Determination of epoxy and isocyanate groups in the presence of each other

Analytical reactions for the determination of epoxy and isocyanate groups in the presence of each other in epoxy-isocyanate compositions were studied. For the determination of epoxy groups in the presence of isocyanate groups, a test with HBr in glacial acetic acid was proposed; acetic acid reacts with isocyanate groups and, hence, masks them. Isocyanate groups in the presence of epoxy groups were determined by potentiometric titration with a solution of piperidine in ethyl methyl ketone. The addition of toluene to the test solution decreases the fraction of the enol form of ethyl methyl ketone, which interferes with the determination.