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...