Synthetic Methods in Step-Growth Polymers - Hardcover

Hardcover

ISBN 10: 047138769X ISBN 13: 9780471387695

Verlag: Wiley-Interscience, 2003

Inhaltsangabe

Synthetic Methods in Step-Growth Polymers provides a concise source of information on synthetic techniques, purification, and characterization methods for step-growth polymers and also addresses future synthetic trends.

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Über die Autorin bzw. den Autor

MARTIN E. ROGERS, PhD, is Senior Research Scientist at Luna Innovations in Blacksburg, Virginia.

TIMOTHY E. LONG, PhD, is Professor of Chemistry at Virginia Polytechnic Institute and State University in Blacksburg, Virginia.

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An applications-oriented resource on step-growth polymerization

Step-growth polymers-polymer chains of any length that combine to form a longer polymer chain-comprise a large portion of the commodity plastics industry today, including polyesters, polyamides, and polyurethanes. Synthetic Methods in Step-Growth Polymers provides a concise source of information on synthetic techniques, purification, and characterization methods for step-growth polymers and also addresses future synthetic trends.

This applications-oriented handbook is a one-stop, at-your-fingertips source of information for researchers, technologists, and industrial managers. Encompassing a single reference of the classical and state-of-the-art synthetic techniques for preparing polymers via step-growth polymerization, Martin Rogers and Timothy Long's text provides a historical background of step-growth polymerization, basic information regarding major classes of step-growth polymers, and experimental techniques such as purification, synthesis, and characterization. Chapters include:
* Polyurethanes and Polyureas
* Polyimides and Other High-Temperature Polymers
* Non-Traditional Step-Growth Polymerization-ADMET
* Non-Traditional Step-Growth Polymerization-Transition Metal Coupling
* Depolymerization and Recycling

All chapters are contributed by leading experts in their respective fields. Chemists, chemical engineers, and materials scientists, as well as industrial, academic, and government libraries, will find Synthetic Methods in Step-Growth Polymers to be an unparalleled resource for this category of polymerization.

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Synthetic Methods in Step-Growth Polymers

John Wiley & Sons

Copyright © 2003 John Wiley & Sons, Inc.
All right reserved.
ISBN: 978-0-471-38769-5

Chapter One

Introduction to Synthetic Methods in Step-Growth Polymers

Martin E. Rogers Luna Innovations, Blacksburg, Virginia 24060

Timothy E. Long Department of Chemistry, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061

S. Richard Turner Eastman Chemical Company, Kingsport, Tennessee 37662

1.1 INTRODUCTION

1.1.1 Historical Perspective

Some of the earliest useful polymeric materials, the Bakelite resins formed from the condensation of phenol and formaldehyde, are examples of step-growth processes. However, it was not until the pioneering work of Carothers and his group at DuPont that the fundamental principles of condensation (step-growth) processes were elucidated and specific step-growth structures were intentionally synthesized. Although it is generally thought that Carothers' work was limited to aliphatic polyesters, which did not possess high melting points and other properties for commercial application, this original paper does describe amorphous polyesters using the aromatic diacid, phthalic acid, and ethylene glycol as the diol. As fundamental as this pioneering research by Carothers was, the major thrust of the work was to obtain practical commercial materials for DuPont. Thus, Carothers and DuPont turned to polyamides with high melting points and robust mechanical properties. The first polymer commercialized by DuPont, initiating the "polymer age," was based on the step-growth polymer of adipic acid and hexamethylene diamine-nylon 6,6. It was not until the later work of Whinfield and Dickson in which terephthalic acid was used as the diacid moiety and the benefits of using a para-substituted aromatic diacid were discovered that polyesters became commercially viable.

In these early days of polymer science, the correlation of structure and property in the newly synthesized structures was a daunting challenge. As Carothers said, "problem of the more precise expression of the relationships between the structures and properties of high polymers is complicated by the fact that some of the properties of this class of substances which are of the greatest practical importance and which distinguish them most sharply from simple compounds can not be accurately measured and indeed are not precisely defined. Examples of such properties are toughness and elasticity" (ref. 6, p. 317).

Today, step-growth polymers are a multi-billion-dollar industry. The basic fundamentals of our current understanding of step-growth polymers from monomer functionality to molecular weight distribution to the origins of structure-property relationship all had their beginnings in the pioneering work of Carothers and others at DuPont. A collection of these original papers offers an interesting and informative insight into the development of polymer science and the industry that it spawned.

1.1.2 Applications

In general, step-growth polymers such as polyesters and polyamides possess more robust mechanical properties, including toughness, stiffness, and higher temperature resistance, than polymers from addition polymerization processes such as polyolefins and other vinyl-derived polymers. Even though many commercial step-growth polymerization processes are done on enormous scale using melt-phase processes, most step-growth-based polymers are more expensive than various vinyl-based structures. This is, at least in part, due to the cost of the monomers used in step-growth polymerizations, which require several steps from the bulk commodity petrochemical intermediates to the polymerizable monomer, for example, terephthalic acid from the xylene stream, which requires oxidation and difficult purification technology. These cost and performance factors are key to the commercial applications of the polymers.

Most of the original application successes for step-growth polymers were as substitutes for natural fibers. Nylon-6,6 became an initial enormous success for DuPont as a new fiber. Poly(ethylene terephthalate) (PET) also found its initial success as a textile fiber. An examination of the polymer literature in the 1950s and 1960s shows a tremendous amount of work done on the properties and structures for new fibers. Eventually, as this market began to mature, the research and development community recognized other commercially important properties for step-growth polymers. For example, new life for PET resulted from the recognition of the stretch-blow molding and barrier properties of this resin. This led to the huge container plastics business for PET, which, although maturing, is still fast growing today.

The remainder of this introductory chapter covers a few general but important parameters of step-growth polymerization. References are provided throughout the chapter if further information is desired. Further details of specific polymers made by step-growth polymerization are provided in subsequent chapters within this book.

1.2 STRUCTURE-PROPERTY RELATIONSHIPS IN STEP-GROWTH POLYMERS

1.2.1 Molecular Weight

Polymers produced by step-growth polymerization are composed of macromolecules with varying molecular weights. Molecular weights are most often reported as number averages, [bar.Mn], and weight averages, [bar.Mw]. Rudin, in The Elements of Polymer Science and Engineering, provides numerical descriptions of molecular weight averages and the derivation of the molecular weight averages. Other references also define molecular weight in polymers as well as methods for measuring molecular weights. Measurement techniques important to step-growth polymers include endgroup analysis, size exclusion chromatography, light scattering, and solution viscometry.

The physical properties of polymers are primarily determined by the molecular weight and chemical composition. Achieving high molecular weight during polymerization is critical if the polymer is to have sufficient thermal and mechanical properties to be useful. However, molecular weight also influences the polymer melt viscosity and solubility. Ease of polymer processing is dependent on the viscosity of the polymer and polymer solubility. High polymer melt viscosity and poor solubility tend to increase the difficulty and expense of polymer processing.

The relationship between viscosity and molecular weight is well documented. Below a critical molecular weight, the melt viscosity increases in proportion to an increase in molecular weight. At this point, the viscosity is relatively low allowing the material to be easily processed. When the molecular weight goes above a critical value, the melt viscosity increases exponentially with increasing molecular weight. At higher molecular weights, the material becomes so viscous that melt processing becomes more difficult and expensive.

Several references discuss the relation between molecular weight and physical properties such as the glass transition temperature and tensile strength. The nature of thermal transitions, such as the glass transition temperature and crystallization temperature, and mechanical properties are discussed in many polymer texts. Below a critical molecular weight, properties such as tensile strength and the glass transition temperature are low but increase rapidly with increasing molecular weight. As the molecular weight rises beyond the critical molecular weight, changes in mechanical properties are not as significant. When developing polymerization methods, knowledge of the application is...

Details zur Ausgabe

• Verlag: Wiley-Interscience
• Erscheinungsdatum: 2003
• Sprache: Englisch
• ISBN 10: 047138769X
• ISBN 13: 9780471387695
• Einband: Gebundene Ausgabe
• Auflage: 1
• Anzahl der Seiten: 624
• Herausgeber: Rogers Martin E., Long Timothy E.
• Kontakt zum Hersteller: Wiley-VCH GmbH; product_safety@wiley.com; ; Boschstrasse 12; Weinheim; 69469; Deutschland