ch 02

i

Polyolefin fibres

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The Textile Institute and Woodhead Publishing
The Textile Institute is a unique organisation in textiles, clothing and footwear.
Incorporated in England by a Royal Charter granted in 1925, the Institute
has individual and corporate members in over 90 countries. The aim of the
Institute is to facilitate learning, recognise achievement, reward excellence
and disseminate information within the global textiles, clothing and footwear
industries.
Historically, The Textile Institute has published books of interest to its
members and the textile industry. To maintain this policy, the Institute has
entered into partnership with Woodhead Publishing Limited to ensure that
Institute members and the textile industry continue to have access to high
calibre titles on textile science and technology.
Most Woodhead titles on textiles are now published in collaboration with
The Textile Institute. Through this arrangement, the Institute provides an
Editorial Board which advises Woodhead on appropriate titles for future
publication and suggests possible editors and authors for these books. Each
book published under this arrangement carries the Institute’s logo.
Woodhead books published in collaboration with The Textile Institute are
offered to Textile Institute members at a substantial discount. These books,
together with those published by The Textile Institute that are still in print,
are offered on the Woodhead website at: www.woodheadpublishing.com.

Textile Institute books still in print are also available directly from the Institute’s
website at: www.textileinstitutebooks.com.
A list of Woodhead books on textile science and technology, most of
which have been published in collaboration with The Textile Institute, can be
found on pages xiii–xvii.

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iii

Woodhead Publishing in Textiles: Number 82

Polyolefin fibres
Industrial and medical
applications
Edited by
Samuel C. O. Ugbolue

CRC Press
Boca Raton Boston New York Washington, DC

WOODHEAD

PUBLISHING LIMITED
Cambridge

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New Delhi

iv
Published by Woodhead Publishing Limited in association with The Textile Institute
Woodhead Publishing Limited, Abington Hall, Granta Park, Great Abington
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First published 2009, Woodhead Publishing Limited and CRC Press LLC
© Woodhead Publishing Limited, 2009
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Contents

Contributor contact details

xi

Woodhead Publishing in Textiles

xiii

Preface

xix

Part I Properties and applications of polyolefin fibres
1

Types of polyolefin fibres

3

A CRANGLE, Formerly of University of Ulster at Belfast, UK

1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
1.10
1.11
1.12
1.13
1.14
1.15
1.16

Introduction
Definitions of polymers, fibres and polyolefins
Chemistry of alkene (olefin) monomers
Polymers and polymerisation reactions
Stereochemistry and the structure of polyolefins
Polyethylene fibres
Polypropylene fibres
Polyolefin fibres from copolymers
Polyolefin fibres from polymer blends or alloys
Polyolefin bi-component fibres
Polyolefin nanocomposite fibres
Classification of polyolefin fibres and textiles
Future trends
Conclusions
Sources of further information and advice
References

3
4
5
6
9
15
16
19
20
23
24
25
26

28
29
30

2

The structural and chemical properties of polyolefin
fibres

35

R R MATHER, Heriot-Watt University, UK

2.1

Introduction

35

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Contents

2.2
2.3
2.4
2.5

2.6
2.7
2.8
2.9

Arrangement of polyolefin chains
Crystalline structures
Crystal morphology
Chemical properties
Oxidation of polyolefin fibres
Stabilisers
Surface chemistry of polyolefin fibres
References

37
38
40
41
42
45
50
54

3

The structural mechanics of polyolefin fibrous
materials and nanocomposites

57

S UGBOLUE, University of Massachusetts, USA

3.1
3.2
3.3
3.4
3.5
3.6
3.7
3.8
4

Introduction
The structure and mechanics of polyolefin fibrous
materials
The mechanical properties of polyolefin fibers and films
Characterization of polyolefin fibrous materials and
nanocomposites
Structure-property improvements of polyolefin
nanocomposites
Conclusions
Acknowledgements
References
Automotive components composed of polyolefins

57
58
59
66
70

78
78
79
81

E SADIKU, Tshwane University of Technology, Republic of
South Africa

4.1
4.2
4.3
4.4
4.5
4.6
4.7
4.8
4.9
4.10
4.11
4.12

Introduction: brief survey of polyolefin resins and their
general properties
Types of polyolefins
Ethylene copolymers
Polypropylene (PP) and its composites
Polyolefin-based nanocomposites
Foamable and expandable polyolefins (FEPO)
Sun visors
Ethylene propylene rubbers: ethylene propylene diene

(EPDM) and ethylene propylene copolymers (EPM)
Other poly (α-olefins)
Cyclo-olefin copolymers: properties and applications
Polyolefin elastomers: properties and applications of
polyolefin elastomers (POE)
Chlorinated polyethylene and chloro-sulphonated
polyethylene

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84
90
91
98
100
105
106
107
108
108
109


Contents

4.13
4.14
4.15
4.16

4.17
4.18
5

vii

Thermoplastic elastomers (TPEs)
Specific automotive components made of
polyolefin-based materials
Future trends
Conclusions
Sources of further information and advice
References

109
119
126
127
128
129

The use of polyolefins in industrial and medical
applications

133

Y KIM, University of Massachusetts, USA

5.1
5.2

5.3
5.4
5.5
5.6
5.7

Introduction
Technical textile applications of polyolefins
Polyolefin fiber properties and types
Technical fibrous structures from polyolefin fibers
Industrial applications of polyolefin fibers
Conclusions and future trends
References

133
135
136
138
144
151
152

6

Advances in polyolefin-based fibers for hygienic and
medical applications

154

R M PATEL and J MARTIN, The Dow Chemical Company, USA and

G CLAASEN and T ALLGEUER, Dow Plastics, Switzerland

6.1
6.2
6.3
6.4
6.5
6.6
6.7

Introduction
Monocomponent polyethylene-based soft spunbond
fabrics
Monocomponent polypropylene-based soft spunbond
fabrics
Bi-component spunbond fabric and bi-component binder
fibers
Conclusions
Acknowledgements
References

154
156
168
171
180
181
181

Part II Improving the functionality of polyolefins

7

Production methods for polyolefin fibers

185

R KOTEK, M AFSHARI, V HARBISON and A GUPTA, North Carolina
State University, USA

7.1
7.2
7.3

Introduction
Manufacturing of polyolefins
Melt spinning of polypropylene

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186
206


viii

Contents

7.4
7.5

7.6
7.7

Important factors in melt spinning of polypropylene
Melt spinning of polyethylene
Other production methods for polyolefins
References

219
245
247
258

8

Enhancing hygiene/antimicrobial properties of
polyolefins

262

M BADROSSAMAY and G SUN, University of California, USA

8.1
8.2
8.3
8.4
8.5
9

Introduction

Antimicrobial functions
Antimicrobial polyolefins
Future trends
References

262
263
265
281
283

Improving the use of polyolefins in nonwovens

288

S R MALKAN, Hunter Douglas, USA

9.1
9.2
9.3
9.4
9.5
9.6
9.7
9.8
9.9
9.10
10

Introduction

Nonwoven definition
Nonwoven market
Classification of nonwoven fabrics
Finishing of nonwovens
Characteristics and properties of nonwoven fabrics
Consumption profile of polyolefins in nonwovens
Applications of polyolefin nonwovens
Future trends
References

288
289
291
291
302
304
305
312
313
314

Testing and quality control of polyolefins

316

S UGBOLUE, University of Massachusetts, USA

10.1
10.2
10.3

10.4
10.5
10.6
11

Introduction
Testing and characterization of polyolefins
Selected product analysis and performance evaluation:
case study on polyolefin nanocomposites
Quality control considerations
Acknowledgements
References

316
318
330
339
339
339

Polyolefin nanocomposite fibers and films

341

Q FAN, University of Massachusetts, USA

11.1
11.2
11.3

Introduction
Polyolefin nanocomposite fibers and films
Preparation of polyolefin nanocomposite fibers and films

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342
345


Contents

ix

11.4
11.5
11.6
11.7
11.8
11.9

Characterization and analysis
Applications of polyolefin nanocomposites
Chemical applications
Conclusions
Acknowledgements
References

346

351
353
357
358
358

12

Improving the colouration/dyeability of polyolefin
fibres

363

R SHAMEY, North Carolina State University, USA

12.1
12.2
12.3
12.4
12.5
12.6
12.7
12.8
12.9

Introduction
Overview of structural features of polyolefins
An overview of dye–fibre interactions
Colorants
Colouration of unmodified polyolefins

Improving colouration of polypropylene through fibre
modification
Conclusions
Acknowledgements
References

384
391
392
392

Index

398

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363
364
366
368
369


x

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xi

Contributor contact details

(* = main contact)

Editor

Chapters 3 and 10

Professor Samuel C. O. Ugbolue
Department of Materials and
Textiles
University of Massachusetts
Dartmouth, MA 02747
USA

Professor Samuel C. O. Ugbolue
Department of Materials and
Textiles
University of Massachusetts
Dartmouth, MA 02747
USA

E-mail:

E-mail:

Chapter 1

Chapter 4

Dr A. Crangle
59 Rutherglen Street
Belfast BT13 3LR
UK

Professor E. R. Sadiku
Tshwane University of Technology
Faculty of Engineering
Department of Polymer Technology
CSIR Campus, Building 14D
Postnet Suit #186, P/Bag X025
Lynnwoodridge 0040
Republic of South Africa

Email:


Chapter 2

E-mail:

Dr R. R. Mather
School of Engineering and Physical
Sciences
Heriot-Watt University
Riccarton
Edinburgh EH14 4AS
UK
E-mail:

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xii

Contributor contact details

Chapter 5

Chapter 8

Professor Y. K. Kim
Department of Materials and
Textiles
College of Engineering
University of Massachusetts
Dartmouth, MA 02747
USA

Professor G. Sun* and M. R.
Badrossamay
Division of Textiles and Clothing
University of California, Davis
Davis, CA
USA
E-mail:

E-mail:

Chapter 9
Chapter 6
Dr R. M. Patel* and J. Martin
The Dow Chemical Company
Freeport, TX 77541
USA

Dr S. R. Malkan
Hunter Douglas
1 Duette Way
Broomfield, CO 80020
USA

E-mail:

E-mail:

G. Claasen and T. Allgeuer
Dow Plastics
Horgen
Switzerland

Chapter 11

Chapter 7
Dr R. Kotek*, M. Afshari,
V. Harbison and A. Gupta
College of Textiles
North Carolina State University
Raleigh, NC 27695-8301

USA
E-mail:

Qinguo Fan
Department of Materials and
Textiles
University of Massachusetts
Dartmouth, MA 02747
USA
E-mail:

Chapter 12
Dr R. Shamey
Associate Professor in Polymer and
Color Chemistry
College of Textiles
North Carolina State University
Raleigh, NC 27695-8301
USA
E-mail:

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xiii

Woodhead Publishing in Textiles

1 Watson’s textile design and colour Seventh edition
Edited by Z. Grosicki

2 Watson’s advanced textile design
Edited by Z. Grosicki
3 Weaving Second edition
P. R. Lord and M. H. Mohamed
4 Handbook of textile fibres Vol 1: Natural fibres
J. Gordon Cook
5 Handbook of textile fibres Vol 2: Man-made fibres
J. Gordon Cook
6 Recycling textile and plastic waste
Edited by A. R. Horrocks
7 New fibers Second edition
T. Hongu and G. O. Phillips
8 Atlas of fibre fracture and damage to textiles Second edition
J. W. S. Hearle, B. Lomas and W. D. Cooke
9 Ecotextile ’98
Edited by A. R. Horrocks
10 Physical testing of textiles
B. P. Saville
11 Geometric symmetry in patterns and tilings
C. E. Horne
12 Handbook of technical textiles
Edited by A. R. Horrocks and S. C. Anand
13 Textiles in automotive engineering
W. Fung and J. M. Hardcastle

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Woodhead Publishing in Textiles

14 Handbook of textile design
J. Wilson
15 High-performance fibres
Edited by J. W. S. Hearle
16 Knitting technology Third edition
D. J. Spencer
17 Medical textiles
Edited by S. C. Anand
18 Regenerated cellulose fibres
Edited by C. Woodings
19 Silk, mohair, cashmere and other luxury fibres
Edited by R. R. Franck
20 Smart fibres, fabrics and clothing
Edited by X. M. Tao
21 Yarn texturing technology
J. W. S. Hearle, L. Hollick and D. K. Wilson
22 Encyclopedia of textile finishing
H-K. Rouette
23 Coated and laminated textiles
W. Fung
24 Fancy yarns
R. H. Gong and R. M. Wright
25 Wool: Science and technology
Edited by W. S. Simpson and G. Crawshaw
26 Dictionary of textile finishing
H-K. Rouette
27 Environmental impact of textiles
K. Slater

28 Handbook of yarn production
P. R. Lord
29 Textile processing with enzymes
Edited by A. Cavaco-Paulo and G. Gübitz
30 The China and Hong Kong denim industry
Y. Li, L. Yao and K. W. Yeung
31 The World Trade Organization and international denim trading
Y. Li, Y. Shen, L. Yao and E. Newton

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xv

32 Chemical finishing of textiles
W. D. Schindler and P. J. Hauser
33 Clothing appearance and fit
J. Fan, W. Yu and L. Hunter
34 Handbook of fibre rope technology
H. A. McKenna, J. W. S. Hearle and N. O’Hear
35 Structure and mechanics of woven fabrics
J. Hu
36 Synthetic fibres: nylon, polyester, acrylic, polyolefin
Edited by J. E. McIntyre
37 Woollen and worsted woven fabric design
E. G. Gilligan
38 Analytical electrochemistry in textiles
P. Westbroek, G. Priniotakis and P. Kiekens

39 Bast and other plant fibres
R. R. Franck
40 Chemical testing of textiles
Edited by Q. Fan
41 Design and manufacture of textile composites
Edited by A. C. Long
42 Effect of mechanical and physical properties on fabric hand
Edited by Hassan M. Behery
43 New millennium fibers
T. Hongu, M. Takigami and G. O. Phillips
44 Textiles for protection
Edited by R. A. Scott
45 Textiles in sport
Edited by R. Shishoo
46 Wearable electronics and photonics
Edited by X. M. Tao
47 Biodegradable and sustainable fibres
Edited by R. S. Blackburn
48 Medical textiles and biomaterials for healthcare
Edited by S. C. Anand, M. Miraftab, S. Rajendran and J. F. Kennedy
49 Total colour management in textiles
Edited by J. Xin

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Woodhead Publishing in Textiles

50 Recycling in textiles
Edited by Y. Wang
51 Clothing biosensory engineering
Y. Li and A. S. W. Wong
52 Biomechanical engineering of textiles and clothing
Edited by Y. Li and D. X-Q. Dai
53 Digital printing of textiles
Edited by H. Ujiie
54 Intelligent textiles and clothing
Edited by H. Mattila
55 Innovation and technology of women’s intimate apparel
W. Yu, J. Fan, S. C. Harlock and S. P. Ng
56 Thermal and moisture transport in fibrous materials
Edited by N. Pan and P. Gibson
57 Geosynthetics in civil engineering
Edited by R. W. Sarsby
58 Handbook of nonwovens
Edited by S. Russell
59 Cotton: Science and technology
Edited by S. Gordon and Y-L. Hsieh
60 Ecotextiles
Edited by M. Miraftab and A. Horrocks
61 Composite forming technologies
Edited by A. C. Long
62 Plasma technology for textiles
Edited by R. Shishoo
63 Smart textiles for medicine and healthcare
Edited by L. Van Langenhove
64 Sizing in clothing
Edited by S. Ashdown

65 Shape memory polymers and textiles
J. Hu
66 Environmental aspects of textile dyeing
Edited by R. Christie
67 Nanofibers and nanotechnology in textiles
Edited by P. Brown and K. Stevens

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Woodhead Publishing in Textiles

xvii

68 Physical properties of textile fibres Fourth edition
W. E. Morton and J. W. S. Hearle
69 Advances in apparel production
Edited by C. Fairhurst
70 Advances in fire retardant materials
Edited by A. R. Horrocks and D. Price
71 Polyesters and polyamides
Edited by B. L. Deopura, R. Alagirusamy, M. Joshi and B. S. Gupta
72 Advances in wool technology
Edited by N. A. G. Johnson and I. Russell
73 Military textiles
Edited by E. Wilusz
74 3-D fibrous assemblies: Properties, applications and modelling of
three-dimensional textile structures
J. Hu
75 Medical textiles 2007

Edited by J. Kennedy, A. Anand, M. Miraftab and S. Rajendran
(forthcoming)
76 Fabric testing
Edited by J. Hu
77 Biologically inspired textiles
Edited by A. Abbott and M. Ellison
78 Friction in textiles
Edited by B .S. Gupta
79 Textile advances in the automotive industry
Edited by R. Shishoo
80 Structure and mechanics of textile fibre assemblies
Edited by P. Schwartz
81 Engineering textiles: Integrating the design and manufacture of
textile products
Edited by Y. E. El-Mogahzy
82 Polyolefin fibres: Industrial and medical applications
Edited by S. C. O. Ugbolue

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xviii

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xix

Preface

In spite of the advances made in polymer science and engineering, particularly
in the important fields of nanocomposites and biomaterials, the importance
of polyolefins remains very strong. Polyethylene and polypropylene are very
important polyolefin polymers and the fastest growing polymer family.
Polyolefins cost less to produce and process than many other plastics and
materials they replace. Indeed, polypropylene (PP) is a versatile and widely
used synthetic polymer for hygienic applications such as food packaging,
surgical masks, diapers(nappies), hygiene bands, filters, automotive parts,
etc. Polyolefins are also important for fibers and films; polypropylene fibers
are used widely in upholstery fabrics, geotextiles and carpet backing. Evidently,
because of the low cost, high strength, high toughness and resistance to
chemicals, polypropylene fibers find a broad spectrum of use in the industrial
and home furnishing sectors and medical applications. Thus, our knowledge
in engineering nanocomposite polyolefin materials has proved invaluable in
improving the range of commercially available products. However, PP fibers
do not enjoy comparable popularity in the apparel sector of the textile industry;
one of the main reasons is lack of dyeability.
This book contains recent information and research data on the subject. It
is a significant contribution to our further understanding of the properties
and applications of polyolefin fibers as expressed by the authors of the
various topics that comprise the chapters in Part I. In Part II of the book, the
focus is on issues dealing with improving the functionality of polyolefins,
such as enhancing hygiene/antimicrobial properties of polyolefins, improving
the use of polyolefins in nonwovens, testing and quality control of polyolefins
and improving the colouration/dyeability of polyolefin fibers.
I am most grateful to all the contributors for their time, determination and
enthusiasm in insuring that the deadline of the editorial team was met. I am
indebted to all the members of my family for their support, interest and
encouragement in the realization of this book project. Many of my graduate
students and visiting scientists from various universities across the globe

have made contributions through our shared research projects over the years
and their efforts are duly acknowledged.

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Preface

I believe this book provides excellent information not only for researchers,
academics and professionals in the biomaterials, nonwoven and medical
areas but also for technologists, engineers, product designers, marketers and
managers in the polymer, textile and allied industries.
S. C. O. Ugbolue
UMassDartmouth

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1
Types of polyolefin fibres
A C R A N G L E, Formerly of University of Ulster at Belfast, UK

Abstract: This chapter discusses the chemistry of olefin monomers, their
role in stereospecific addition polymerisation, the chain conformation or
tacticity of resultant polymers and the influence of macromolecular structure
on the physical characteristics of polyethylene, polypropylene and other
alpha polyolefins, when used as textile materials. The characteristics of other
polyolefin fibres produced from olefin copolymers or miscible blends and

bicomponent filament structures are reported. Polyolefin textiles are
classified in terms of their structure and chemical nomenclature, fibre
processing technology or application of the textile material. The progressive
commercial introduction of polyolefins fibres and textiles and future trends
is reviewed.
Key words: chemistry of olefin monomers, chain conformation or tacticity,
polyolefin textiles are classified, structure and chemical nomenclature,
polyolefin fibres and textiles.

1.1

Introduction

Polyolefin polymers and the resultant textiles made therefrom have, over the
last 50 years or so, progressively replaced both natural and other man-made
fibres in many day-to-day applications. In addition, they have consistently
been the polymeric textile of choice for many progressive and innovative
textile developments and applications that, in 2007, are generally taken for
granted by the general public. The European Association of Textile Polyolefins
(EATP) eloquently describes polyolefin textiles in the following manner
(Anon., 2007f):
In homes and automobiles, clothing and carpeting, health care and industry,
polyolefin is quietly at work in thousands of applications around the
world. This versatile, high-tech fibre is durable, colourfast and chemically
resistant, yet economical and environmentally friendly. Polyolefin
consistently outperforms other fibre materials. From its discovery in 1954
by Nobel prize-winning chemist Giulio Natta, polypropylene has proven
that it is a hard-working polymer.
Polyolefin plastics and fibres keep our carpeting clean and transport
moisture away from the body to keep our active wear dry. They protect

sterile environments and soak up industrial spills. PP is literally ‘on the
job’ in our homes, cars and businesses, each and every day.
3

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4

Polyolefin fibres

Whilst the main topic of this chapter is ‘Types of polyolefins’, it is the
author’s opinion that it is important to understand some of the basics relating
to the chemistry of alkenes (alpha olefin monomers), and, in particular, how
the stereochemistry of these basic polymer building blocks has an important
part to play with respect to addition polymerisation at a catalyst surface and,
subsequently, on the physical characteristics of the bulk polymeric material.
The commercially important polyolefin fibres, polypropylene and
polyethylene, are discussed in terms of their basic structure. A brief review
of their development and commercial introduction is also included. The
other poly (alpha olefins) are discussed in terms of their use as fibrous
materials. Polyolefin fibres produced from copolymers or blends or as bicomponent fibrous materials are reviewed. To accommodate the various
aspects of the polyolefin textiles industry, classification has been dealt with
in terms of the structure/chemical nomenclature of the polymer, the fibre
processing technology or the application of the textile material. A brief survey
of possible future trends followed by conclusions and sources of further
reading complete the chapter.

1.2

Definitions of polymers, fibres and polyolefins

A polymer is a large molecule built up by the repetition of small, simple
chemical units (Billmeyer, 1971). In some cases the repetition is linear, as in
a chain composed of a succession of links or they may be branched or
interconnected to form three-dimensional networks. This repetitive structure
is called the repeat unit and polymers may be made from a single type of
repeat unit or a combination, of a limited number, of types of repeat units.
Such polymers are referred to as homo-polymers and co-polymers respectively.
Polymers in fibres will have at least 100 repeating units in the chain, although
most will have thousands (Adanur, 1995). If one regards atoms as the smallest
unit of construction for molecules, then the large, mainly linear, polymeric
macromolecules are the essential building blocks for the construction of
natural or man-made fibres (Adanur, 1995).
With the exception of carbon fibres, glass fibres, metallic fibres and ceramic
fibres, the majority of natural or man-made fibres in general commercial use
are organic structures with a carbon–carbon chain backbone (Denton and
Daniels, 2002). Polyolefin polymers are essentially high molar mass, saturated,
aliphatic hydrocarbons, some of which can be conveniently spun into fibres.
The terms ‘polyolefin fibres’ and ‘olefin fibres’ are the generic names approved
by the United States Federal Trade Commission to describe a manufactured
fibre in which the fibre forming substance is any long-chain synthetic polymer
composed of at least 85% by mass of ethene (ethylene), propene (propylene),
or other olefin units of general formula (CH2==CH—X), where X represents
an alkyl chain (Denton and Daniels, 2002).

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Types of polyolefin fibres

5

The term polyolefin also includes the International Standards Organisation
(ISO) generic names of polypropylene (PP) and polyethylene (PE) as defined
in ISO 2706, although the correct chemical names should be poly(propene)
and poly(ethene), respectively, propene and ethene being the modern chemical
names for propylene and ethylene (Denton and Daniels, 2002). The structure
of the repeat unit is usually equivalent to that of the monomer, or the starting
material from which the polymer is formed. Thus the repeat unit of
polypropylene is [—CH2CH(—CH3)—] and the monomer is propene (or
propylene), CH2==CH—CH3. The monomers and equivalent repeat units for
selected polyolefins are shown in Table 1.1.

1.3

Chemistry of alkene (olefin) monomers

To understand ‘what polyolefins are’ or indeed to appreciate the whole gamut
of interactive science and technology related to polyolefin textiles, one must
start with the basic chemistry and structure of the alkene monomers from
which these commercially important polymers are made. Alkenes are a series
of unsaturated hydrocarbons with a general chemical formula of CnH2n. The
first member of the series is ethene (ethylene), C2H4, followed by propene
(propylene), C3H6 and butene C4H8, and so on. The distinguishing structural
feature of alkenes is the presence of at least one carbon–carbon double bond.
Quantum mechanics has enabled the structure of the carbon–carbon double
bond to be elucidated, as a combination of two different bond types, namely
a strong σ (sigma) bond (or single bond) and the other, a weak π (pi) bond.
Analysis of the quantum mechanical arrangement around the carbon–carbon

double bond in ethene indicates that ethene is a flat symmetrical molecule
with all six atoms on the same plane (Morrison and Boyd, 1983). The all
important π bond may be envisaged, in quantum mechanical terms, as an

Table 1.1 Structures of some polyolefins and their equivalent repeat units
Polymer

Alkene monomer

Polyolefin repeat unit

Poly(ethylene)
Poly(propylene)

Poly(1-butene)

CH2==CH2
CH2==CH (—CH3)
CH2==CH
L
CH2—CH—CH3
L
CH3
CH2==CH
L
CH2—CH3

[— CH2CH2 —]
[—CH2CH (—CH3) —]
[—CH2CH —]

L
CH2—CH—CH3
L
CH3
[—CH2 —CH—]
L
CH2—CH3

Poly(methyl1-butene)

CH2==CH
L
CH2—CH2
L
CH3

[—CH2—CH—]
L
CH2—CH2
L
CH3

Poly(4-methylpent1-ene)

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6

Polyolefin fibres

electron probability cloud, above and below the plane of the molecule and
lying between the two carbon atoms (see Fig. 1.1).
It is this special distribution of the electrons in the π (pi) bond that is
responsible for the reactivity of the carbon–carbon double bond with a wide
range of chemical reactants (Morrison and Boyd, 1983). Ethene has the
ability to react with itself to form dimers, trimers, tetramers, oligmers, etc. If
the reaction conditions are favourable, ethene has the potential to form long
saturated hydrocarbon macromolecules or polymers. Work on the
polymerisation of ethene began in the 1930s (Gibson, 1964). In those early
days, the researchers’ success was no mean feat and in retrospect was
responsible for the initiation of the commercial manufacture of hydrocarbon
polymers and the polyolefins industry as we know it today.
Whilst carbon–carbon single bonds are free to rotate through 360°, carbon–
carbon double bonds are locked firmly in place and are not free to rotate.
Thus if one substitutes one of the hydrogens on ethene to give an organic
molecule of the type CH2==CH—X, then this molecule will take on a definitive
three-dimensional structure. This has an effect on how such molecules react
or interact with other materials. For example, the substitution of one of the
hydrogens in the ethene molecule for a methyl group (—CH3) introduces us
to the second member of the alkene series, propene, more commonly referred
to as propylene, CH2==CH—CH3. The quantum mechanical arrangement
around the carbon–carbon double bond remains more or less the same as in
ethene, but the methyl group does have shape and size and imposes a definitive
geometric pendant to the molecule. The simple symmetry of ethene is lost
and the series of alpha substituted alkenes (CH2==CH—X) begins. Naturally
the size and shape of the pendant group determines the potential of these
alpha substituted alkenes to be converted into commercially useful polymers
(see Table 1.1).

1.4

Polymers and polymerisation reactions

In 1929, Wallace H. Carothers suggested that polymeric materials should be
classified as either addition or condensation polymers (Billmeyer, 1971).
H
H

C

C

H
H

Planar ethene molecule with C
H
H

C

C

C bond

H
H

Pi bonds in ethene: electron cloud above

and below the plane of the molecule

1.1 Chemical and bond structure of ethene.

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