ANALYSES OF COCONDENSATION OF MELAMINE AND UREA THROUGH FORMALDEHYDE WITH CARBON-13 NUCLEAR-MAGNETIC-RESONANCE SPECTROSCOPY

The C-13-NMR (carbon 13 nuclear magnetic resonance) spectra of urea-fo rmaldehyde (UF) resins, melamine-formaldehyde (MF) resins, and melamin e-urea-formaldehyde (MUF) cocondensed resins synthesized under various conditions were taken with a frequency of 75 MHz. The main purpose wa s to investigate whether or not the occurrences of cocondensation betw een melamine and urea through the formations of methylene or dimethyle ne ether linkages could be identified. The signals due to carbons of m ethylene linkages of UF resins were distinguishable from those of MF r esins. The signals due to carbons of cocondensed methylene linkages (- NH-CR(2)-NH-), in which both nitrogen atoms are secondary, were sugges ted to be identifiable separately from those due to UF and MF resins. The corresponding carbons of dimethylene ether linkages of UF and MF r esins could be identified clearly by the difference of their chemical shifts of 0.9 ppm. The carbon signals due to cocondensed dimethylene e ther linkages were found to appear at the chemical shifts between thos e due to UF and MF resins.