OPTIMIZING THE CONDITIONS OF QUANTITATIVE C-13-NMR SPECTROSCOPY ANALYSIS FOR PHENOL-FORMALDEHYDE RESOL RESINS

The experimental time of C-13-NMR quantitative analysis of phenol- for maldehyde resins was reduced so that quantitativeness was maintained. The quantitative spectra of 14 model resins were obtained using a gate d decoupling technique suppressing the NOE. The paramagnetic additive, Cr(acac)(3), was used to shorten relaxation times of carbon atoms. Th e use of Cr(acac)(3) was optimized in two deuterated solvents, DMSO an d acetone. To reach short relaxation times and further the measurement times, the concentration of relaxation reagent, the delay time, and t he number of NMR scans were optimized. Quantitativeness was proved by analyzing the spectra of accurate mixture of model compounds, and the spectra of the condensed model resins. (C) 1998 John Wiley & Sons, Inc . J Appl Polym Sci 69: 1805-1812, 1998.