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Title: Analysis of cocondensation of melamine and urea through carbon 13 enriched formaldehyde with C-13 nuclear magnetic resonance spectroscopy
Author: Tomita, Bunichiro; Hse, Chung-Yun;
Source: Japan Wood Research Society 41(5):490-497
Publication Series: Miscellaneous Publication
Description: The urea-formaldehyde (UF) resins, melamine-formaldehyde (MF) resins, and melamine-ureaformaldehyde (MUF) cocondensed resins were synthesized using the labeling method with 13C enriched formaldehyde under neutral conditions and their 13C-NMR (nuclear magnetic resonance) spectra were analyzed. The remarkable down-field shifts by 1.2 to 2.7 ppm of the corresponding signals of UF and MUF resins were recognized by the addition of water to the DMSO-d4 solution of NMR samples. According to the results, the chemical shifts were corrected by measurements of DMSO-d4 solution free of water. The formation of cocondensed methylene linkages was induced mainly by the reaction of methylol groups of melamine and primary amino groups of urea residue, and that of cocondense dimethylene ether linkages was apt to take place in the case of a shortage of primary amino groups of urea residue. In the reaction of methylolurea and dimethylolmelamine, methylol groups of urea residue also were found to react with the primary amino group of methylolmelamine o form cocondensed methylene linkages.
Keywords: Melamine/urea, formaldehyde, cocondensation, C-13 NMR, C-13 enriched formaldehyde
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Tomita, Bunichiro; Hse, Chung-Yun 1995. Analysis of cocondensation of melamine and urea through carbon 13 enriched formaldehyde with C-13 nuclear magnetic resonance spectroscopy. Japan Wood Research Society 41(5):490-497
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