Boron-containing fire retardant rigid polyurethane–polyisocyanurate foams: Part II – preparation and evaluation

The method of preparation of boron compounds with the use of di(hydroxymethyl)urea derivatives and boric acid has been described. On the basis of our studies, it was found that application of the borates obtained, as a polyol component and simultaneously as a flame retardant in recipe for preparation of polyurethane–polyisocyanurate foams, had a positive effect on properties of foams. The resulting rigid foams were characterized by a lower brittleness, higher compressive strength and content of closed cells and significantly lower flammability in comparison with the standard foam. Flammability was determined by the methods of oxygen index, Butler’s test, infrared camera and cone calorimeter. The results of our studies showed that new polyols obtained on the basis of N,N′-di(methyleneoxy-4-hydroxybutyl)urea, N,N′-di(methyleneoxy-3-hydroxybutyl)urea, N,N′-di((methyleneoxy-2-hydroxymethylpropyl)urea and boric acid can be successfully applied for production of rigid polyurethane–polyisocyanurate foams. Application of the new compounds in recipe for preparation of foams improved their physico-mechanical properties.