Polyurethane Polymers: Blends and Interpenetrating Polymer Networks

Sabu Thomas, Janusz Datta, Jozef T. Haponiuk, Arunima Reghunadhan, Jozef Haponiuk

• Publisher: Elsevier
• Year: 2017
• Print ISBN: 9780128040393
• eBook ISBN: 9780128040850
• Topic: Technology & Engineering
• Subtopic: Materials Science
• Index: Technology & Engineering

Polyurethane Polymers: Blends and Interpenetrating Networks deals with almost all aspects of blends and IPNs formed by polyurethane, including the thermal, mechanical, morphological, and viscoelastic properties of each blend presented in the book. In addition, major applications related to these blends and IPNs are mentioned. - Provides an elaborate coverage of the chemistry of polyurethane, including its synthesis and properties - Includes available characterization techniques - Relates types of polyurethanes to their potential properties - Discusses blends options

Chapter 1

Polyurethanes

Structure, Properties, Synthesis, Characterization, and Applications

Arunima Reghunadhan and Sabu Thomas, Mahatma Gandhi University, Kottayam, Kerala, India

Abstract

The chapter gives an introduction to the polyurethane (PU) polymer, its synthesis and its structure. The chapter details the different methods of polyurethane synthesis, various starting materials and the necessary components required for PU synthesis. The chapter also deals with the phase separation process of polyurethane and the effect of phase separation on the morphology, thermal, and mechanical properties of PU. The application of spectral techniques such as FTIR and NMR in the structural determination of polyurethane are also covered.

Keywords

Polyurethane; structure; morphology; phase separation; spectra

Contents

1.1 Introduction 1

1.2 Types of Polyurethanes, their Properties and Applications 2

1.3 Synthesis and Chemistry of Polyurethanes 3

1.4 Structural Analysis of Polyurethanes 7

1.5 Phase Separation and Miscibility 8

1.6 Characterization of Polyurethanes 11

1.7 Conclusions 15

References 15

1.1 Introduction

Polyurethanes (PUs) are a versatile class of polymers in both synthesis and applications. The superior properties make them suitable for a wide range of applications. They have very good mechanical properties, chemical resistance, and resilience. The presence of reactive functionalities in the main chain of polyurethane increases its compatibility with most polymers and so is suitable for the formation of networked structures. Polyurethane differs from normal polymers in that there are no urethane monomers. The chemical linkage existing in the polymer is denoted as urethane (–NHCOO–) and is the most reactive moiety in the polyurethane. Dependent on the starting materials, the end product differs in its nature, properties, and applications. From its first synthesis in 1937 by the genius German chemist Prof. Otto Bayer through a normal polyaddition reaction, it has been the most demanded plastic all over the world. Otto Bayer is recognized as the father of polyurethane. The polyurethane synthesis chemistry is easy in its basics, but becomes complex in the laboratory setting. The variety in the starting material and the additives and catalysts makes the synthetic route complex.

Polyurethanes are synthesized by the addition of alcohols and isocyanates. Diols or polyols are the alcoholic part and the diisocyanates are reacted with them. As a good variety of both these components are available easily, a large variety of polyurethanes can be obtained. PU can be soft, as in the case of foams, or hard, as in the case of automotive parts. Polyurethane exists in may forms in our lives, from clothes to footwear, from your bed to the house’s roofing material, from cars through to the construction field [1]. They are in every part of our daily life.

1.2 Types of Polyurethanes, their Properties and Applications

Different types of polyurethanes are available according to their synthetic route and applications. Commonly available polyurethanes are PU foams. Polyurethane foams may be low density flexible foams or low density rigid foams [2]. Low density flexible foams are used for furniture, truck seating, and cushions. The properties required for the usage in such industries are the flexibility, resilience, high mechanical strength, and durability. Rigid foams have high mechanical strength, low heat conduction, low moisture absorption, and low density. They are used as core materials in the manufacturing of thermal insulations in refrigerators and building insulation panels.

Another type is PU elastomers. They have low cost, resistance to high loads, high compression strength, and they can be easily formulated and colored. Polyurethane elastomers are considered as substitutes for plastics and rubbers. They have high abrasion resistance, resistance to solvents and chemicals, high impact strength, and low moisture uptake. These superior mechanical properties make them suitable for the manufacturing of packaging materials, in the health product industry, and the printing industry. They are also used in wheels, rollers, pulleys, shock absorbers, and bushings. Low density elastomers are used in the footwear industry for making shoe soles.

The most important class of polyurethanes are thermoplastic polyurethane. This type of material varies in its starting material and properties. Thermoplastic polyurethanes can be synthesized according to the required properties. They are similar to plastics and they have good elasticity and transparency. Thermoplastic polyurethanes (TPUs) are segmented polyurethanes with alternating hard and soft blocks. The length of the soft and hard blocks can be controlled during the synthesis. They are widely used in the medical equipment, castor wheels, power tools, sports, and the footwear industry. TPUs have high abrasion strength, high chemical and solvent resistance, and resistance to oil and grease.

1.3 Synthesis and Chemistry of Polyurethanes

Polyurethanes are reactive polymers similar to epoxies and polyesters. Polyurethanes are obtained from the reaction between diols and diisocyanates. Diols are systems with two –OH groups and an isocyanate contains –NCO group as the end point. PUs can be synthesized in a single step (the one shot method) by direct mixing of the components or in the prepolymer method. The prepolymer method involves the addition of diol and isocyanate to form the polyurethane prepolymer with –NCO as end groups. This prepolymer is then extended with chain extenders to form polyurethanes. The most commonly used isocyanates for the synthesis of polyurethane are diphenylmethane diisocyanate (MDI) or toluene diisocyanate (TDI), hexamethylene diisocyanate (HDI) or isophorone diisocyantate (IPDI). Aromatic isocyanates are more reactive than the aliphatic varieties. Polyols used for the synthesis of PUs can be polyether polyols and polyester polyols. The polyether polyols are ethylene glycol, p...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• List of Contributors
• List of Figures
• List of Tables
• List of Schemes
• Chapter 1. Polyurethanes: Structure, Properties, Synthesis, Characterization, and Applications
• Chapter 2. Blends and Interpenetrating Polymer Networks Based on Polyurethane Polymers With Natural and Synthetic Rubbers
• Chapter 3. Blends and IPNs of Polyurethane Polymers with Thermosetting Polymers
• Chapter 4. Role of Nanofillers in Polyurethane Based Blends and Interpenetration Networks
• Chapter 5. Polyurethane Ionic Blends as the Electrically Conductive Coatings
• Chapter 6. Blends and IPNs of Polyurethane Polymers With Block Copolymers
• Chapter 7. Nonisocyanate Polyurethanes
• Chapter 8. Conducting Polyurethane Blends: Recent Advances and Perspectives
• Chapter 9. Electrospun Polyurethane Nanofibrous Mats for Wound Dressing Applications
• Chapter 10. Poly(urethane-methacrylate) Copolymers Prepared by the Atom Transfer Radical Polymerization Methods as a New Material for Hydrophobic Coatings
• Chapter 11. Ageing Behavior of Polyurethane Based Blends and Interpenetrating Polymer Networks
• Chapter 12. Poly(urethane-siloxane) Copolymers as New Coating Materials
• Chapter 13. Polyurethane Blends for Powder Clear Coatings
• Chapter 14. Recycling of Polyurethanes
• Chapter 15. Application of Blends and Polyurethane Interpenetrating Polymer Networks
• Chapter 16. Mechanical and Dynamic Mechanical Properties of Polyurethane Blends and Interpenetrating Polymer Networks
• Index