadienes, polyisoprenes, and butadiene-styrene copolymers of controlledmicro-structure. The living polymerization technique was subsequently used to makeblock copolymers.

In 1937 Ziegler moved from the University of Heidelberg to the University of Halle/Saal [14]. In 1943, he became the director of the Institut für Kohleforschung in Mülheimnear Essen and Cologne (Köln). Here he was asked to transfer his polymerization effortsfrom butadiene to ethylene. Not surprisingly, he began his research using ethyl lithium.With ethyl lithium, he was able to polymerize higher linear chain alkyls and the

4 1 Origins of Polyolefins [Refs. on p. 19]

corresponding alcohols and acids [8, 15]. There were, however, unlike in the polymeriza-tion of butadiene, limitations to the molecular weight that could be achieved beforedegradation of the active site. Ziegler and Gellert [8, 15] then used the newly introducedLiAlH4 as an initiator and found that they could achieve higher molecular weights.

From the late 1940s, Ziegler and his coworkers turned their attention to synthesizingaluminum alkyls [8, 16] and using them as initiators for polyethylene. Ziegler wasencouraged enough to file patent applications with Gellert [17] as early as 1950 (inGermany) on polymerization of ethylene with aluminum trialkyls as well as alkyls ofberyllium, gallium and indium.

These ‘Aufbau’ reactions of Ziegler attracted the attention of the Italian firm Montecatiniand Giulio Natta of Milan Politechnico. Montecatini took out a license on Ziegler andGellert’s patent as did Farbwerke Hoechst in Frankfurt-am-Main and the AmericanHercules Powder Company [18]. As a part of the Montecatini agreement, Natta wasable to place research assistants in Ziegler’s Mülheim laboratory at this time.

However, inconsistent results were obtained in the Ziegler-Gellert system. The causewas traced to impurities in the reaction system such as nickel. Ziegler and his colleaguesthen looked for co-catalysts to use with the aluminum alkyls. Titanium containing co-catalysts were found to be most effective. Ziegler and his colleagues [19, 20] reportedthe development of the Ziegler-Mülheim process in papers published in 1954 and 1955.

Ziegler’s polyethylene differed from ICI’s material in having a higher density and ahigher crystalline melting temperature. Its tensile modulus and tensile strength werealso much higher. Ziegler and his coworkers concluded that they had made a linearpolyethylene. Ziegler, H. Breil, E. Holzkamp, and H. Martin began filing patents aroundthe world in November 1953. The patents were assigned to Ziegler. The first patent wasfiled in Germany, then elsewhere and about a year later in the USA [21]. Ziegler et al.’spatent claims a catalyst of aluminum trialkyl with salts, oxides, or hydroxides of metalsof the Periodic Table groups IV-B, V-B and III-B. Ziegler et al.’s US patent included theinitiators

• aluminum trialkyl-titanium tetrachloride,

• aluminum trialkyl-zirconium acetylacetonate,

• aluminum trialkyl-thorium acetylacetonate,

• aluminum trialkyl-uranium tetrachloride,

• aluminum trialkyl-vanadium acetylacetonate,

• aluminum trialkyl-chromium acetylacetonate,

5

• aluminum trialkyl-tungsten hexachloride,

• aluminum trialkyl-molybdenum acetylacetonate,

• aluminum trialkyl-zirconium tetrabromide,

• aluminum trialkyl K2TiF6, and

• aluminum trialkyl-zirconium tetrabutylate.

Farbwerke Hoechst (later Hoechst A. G. and more recently Celanese A. G./Ticona), BASFA. G., Farbenfabriken Bayer A. G., and Chemische Werke Hüls were the successors ofthe I. G. Farbenindustrie. Farbwerke Hoechst was already in contact with Karl Ziegleras described earlier. They obtained a license from him in August 1954 and became thefirst manufacturer of the Ziegler high density linear polyethylene. A large manufacturingplant producing 250 tons (500,000 lbs) per month was in operation at the end of 1955[22].

Other licenses went to Chemische Werke Hüls (later part of Degussa) and Ruhrchemiein Germany, Montecatini in Italy, and Dow Chemical, Du Pont, Esso (later Exxon andmore recently Exxon Mobil), Hercules, Koppers, and others in the United States. Koppersbegan a semi-works plant in the United States in 1956, and Hercules a full scale plant in1957.

1.2.3 Standard Oil of Indiana

At this time, various industrial companies were involved in trying to polymerize ethylene.Zletz [23] of Standard Oil of Indiana (later Amoco and subsequently BP Amoco)described in an April 1951 patent application of the polymerization of ethylene withmolybdenum oxide-aluminum oxide initiators. Compounds such as cobalt-molybdatewere probably involved. Products from greases to tough resins were produced, but littleinformation, if any, was given in the patent about the structure of the resin. It appearsto have been a linear polyethylene. These activities were only slowly followed up.

1.2.4 Phillips Petroleum and High Density Polyethylene

In the 1940s, Bailey and Reid [24] of Phillips Petroleum (later Conoco Phillips) in Bartles-ville, Oklahoma, USA found that ethylene could be polymerized to liquid polymersover certain nickel oxide-silica-alumina catalysts. Subsequently, Hogan and Banks [25]

1.2 Polyethylene

6 1 Origins of Polyolefins [Refs. on p. 19]

building on this work polymerized ethylene to solid polymers using chromium oxide-silica-alumina catalysts. Chromium oxide with zirconium oxide and thorium oxide werealso discussed. The polymerization product was proved to be a linear high densitypolyethylene [25, 26]. Phillips filed a patent application on January 24, 1953 [25]. Laterpatents by Hogan and Banks [27, 28] describe initiators based on chromium oxide andstrontium oxide [27] and chromium oxide with various additives [28].

Applications research and market development began in 1955. A 1000 lbs (0.5 ton) perday semiworks plant was put into operation in Bartlesville [29]. In April 1955, PhillipsPetroleum approved the building of a polyethylene plant in Pasadena, Texas with aproduction capacity of 6.5 million lbs per month [29]. Phillips Petroleum moved intocommercial production of high density polyethylene in 1956 [29].

Licenses were given in 1955–1956 to nine different companies in seven countries toproduce high density polyethylene according to the Phillips process.

A 1956 paper by Jones and Boeke [30] describes the new Phillips Marlex® 50 polyethylenewith a density of 0.96 g/cm3 as opposed to 0.92 g/cm3 for conventional high pressurebranched polyethylene and a melting point of 135 °C as opposed to 110 °C.

By this time, the older ICI type polyethylene was becoming called low density poly-ethylene (LDPE), and the newer materials made by Ziegler and Phillips catalysts werecalled high density polyethylene (HDPE).

1.2.5 Linear Low Density Polyethylene

Phillips Petroleum seems to have begun research on ethylene copolymers quite early,and they are cited in the original Hogan and Banks patent [25]. By 1958, Phillips wascommercially manufacturing high to moderate density ethylene-butene copolymers.

As early as 1957, DuPont researchers filed patents [31, 32] on copolymers of ethylenewith varying amounts of 1-butene, 1-pentene, 1-hexene, 1-octene, and higher α-poly-olefins such as 1-decene and 1-octadecene with a Ziegler type catalyst. These newcopolymers had densities similar to the ICI LDPE (~0.92 g/cm3). The best mechanicaland optical performance in the copolymers was found for the higher olefin comonomersincluding 1-octene, 1-decene, and higher α-olefins. DuPont researchers considered alsoa terpolymer with ethylene and two minor monomers, one a higher olefin such as octeneand the other a lower olefin such as propylene.

These new polymers were called linear low density polyethylene (LLDPE) to distinguishthem from LDPE. Crystallinity reduction came from the comonomers.

7

Phillips Petroleum began to manufacture ethylene-hexene copolymers with densitiesof 0.92 g/cm3 in 1968. Linear low density polyethylene was developed widely commer-cially in the 1970s, notably by a process technology developed by Union Carbide.

LLDPE has come to increasingly supplant the ICI type LDPE.

1.3 Isotactic Polypropylene

1.3.1 Giulio Natta, Milan Politechnico and Montecatini

Natta had research assistants in Ziegler’s Mülheim laboratory from 1950 and becamevery familiar with his polymerization systems [18]. He was aware that Ziegler had triedto polymerize polypropylene but had not considered it successful. In 1953–1954, Zieglersold pails of his catalysts to various industrial firms. Among those obtaining catalystswas the Montecatini company based in Milan, Italy. Montecatini made arrangementswith Prof. Giulio Natta and his coworkers to apply these catalysts to a range of monomers.Natta, on receiving the catalysts, immediately turned his attention to polypropylene.

Natta et al. made rapid progress with polypropylene.

CH2-CH

CH3

*CH2-CH

CH3

* (1-III)

Polypropylene with its asymmetric carbon atoms (C*) was known at the time as arubbery waxy non-crystalline material. The new discoveries were quite striking.Staudinger [2] in his 1932 monograph had noted the occurrence of the large numberof stereoisomeric groups in polymers due to asymmetric carbon atoms in polystyreneand other vinyl polymers. In 1942, Bunn [33] with ICI had imagined stereoregularvinyl chains and sought to predict their structures in crystals. The early Natta poly-propylenes prepared were rubbery and waxy but contained hard white materials [18],which were found to be crystalline. The first crystalline polypropylenes were synthesizedby Natta et al. in March 1954. Further X-ray diffraction investigations and model builtby Natta and Corradini showed that all of the asymmetric carbon atoms had the samesymmetry. The new polypropylene was called ‘isotactic’ (roughly same placement)following the suggestion of Natta’s wife (see Section 2.2.2). The isotactic polypropylenechain structure was the same as the one proposed by Bunn [33].

1.3 Isotactic Polypropylene

8 1 Origins of Polyolefins [Refs. on p. 19]

Natta together with P. Pino and G. Mazzanti began filing patents [34] in June 1954.They claimed a stereoregular crystalline polypropylene polymerized by Ziegler typecatalysts. The examples include initiator systems

• aluminum triakyl-titanium tetrachloride,

• aluminum trialkyl-titanium tetrabromide,

• aluminum trialkyl-vanadium tetrachloride,

• aluminum trialkyl-zirconium tetrachloride, and

• aluminum trialkyl-chromium acetylacetonate.

The US patent, which did not issue until 1973 was assigned to Montecatini Edison, thesuccessor company of Montecatini.

Ironically, Ziegler soon synthesized a crystalline polypropylene with his catalyst.However, when he discovered the Natta-Pino-Mazzanti patent application, he withdrewhis claim and supported Natta.

In 1954–1955, Natta and his coworkers [35–37] submitted a series of papers in whichthey announced the synthesis of the new crystalline polypropylene. It had a density of0.91 g/cm3 and a crystalline melting temperature of about 165 °C.

Production of isotactic polypropylene was initiated by Montecatini in Brindisi, Italy in1957. Farbwerke Hoechst and Hercules began production of isotactic polypropylenewith Montecatini licenses in 1957 and 1958. It has since become the world’s majorthermoplastic second only to polyethylene. Hercules and Montecatini later merged theiroperations to form Himont. This company in turn joined with Shell to form Montell.BASF later joined this combine to form Basell.

There was a long period of catalyst development and improvement to make isotacticpolypropylene. The problem was to achieve both high yield and high tacticity [38, 39].This has involved various generations of what may be called Ziegler-Natta catalysts.

1.3.2 Standard Oil of Indiana and Phillips Petroleum

Researchers at Standard Oil of Indiana (now BP Amoco) and Phillips Petroleum (nowConoco Phillips) were also trying to synthesize polypropylene. In the end, this wouldlead to long complex legal suits. Pino and Moretti [40] indicated that D. R. Carmody inStandard Oil of Indiana may have synthesized isotactic polypropylene as early as 1950

9

but only characterized the product with infrared spectroscopy. However, knowledge ofinfrared spectroscopy at that time was insufficient to describe tacticity.

Phillips Petroleum [25, 26] also sought to polymerize propylene monomer. Accordingto Pino and Moretti [40], E. Francis may have made isotactic polypropylene as early as1951. Like Standard Oil of Indiana, Phillips Petroleum only characterized their newpolypropylene with infrared spectroscopy and did not elucidate what it was. Synthesisof polypropylene is described in the first Hogan and Banks patent [25] filed in January1953. Little is said of the characteristics of the polypropylene in the patent, and nothingis said of stereoregularity.

1.4 Isotactic Polybutene-1

Natta et al. [35–37] investigated the polymerization of 1-butene in the same period astheir studies of polypropylene. They succeeded in producing isotactic polybutene-1,that is

CH2-CH

CH2

*

CH3

CH2-CH

CH2CH2

*

CH3CH3

(1-IV)

in 1954 and determined its crystal structure to prove its stereoregularity. It wascharacterized by peculiar polymorphic characteristics in which it would initiallycrystallize into one form (Form II) and then, within hours, recrystallize into a secondform (Form I).

The polymerization of polybutene-1 is also described in the Hogan and Banks patent[25]. Little detail about its characteristics is given.

Petrotex Corp. began commercial development of isotactic polybutene-1 in 1963 witha 2000 lbs/day semiworks plant [26]. It was operated until 1966 and then abandoned asunpromising. In 1967, Mobil Corp. started up a plant in Texas with a capacity of 4 millionlbs per year. In 1972, Mobil decided not to continue and licensed its technology toWitco Chemical. Witco then built a plant in Louisiana 50 with a capacity of million lbsper year. In 1977, the plant was sold to Shell [26]. Today this plant is operated by Basell.

1.4 Isotactic Polybutene-1

10 1 Origins of Polyolefins [Refs. on p. 19]

1.5 Isotactic Polymers of Higher Olefins andPoly(4-Methyl Pentene-1)

Natta et al. [37] followed up the polymerization of isotactic polypropylene and isotacticpolybutene-1 with the synthesis of higher isotactic α-polyolefins. The polymerssynthesized and their crystalline melting temperatures are listed in Table 1.1 [41]. Thesepossess the structural unit

CH2-CH

(CH2)n

*

CH3

CH2-CH

(CH2)n

*

CH3CH3

(1-V)

which contains an asymmetric carbon atom in each repeat unit. As n (the number ofCH2 units in the pending substituent) increases, the crystalline melting temperaturedecreases from 165 °C (n = 0) to 125 °C for n = 1, to 70 °C for n = 2 and to –55 °C forn = 3. Table 1.1 summarizes crystalline melting temperatures for this series whichindicate that this was not a promising direction.

Natta and his coworkers now looked at branched polyolefins to achieve higher meltingtemperatures [37]. The monomers considered include

CH2=CH-CH-CH3

CH3

CH2=CH-CH-CH3

CH3

CH2=CH-CH2-CH-CH3

CH3

CH2=CH-CH2-CH-CH3

CH3

(1-VI)CH2=CH-CH-CH2-CH3

CH3

CH2=CH-CH-CH2-CH3

CH3

CH2=CH-CH2-CH2-CH-CH3

CH3

CH2=CH-CH2-CH2-CH-CH3

CH3

Table 1.1 Melting Temperatures of Polyethylene and Isotactic Polymers of α-Olefins [41]

Polymer Tm

(°C)

Polyethylene Polypropylene Polybutene-1 Polypentene-1 Polyhexene-1 Polyheptene-1 Polyoctene-1 Polydodecene-1 Polyoctadecene-1

135 165 128 70 –55 –40 –38 45 70

11

The melting temperatures of isotactic polymers of all these monomers are higher thanthe one of isotactic polypropylene. The melting temperature of poly(3-methyl butene-1)was too high for it to be successfully processed. Poly(4-methyl pentene-1) had a meltingtemperature of about 235 °C and attracted the most attention. The polymer was alsoremarkable for its transparency, because the crystalline density was close to its amorphousdensity. However, it has a β-transition or glass transition of about 16 °C. This leads toproblems with mechanical behavior at room temperature.

It should be noted that poly(4-methyl pentene-1) was also synthesized by Hogan andBanks in their patents, but little was said of its characteristics.

ICI started the commercial development of poly(4-methyl pentene-1) in 1965, and aplant with a capacity of 4.5 million lbs/year was built in 1968. Various papers on itscharacteristics were published [42–44]. ICI later licensed the technology to MitsuiPetrochemical, which has been its primary manufacturer since 1975. Phillips Petroleummanufactured this polymer for a short time in the 1990s.

1.6 Ethylene-Propylene Rubber

Early patents such as Zletz [23] and Hogan and Banks [25] discuss copolymerization ofethylene with other olefinic monomers such as propylene. However, the products arenot discussed as materials. A 1955 patent application [45] by Natta with G. Mazzantiand G. Buschi describes the synthesis of elastomeric copolymers of ethylene withpropylene, butene-1, pentene-1, and hexene-1. Typical polymerization initiators werealuminum trialkyl with VOCl3. The patent was assigned to Montecatini.

Ethylene-propylene rubber was commercially produced in the late 1950s. The weaknessof this product was that it could not be vulcanized. This was resolved by introducing athird monomer with two double bonds of unequal reactivity. Here, the more reactivedouble bonds are incorporated in the polymerization. The second double bond is usedfor vulcanization. The two major monomers that came to be used in small amountswith ethylene and propylene were

CH-CH3

CH2=CH-CH2-CH=CH-CH3

ethylidene norbornene 1,4-hexadiene

CH-CH3CH-CH3

CH2=CH-CH2-CH=CH-CH3

ethylidene norbornene 1,4-hexadiene

(1-VII)

1.6 Ethylene-Propylene Rubber

12 1 Origins of Polyolefins [Refs. on p. 19]

Major manufacturers of ethylene-propylene terpolymers today include DuPont-Dow,Exxon Mobil, and Uniroyal Chemical.

1.7 Metallocene Polymerization

Since Ziegler’s announcement of polyethylene, chemists and industrial firms around theworld sought to modify and improve his polymerization initiator system. Simmonazziand Giannini [38] and Albizzati et al. [39] described the Montecatini-Himont effortsto improve Ziegler-Natta catalyst/initiator systems. The latter authors suggested thatthere have been six generations of catalysts related to isotactic polypropylene.

By the late 1970s, attention turned to systems such as [46]:

AlR2Cl TiCp2Cl2 (1-VIII)

where R is an alkyl group, and Cp is cyclopentadiene. Addition of water to the aluminumalkyl co-initiator converted it to complex aluminoxanes, which increased the catalystactivity substantially. If aluminum trimethyl is used, methyl aluminoxane, which hasthe following structure

(CH3)2 [ O-Al ] (CH3)2

CH3

(CH3)2 [ O-Al ] (CH3)2

CH3

(1-IX)

is formed. This has an especially high reactivity. Typical metallocene initiators involveit in combination with structures such as

MCp

Cp XXMCp

Cp XX

or MX

XR R

RR

MX

XR R

RR

(1-X)

where X is Cl or halogen, and R is H or alkyl. The metal M is usually Zr, Ti or Hf. Thedashed line represents an optional bridge.

The development of this catalyst system can be followed through the work beginningwith Ziegler et al. [21] to Natta et al. [34], Breslow and Newburg [47], Sinn et al. [48],

13

Ewen [49], and Kaminsky et al. [50]. Albizzatti et al. [39] call the metallocene catalysts‘6th generation’ stereospecific catalysts.

The metallocene catalysts proved able to produce highly stereoregular syndiotacticpolyolefins. They have also been able to produce polyolefins with specific microstructurelevels. The polymers synthesized had narrow molecular weight distributions.

These polymerization initiators have been developed by Dow Chemical, Exxon (laterExxon Mobil), Idemitsu Kosan, and others to develop new families of polyolefins andcopolymers.

1.8 Stereoregular Polystyrenes

1.8.1 Isotactic Polystyrene

Atactic polystyrene, that is

CH2-CHCH2-CH (1-XI)

has long been known. It is an amorphous thermoplastic with a glass transitiontemperature of approx. 100 °C. It was first commercialized in the 1930s by the I. G.Farbenindustrie.

Isotactic polystyrene was one of the first polymers synthesized by Natta and his coworkers[51] in 1954–1955. It had a crystalline melting temperature of approx. 230 °C and wasinvestigated by various industrial firms from the 1950s to the 1970s, but none decidedto commercialize it. A major reason often cited was its slow crystallization rate.

1.8.2 Syndiotactic Polystyrene

Syndiotactic polystyrene was developed by Ishihara and his coworkers [52, 53] withIdemitsu Kosan in the mid 1980s using metallocene initiators. It has a crystalline meltingtemperature of approx. 270 °C. The material is being commercially developed byIdemitsu and Dow Chemical.

1.8 Stereoregular Polystyrenes

14 1 Origins of Polyolefins [Refs. on p. 19]

1.9 Syndiotactic Polypropylene

Syndiotactic polypropylene is another stereoregular form of polypropylene. It has acrystalline melting temperature of approx. 155 °C (in highly stereoregular polymers).The synthesis of syndiotactic polypropylene was first reported by Natta and his coworkers[54, 55] in 1960–1962.

The early-stage syndiotactic polypropylenes produced using vanadium-based Ziegler-Natta catalysts contained significant amounts of isotactic segment blocks and stereo-irregularities. This led to low syndiotacticity levels (usually 60 to 70% syndiotactictetrads) and poor mechanical and thermal properties. In more recent years, newmetallocene catalysts allowed major improvements in syndiotactic polypropylene.It became commercially available in the 1990s. Fina Oil and its successor AtoFinaPetrochemicals brought syndiotactic polypropylene to the market place.

1.10 Cyclopolyolefins

The polymerization of norbornene

(1-XII)

was first described in the late 1950s by DuPont researchers [56–58]. They used a Ziegler-type lithium aluminum trialkyl-titanium tetrachloride catalyst. The polymer synthesizedhad the structure

CH=CHCH=CH(1-XIII)

In March 1964, a patent application by McKeon and Starcher [59] of Union Carbidedescribed the polymerization of norbornene with palladium compounds leading tothe structural unit

(1-XIV)