Heat Resistant Rigid Foams by Trimerization of Isocyanate Terminated Prepolymers

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Abstract
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.