Polyurethanes. Mark F. Sonnenschein

introduction of large chemical concerns that represent and depend on national subsidies, such as those appearing in China and Saudi Arabia. As a statement of a societal commitment apart from market forces, they are capable of distorting market supply and pricing. Whether by consolidation or spinning out of assets, the ability of the surviving companies to efficiently and effectively allocate and spend capital in the prevailing economic environment could be a continuing element in the polyurethanes industry story.

      This edition adds two new special chapters at the end: Chapter 13 on polyurethane hybrid polymers and Chapter 14 on polyurethane recycle. As the reader will see, both topics cover nascent technologies in terms of the scientific progress and industrial intent to commercialize in these technology fields. Polymer hybrids are often conceived in the belief that if two different polymers are good, then their combination (or hybridization) will be even better. While this has not historically been found true for a number of reasons, there are a number of instances for polyurethanes where polymer backbone hybridizations are beneficial, making this technology area potentially ripe for growth in the future.

      Polyurethane recycle – the subject of Chapter 14 – is a subset of the much larger topic of plastics recycle. However, unlike soda straws, water bottles, and disposable food packaging, polyurethanes are usually not found in articles that are commonly thrown away. There is no developed municipal collection and distribution system for acquiring polyurethanes, separating them from the objects they are a part of, and readying them for chemical cleanup and reversion back to useful building blocks. However, regulations, especially those emanating from the European Union, requiring end‐of‐life stewardship of things such as mattresses and automotive seats – containing significant volumes of polyurethanes – are forcing producers to develop technology and commercial partnerships. This industrial evolution will permit polyurethane recycle either through low‐value physical incorporation or by chemical transformation of the polyurethane polymer into useable feedstocks for making new materials. If governmental regulations create price inelastic demand for these materials, then the methods of their production and the value they bring will become a topic of increasing importance into the future.

      Mark F. Sonnenschein

      Midland, MI

ACKNOWLEDGMENTS

      I would like to express my deep gratitude to the people who have helped me through the years and provided fertile ground for growth. Particularly I would like to mention my colleagues whom I have worked with in the field of polyurethanes over the past 20 years. First, I would like to mention my constant collaborator Benjamin Wendt, who has worked with me closely in the lab for many years and excelled at making hard things work easily. Many people have provided guidance, encouragement, and excellent collaboration over the years. Especially I would like to mention Dr. Alan Schrock, Dr. Justin Virgili, Dr. Mark Cox, Dr. Jack Kruper, Dr. Chris Christenson, Dr. Valeriy Ginzburg, Dr. Jozef Bicerano, Mr. Will Koonce, Dr. Juan‐Carlos Medina, Prof. Tony Ryan, Dr. David Babb, Dr. Robbyn Prange, Dr. Nelson Rondan, Dr. Maria Pollard, Dr. Jai Venkatesan, Dr. David Bem, Dr. Florian Schattenmann, Dr. Andre Argenton, Dr. Jorge Jimenez, Dr. Kaoru Aou, Dr. Kshitish Patankar, Dr. Steve Guillaudeu, Dr. Cecile Boyer, Dr. Steve Montgomery, Dr. Brian Landes, Dr. Steve Webb, Dr. Phillipe Knaub, Dr. Hamdy Khalil, Dr. Tirtha Chatterjee, Dr. Lotus Huang, Dr. Cathy Tway, Dr. Shawn Feist, Prof. John Klier, Prof. Craig Hawker, and Dr. John Kramer.

      I would also like to recognize the great support I received from The Dow Chemical Company in writing this book by giving me the encouragement, time, resources, and freedom to realize this vision.

      I would be remiss to not acknowledge the contributions of my copy‐editor, Lindsey Williams. Her patient and meticulous contributions have made this a more readable and useful text.

      Lastly, I would like to acknowledge the people who gave me my scientific foundations and inspired in me a love of experiment and a respect for theory. Particularly I would like to mention Prof. Richard G. Weiss (Georgetown University), Dr. C. Michael Roland (The United States Naval Research Lab), and Prof. Gordon Johnson (Kenyon College) for putting up with me in my early years.

1 INTRODUCTION

In the early 1900s there were very few of the synthetic polymers we have grown accustomed to now. During succeeding years polymer science experienced explosive growth with the invention of polyvinyl chloride (PVC, 1913), polyethylene (1933), polyvinylidene chloride (Saran, 1933), polyamides (nylon, 1934), and polytetrafluoroethylene (Teflon, 1938). In addition, during the 1930s the polymer family known as polyurethanes was invented. Now, of course, polyurethanes, and all the polymers developed during this period, have become an integral part of modern life. As you read this you may not be aware of how many ways polyurethanes surround you. They are present in the shoes you stand in, the seat cushion you sit upon, the carpet backing and foam pad underlay you walk upon, in the fibers of your clothing, insulation of your walls and roof, in your refrigerator, dishwasher, water heater, automotive seating, automotive structural foam, automotive paints and coatings, furniture coatings, your bed mattress, the adhesive holding this book together – the list just goes on. This book’s purpose is to explain polyurethane science, technology, applications, trends, and markets in virtually all of its forms and relate those structures to the properties that make them so suited for so many uses. It is not an overstatement to say that if polyurethanes are not the most versatile class of materials, then they are certainly one of the most versatile polymer categories in existence.

      Discovery of polyurethane chemistry is attributed to the efforts of Otto Bayer and the research team he led at the now defunct I.G. Farben AG chemical company. The first patent associated with polyurethanes was filed in 1937 and numerous other patents, most notably the production of flexible foams resulting from isocyanate–water reactions, were filed thereafter. I.G. Farben was broken up following World War II for complicity in war crimes and the company’s top leaders were convicted of crimes against humanity (exploitation of slave labor and production of nerve gas). The largest surviving components of I.G. Farben – Bayer AG and BASF SE – remain very large and respected global industrial concerns. While BASF continues to engage with and maintain a significant presence within the polyurethane industry, Bayer spun off its polyurethane business and the rest of its industrial chemicals concerns into a new company called Covestro.

      After the initial discovery and expositions of basic chemistry, mostly based on short‐chain diols and polyester polyols, industrial polyurethanes saw immense growth following the development of polyether polyols by E.I. du Pont de Nemours and Company (now known as DuPont) and The Dow Chemical Company. While Dow Chemical remains one of the world’s largest manufacturers of polyurethane chemicals, DuPont has exited its polyurethanes businesses, which were primarily textile and coatings related. While polyesters remain prominent components of polyurethane chemistry, it was the superior processing, low‐temperature flexibility, and hydrolytic stability of polyether polyols that expanded polyurethane polymers into their current acceptance in every aspect of modern life.

As ubiquitous as polyurethanes are, it is perhaps surprising that they represent a relatively minor (but still significant) fraction of the overall global consumption of plastics by volume (Figure 1.1).

FIGURE 1.1 Percentage global consumption of plastics in 2018. Polyethylene encompasses all densities; styrenics includes all copolymers along with atactic polystyrene. These relative values are similar to those in the first edition using 2012 data. The consumption of many plastics grows at a rate relative to economic activity plus a small accelerator or decelerator for each given plastic’s role in the market. PET = polyethyene terephthate.

The