Behaviour of polymers

Mustafa Akay

Mustafa Akay

Introduction to Polymer Science and Technology

Introduction to Polymer Science and Technology © 2012 Mustafa Akay & Ventus Publishing ApS ISBN 978-87-403-0087-1

Introduction to Polymer Science and Technology Contents

Contents

Preface 8

Acknowledgements 9

Introduction 10

1.1 History of the development of polymers 10

1.2 Why a clear understanding of material is important? 12

1.3 What can be achieved by appropriate selection of polymer-based materials? 17

1.4 What makes polymers versatile? 20

Polymerisation 31

2.1 Polymerisation mechanisms 31

2.2 Polymerisation processes 36

2.3 Polymerisation reactors 39

2.4 Catalysts 42

2.5 Molecular weight and molecular weight distributions 47

2.6 Self-assessment questions 50

Introduction to Polymer Science and Technology

Contents

Polymer processing

3.1 Concept of rheology

3.2 Processing and forming thermoplastics

3.3 Processing and forming thermosetting polymers

3.4 Self-assessment questions

Microstructure

4.1 Stereoregularity

4.2 Morphology in semi-crystalline thermoplastics

4.3 Degree of crystallinity

4.4 Crosslinking

4.5 Copolymer arrangements

4.6 Domain structures

4.7 Degree of molecular orientation

4.8 Self-assessment questions

Behaviour of polymers

5.1 Degradation of Polymers

5.2 Viscoelasticity

5.3 Relaxation transitions

5.4 Self-assessment questions

112 113 116 124 126 127 128 130

133 134 150 158

Introduction to Polymer Science and Technology Contents

163 166 179 184 186 187 189 196 199 202 206

210 218 221 225 248 257

Introduction to Polymer Science and Technology

To my parents (Rahmetullahi Aleyhima), to my wife, and to Mevlude, Latifa and Melek, the apples of my eye

Introduction to Polymer Science and Technology Preface

Preface

Learning involves acquiring knowledge, which is encouraged in all traditions. For example, the Quran urges people to seek knowledge and to use it for the well being of society:

"My Lord, increase me in knowledge", Al-Quran 20:114.

Knowledge should be applied in a safe, responsible and ethical manner not only to benefit us personally but also to improve the lot of the people we live with. It is also a duty to ensure that our surrounding habitat is not endangered. This sometimes requires knowledge of the local culture to help achieve a desirable outcome. Martin Palmer s presentation on BBC Thought for the Day programme, 17/06/2006, on the subject of the protection of the oceans included:

"To many around the world the environmental movement and its proffered solutions - usually economic - are alien ways of thinking and seeing the world, and can be interpreted as telling people what is best for them whether they like it or not. Let me tell you a story. Dynamite-fishing off the East African coast is a major problem. Environmental organisations have been addressing it for years, from working with Governments, to sending armed boats to threaten those illegally fishing. None of this worked because it had no relationship to the actual lives or values of the local fishermen all of whom are Muslims. What has worked off one island, Misali, is the Qur'an. In the Qur'an, waste of natural resources is denounced as a sin. Once local imams had discovered this, they set about preaching that dynamite fishing was anti-Islamic, non-sustainable and sinful. This ended the dynamite fishing of the Misali fishermen because it made sense to them spiritually."

The subject of this book is covered in seven chapters. The chapters are arranged in an attempt to reflect the three pillars of materials science and technology: in materials, there is a strong link between processing, microstructure and properties. Changing one affects the others and this has enabled scientists/engineers to tailor materials to suit purposes. Nature provides many examples of how materials comply with the processing-microstructure-properties relationship, e.g., one of the wonders of the world, the Giants Causeway consists of regular columns of polygonal slabs of volcanic basalt deposition juxtaposed the same material in rubble form with no recognisable shape. Based on the prevailing conditions, particularly that of temperature and the rate of cooling, the lava has solidified in regular as well as irregular forms. The processing-properties link is also highlighted by Leo Baekeland, the inventor of the first commercial plastic:

"I was trying to make something really hard, but then I thought I should make something really soft instead, that could be molded into different shapes. That was how I came up with the first plastic. I called it Bakelite."

Chapter 1 in this bookis introductory and includes a history of the development of polymers; the importance of the knowledge of materials for engineers and technologists; what makes polymeric materials attractive over conventional materials and a description of the versatile nature of polymers. The subsequent two chapters deal with the polymerisation processes and the processes employed in the conversion of polymeric raw materials into products. Chapter 4 covers the microstructural features in polymers, including lamellae, spherulites, crosslinking, and the measurements of degrees of crystallinity and molecular orientation. The viscoelastic nature of polymers, the time/temperature sensitivity of viscoelasticity and how this manifests itself in the form of creep, stress relaxation and mechanical damping are covered in Chapter 5. Glass transition and its dependence on molecular features are also covered in Chapter 5. The last two chapters cover various aspects of mechanical and thermal properties of polymers. Writing this book has been educational, and I thank BookBoon for giving me the opportunity.

Mustafa Akay, N. Ireland, February 2012

Introduction to Polymer Science and Technology Acknowledgements

Acknowledgements

The book emerges from my work at the Ulster Polytechnic/University of Ulster, where I met and worked with various characters and personalities and I would like to mention Lesley Hawe, the late Archie Holmes and Myrtle Young who epitomise for me the constant kindness, help and support I received from the academic, technical and secretarial staff over the years.

The book incorporates material taken from various sources, including my lecture notes, research outcomes of my postgraduate students, some of them have become friends for life, and some excellent text books, research papers/news, industry/company/organisation literature and web material that we are so fortunate to have access to. The sources of the materials used are gratefully acknowledged and are listed as references, however, over the years material permeates into teaching notes that is not always possible to trace the references for. I apologise, therefore, for any such material that has no accompanying reference and I express my thanks and gratitude to the people concerned.

A special thank you goes to my wife for the offers of regular walks to blow away the cobwebs and visits to "Mugwumps" for coffee.

Introduction to Polymer Science and Technology Introductions

1 Introduction

1.1 History of the development of polymers

"Genius is one percent inspiration and ninety-nine percent perspiration." Thomas A. Edison,1847-1931.

Edison, one of the most prolific inventors in history, has appreciated the work of others, believed in team working, and has stated, "I start where the last man left off." Over time, the work of the pioneers of polymer science, some listed below, has been gratefully acknowledged by others and developed upon.

1839 Eduard Simon discovered polystyrene.

1843 Hancock in England and Goodyear in USA developed the vulcanisation of rubberby mixing it with sulphur. Charles Goodyear epitomizes the 99% perspiration attitude: toiled all his life in spite of many set-backs and disapp ointments.

1854 Samuel Peck produced "union cases" for photographs by mixing shellac (produced from the secretions of the lac beetle which live on trees native to India and South-East Asia) sawdust, other chemicals and dye, and heated and pressed the mixture into a mould to form the parts of a Union Case. The term "union" refers to the material composition, i.e., synonymous with the terms mixture or blend.

1862 Alexander Parkes exhibited Parkesine, made from cellulose nitrate,at an International Exhibition in London.

1868 The Hyatt brothers in America produced celluloid from cellulose nitrate mixed with camphor. This was unstable
and subsequently led to the development of cellulose acetate. They developed many of the first plastics mass
production techniquessuch as blow moulding, compression moulding and extrusion.

1869 Daniel Spill took over the rights to manufacture Parkesine in England and established the Xylonite Company
producing Xylonite and Ivoride.

1872 Eugen Baumann, one of the first to invent polyvinyl chloride(PVC).

1897 Spitteler in Germany patented casein, marketed as Galalith, made from protein from milk mixed with formaldehyde.

1907 Leo Baekeland produced phenol-formaldehyde,the first truly synthetic plastic, Bakelite. Cast with pigments to resemble onyx, jade, marble and amber it has come to be known as phenolic resin.

1910 The Dreyfus brothers perfected cellulose acetate lacquersand plastic film.

1912 Fritz Klatte discovered polyvinyl acetateand patented the manufacturingprocess for PVC.

Introduction to Polymer Science and Technology Introduction

1924 Rossiter produced urea thiourea formaldehyde, marketed as Linga Longa or as Bandalasta ware by British Cyanides.

1928 Otto Rohm in Germany stuck two sheets of glass together using an acrylic ester and accidentally discovered safety glass, and production of some articles began in 1933.

1933 ICI discovered polyethylene.

1933 Melamine formaldehyderesins were developed through the 1930s and 1940s in companies such as American Cyanamid, Ciba and Henkel.

1935 Wallace Carothers,working for DuPont, invented poly(hexamethylene-adipamide), Du Pont named this product
nylon.Carothers did not see the widespread application of his work in consumer goods such as toothbrushes,
fishing lines, and lingerie, or in special uses such as surgical thread, parachutes, or pipes, nor the powerful effect
it had in launching a whole era of synthetics. Sadly, he died in early 1937 at the young age of 41.

1936 Polymethyl methacrylate sheet,Perspex, was cast by ICI, and shortly after it was employed in aircraft glazing.

1936 The Wulff brothers in Germany produced commercially viable polystyrene.

1937 Otto Bayer patented polyurethane.

1938 Roy Plunkett working for DuPont accidentally discovered poly(tetra fluroethylene),PTFE, trademarked Teflon.
1941 Commercial development of polyestersfor moulding began in the USA.

1941 Polyethylene terephthalate(PET), a saturated polyester patented by John Rex Whinfield and James Tennant Dickson.

1948 Acrylonitrile butadiene styrene(ABS).

1951 Paul Hogan and Robert Banks of Phillips Petroleum discovered high-density polyethyleneand crystalline polypropylene.

1953 Polyethylene polymerisation was achieved at low pressures using Ziegler catalysts.

1954 Giulio Natta succeeded in "stereospecific" polymerisation of propylene with Ziegler-type catalysts. Karl Ziegler
and Giulio Natta received the Nobel Prize in Chemistry for their work in 1963.

1958 Polycarbonatewas put into mass manufacture.

1964 Stephanie Louise Kwolek of DuPont developed Kevlar fibre from polyaramide(an aromatic polyamide).

1987 BASF in Germany produced a polyacetylenethat has twice the electrical conductivity of copper.

Introduction to Polymer Science and Technology Introduction

ICI published the book entitled "Landmarks of the Plastics Industry: 1862-1962" to mark the centenary of Alexander Parkes' invention of the worlds first man-made plastic, and to pay tribute to those who have helped to establish the modern plastics industry and to those who are working towards its improvement and expansion.

Products, machinery and constructions all require the employment of materials and energy. What materials are used depends on availability, cost and, of course, suitability for purpose. As metal replaced wood in many consumer products, plastics were developed as an even cheaper alternative. The cost of casting metal increased sharply after World War II, while plastic could be formed relatively cheaply. For this reason plastics gradually replaced many things that were originally made in metal. However the choice of material requires sound judgement. Accordingly the subject of materials is taught on traditional engineering courses mechanical, civil and electrical as well as others such as sports technology and bio-medical engineering.

The importance of materials and the need for a sound awareness and understanding of materials for engineering practitioners is further explored below. The website 'whystudymaterials.ac.uk' also includes topics of interest in this regard.

1.2 Why a clear understanding of material is important?

In days gone by, all that the designer/engineer had to work with was cast iron, a limited range of steel, some non-ferrous metals and wood. Today, we are faced with a bewildering choice of materials and the problem of comparing materials of different types and from different suppliers. As scientists and engineers a clear understanding of these materials is vital in order to:

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