Prepolymer resol resins with different phenol/formaldehyde/NaOH molar ratios were synthesized and characterized by technical analysis as well as by 13 C NMR spectra for samples in CD 3 OD solution. Larger amounts of NaOH promoted the binding of formaldehyde and para substitution including the formation of benzoquinone rings with two o, p′-methylene groups in the para position. The polycondensation between ortho-hydroxymethyl groups and one-substituted aromatic para positions as the main thermosetting curing process continued in the heat treatment of resol resins. The self-condensation between ortho-hydroxymethyl groups, the release and oxidation of formaldehyde, and the formation of hemiformals are processes of low significance in curing resol resins. The assignment of 13 C NMR resonances depending on the presence of phenolic hydroxyl groups, phenoxide ions, and substituted quinone rings is discussed.

Prepolymer resol resins with the molar ratio of phenol/formaldehyde 1/2.4 and different amounts of NaOH were synthesized and characterized using 13 C NMR spectra for samples in CD 3 OD solution. Nearly the full substitution in ortho and para aromatic positions occurred, and quite constant ratios of hydroxymethyl/methylene or o, p′/p, p′-methylene groups were obtained. The content of free formaldehyde strongly depends on the NaOH content in synthesis. The prepolymeric chains end mainly with aromatic rings substituted with two ortho-hydroxymethyl groups. The alkali-dependent content of phenoxide ions causes the downfield shifts of 13 C signals for ortho-hydroxymethyl groups from 62.8 ppm to 64.4 ppm and for aromatic carbon bearing the hydroxyl group from 157 ppm to 163 ppm. A comparison with industrial resol resin for the manufacture of plywood is presented.

The structure of oligomers obtained from mono-hydroxymethylphenols in melt condensation at 1208C was determined using 13 C NMR spectra in CD 3 OD solution. Alongside of methylene region of spectrum, valuable information was obtained from signals of aromatic carbons. Noncatalytic conditions promote the formation of dihydroxydibenzyl ethers in equilibrium with ortho-and para-benzoquinones of oxymethylene derivatives. The final methylene linked oligomers are formed, mainly, by splitting the ether intermediates with free aromatic positions. In alkaline conditions, highly nucleophilic phenoxide ions of ortho-hydroxymethyl compounds are responsible for substitution in free aromatic positions. The most favored reaction in the mixture of both hydroxymethylphenols is the formation of p,p 0 -methylene. In condensation of parahydroxymethylphenol, formation of p,p 0 -methylene groups occurs with simultaneous release of formaldehyde. High content of alkali stabilized ortho-hydroxymethyl groups of fully substituted methylene linked oligomers determines the curing behavior of resol phenol-formaldehyde resins. The role of hemiformals in reactions was insignificant.