Synthesis and Characterization of Polyurethanes With High Content of Biuret Groups

An \u27H-NMR and 13C NMR study of the reaction between urea and 4,4\u27-diphenylmethanedisocyanate is reported. Assignments for individual signals of biuret groups were determined and their concentration dependence on the reaction time was established. The rate constants for different biuret oligomers were calculated. From biuret oligomers and urethane oligomers block cooligomers and later block copolymers were formed