Preface

Polyurethanes, invented back in the 1930s by Professor Dr. Otto Bayer (1902–1982), are one of the most versatile plastic materials. There are various types of polyurethanes, which look and feel very different from each other. The nature of the chemistry allows them to be adapted to solve challenging problems, to be molded into unusual shapes, and to enhance industrial and consumer products by adding comfort, warmth, and convenience to our lives. They are used in a variety of products, from coatings and adhesives to shoe soles, mat‐ tresses, and foam insulation. Yet, the basic chemistry of each type is essentially the same.

Polyurethanes are formed by reacting a polyol (an alcohol with more than two reactive hy‐ droxyl groups per molecule) with a diisocyanate or a polymeric isocyanate in the presence of suitable catalysts and additives. Because a variety of diisocyanates and a wide range of polyols can be used to produce polyurethane, a broad spectrum of materials can be pro‐ duced to meet the needs of specific applications.

During World War II, a widespread use of polyurethanes was first seen, when they were used as a replacement for rubber, which at the time was expensive and hard to obtain. Dur‐ ing the war, other applications were developed, largely involving coatings of different kinds, from airplane finishes to resistant clothing.

Subsequent decades saw many further developments, and today we are surrounded by pol‐ yurethane applications in every aspect of our everyday lives. While polyurethane is a prod‐ uct that most people are not overly familiar with, as it is generally "hidden" behind covers or surfaces made of other materials, it would be hard to imagine life without polyurethanes.

In the present book, we attempt to collect different topics and studies related to polyur‐ ethanes and their applications. In the first chapter, a discussion is done to illustrate a polyur‐ ethane-epoxy interpenetrating polymer network. Electrospun polyurethane nanofibers are illustrated in the second chapter. The third chapter is about polyurethane: a shape memory polymer (SMP). Also, measurement and numerical modeling of mechanical properties of polyurethane foams are discussed in the fourth chapter. Polyol containing boron atoms as a compound that reduces flammability of rigid polyurethane-polyisocyanurate foams; erosive and abrasive wear resistance of polyurethane liners; bio-based polyurethanes from carbohy‐ drate monomers; and dynamic mechanical behavior of polymer materials are discussed in the fifth, sixth, seventh, and eighth chapters, respectively.

> **Dr. Faris Yilmaz** FNSS Savunma Sistemleri A.Ş. Ankara, Turkey

**Provisional chapter**
