Integral, or structural, foams are one of the most remarkable materials that have been developed over the last fifteen years. As with all rapidly growing fields, the terminology seems to have grown even faster. Thus there are two names for the material structure itself. In the United States and in Japan the term for these plastics is Structural Foams, whereas in Europe and the USSR the term used is usually Integral Foams. We have adhered to the European term in the text and hope our colleagues will bear with us. Integral foams have a specific structure: a cellular core that gradually turns into a solid skin. The skin gives the part its form and stiffness, while the cellular core contributes to the very high strength-to-weight values of the material. These are higher than those of some unfoamed plastics and metals. The sandwich-like structure with its unique mechanical properties was prompted by nature. Wood and bone are strong and light-weight natural materials having a cellular structure. Since the sandwich-like structure of the integral foams resembles that of natural wood, the foams are often referred to as artifical wood or plastic wood, thereby emphasizing not only the formal structural similarity of these materials, but also one of the main functional applications of integral foams - replacement of wooden articles in various fields of engineering and construction.

During the oil embargo, in the winter 1973174, parts of Western Europe present ed an almost war-like aspect on Saturdays and Sundays: no traffic on the high ways, no crowds at ski resorts and other weekend entertainment places, no gaso line at the pumps. Living and teaching then in that part of the world, and discussing the situa tion with our students, we came to the conclusion that it would be timely to col lect the fine chemistry already known at the time in the field of conversion of coal to gasoline and other chemicals, and by this way help to draw the attention to this important alternative to crude oil. The idea of this book was born. The energy shock of the early seventies has been healthy and of great conse quences in chemistry. Large amounts of research money have been put to work since, and our knowledge of the possibilities and limitations of coal-based chemistry has increased enormously. During several years it appeared inap propriate to write a monograph about a topic which was in the midst of such an impetuous development. Nevertheless, we collected, and critically selected, the upcoming work as it appeared in the literature, and also tried to provide some modest input ourselves. Now, ten years later, the situation seems to be settled to a certain degree."