The isocyanate reaction between an isocyanate group and a hydroxyl group has been known since 1849 when Ann Wurtz obtained the first patent in this field (German Patent 71326). The polymer, containing a repetitive moiety that results from the reaction between an isocyanate group and a hydroxyl group, is a polyurethane. Its morphology depends on the structure and nature of the diol and the respective isocyanate.