Abstract
The relationships of chemical structure and properties of rigid urethane foams have been discussed. General effects of chemical groups in urethane polymers have been related to physical properties. The specific effects of the various foam components such as variations of isocyanates, polyols, blowing agents, cata lysts, surfactants and the effect of isocyanate to hydroxyl ratio on rigid foam properties have been described. A number of ap proaches in imparting flame resistance to rigid urethane foams and some correlations between chemical structure and the flame re sistance of these foams have been presented.