Determination of phenylurethane and isocyanate groups in isocyanates

Reactions of phenylurethane and isocyanate groups of arylisocyanates with s econdary amines are studied by IR spectrometry and potentiometric titration . It is found that the rate of the reaction between isocyanate groups and d iethylamine is nearly independent of the solvent nature. When protophilic s olvents are used, solvent molecules and isocyanate groups form associates, which interfere with the determination. Optimal conditions are determined f or the determination of phenylurethane and isocyanate groups. Procedures ar e developed for determining mass fractions of isocyanate and phenylurethane groups when they are present simultaneously.