Investigations of the chemical structure of sulfonated amino‐formaldehyde resins. V. 13C‐NMR analysis of sulfonated urea–melamine–formaldehyde resins

Abstract 13C‐NMR spectroscopy was used to characterize the chemical structure of sulfonated urea–melamine–formaldehyde resins, prepared by a three‐step procedure (addition, sulfonation, condensation). Each of the three reaction steps was investigated separately and the average number of functional groups, obtained after each step, was determined quantitatively. The effect of the reactant ratios on the chemical structure was studied.