INVESTIGATION OF A RESORCINOL FORMALDEHYDE RESIN BY C-13-NMR SPECTROSCOPY AND INTRINSIC-VISCOSITY MEASUREMENT

Various molecular weight fractions and oligomers isolated from a novolac type resorcinol-formaldehyde (RF) wood adhesive resin were studied by C-13-NMR, gel permeation chromatography (GPC), and intrinsic viscosity measurements. The C-13-NMR results indicate that methylene groups occur mostly between C4-C4' and C2-C4' carbons and in minor amounts between C2-C2 carbons of resorcinol rings. By suppressing the nuclear Overhauser effect (nOe) and using a long delay time for C-13-NMR measurements, reasonable methylene/aromatic carbon ratios were obtained from the aromatic C1 carbon patterns that have resulted from different numbers of methylene groups bonded on the aromatic ring. This analysis results indicate that the RF resin has an appreciable amount of branch structures and compare favorably with the gel permeation chromatography and intrinsic viscosity measurement results.