13C‐NMR analysis of formaldehyde resins

Abstract 13C‐NMR spectroscopy has been applied to the analysis of formaldehyde containing resins. Samples have been prepared from phenols, urea and melamine with formaldehyde. The chemical shifts of the carbon atoms in the resins were measured relative to TMS. All the samples could be dissolved in DMSO‐d6 which facilitated the comparison of signals in different resins. The spectra were interpreted with the aid of spectra of reference compounds and simple calculations based on additivity increments. Each type of resin gives a specific 13C‐NMR spectrum in which lines can be assigned that give information on the structure of the resin in relation to the type of condensation or catalyst used. Moreover, the different ways in which formaldehyde is incorporated in the resins as methylene carbon can be unambiguously determined from the region between 20 and 100 ppm. This work shows that 13C‐NMR spectroscopy is a powerful tool for the analysis of formaldehyde containing resins.