DEVELOPMENT AND OPTIMIZATION OF FAST QUANTITATIVE C-13 NMR CHARACTERIZATION METHODS OF NOVOLAC RESINS

An improved C-13 NMR quantification technique of random and high-ortho novolacs in THF-CDCl3 solutions is reported. Full quantitative spectr a of phenol formaldehyde resins with high signal-to-noise ratios are o btained by using chromium acetylacetonate under optimized spectral con ditions within a few hours of spectrometer time. Attached proton test (APT) spectra were acquired to enable proper peak assignments in the r egion with significant overlap. For several novolacs, prepared under d ifferent catalytic conditions, the degree of polymerization, degree of branching, number average molecular weight, isomeric distribution, an d number of unreacted ortho and para phenol ring positions could accur ately be determined. The improved quantification method and the use of the aromatic instead of the aliphatic region permitted to measure for the first time small differences in network parameters for comparable novolac samples.