Relative activities of a number of catalysts for isocyanate trimerization have been meas ured in order to select several having activi ties suitable for the preparation of rigid iso cyanurate foams. The effects of ring substitu ents on the rates of trimerization of phenyl isocyanate have been studied and attributed to a combination of steric and electronic fac tors. A series of rigid isocyanurate foams have been prepared by trimerization and simultaneous blowing of NCO terminated prepolymers. These foams retain dimensional stability and considerable strength up to 450°F., but degrade at about 480°F. Reac tions contributing to the degradation of these foams have been characterized by differ ential thermal analysis.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.