The chemistry and technology of polymers has developed rapidly during the last three decades; it concerns itself with materials consisting essentially of the elements C, H, N, and O, and being therefore conventionally classified as organic polymers. However, in many instances other elements such as B, Si, P, S, F, and CI are present in certain proportions and have a more or less important influence on the ultimate properties of the products. Together with the large family of metallic compounds and ceramic systems, organic polymers represent useful and increasingly important engineering materials in the construction of buildings, vehicles, engines, applicanes, textiles, packaging, printing and writing materials, plastics, rubber goods and household articles of all kinds.