NMR structural elucidation of amino resins

Urea formaldehyde, melamine formaldehyde, and melamine urea formaldehyde (MUF) are important industrial amino resins that find application in numerous diverse areas, most notably in the bonding of wood products. To understand the physical properties of these amino resins and, hence, optimize their performance, a knowledge of their chemical structure is necessary. This article reports the use of NMR spectroscopy to acquire this information in the solid and liquid states. C-13-NMR experiments, supported and augmented by H-1-NMR and N-15-NMR results, showed that the two stages of resin synthesis, methylolation followed by condensation, occurred in each type of resin. However, in the various NWF samples analyzed, the second step appeared to be predominantly the self-condensation of melamine and urea rather than the cocondensation of melamine and urea. (C) 2004 Wiley Periodicals, Inc.