Characterization of substituted phenol–formaldehyde resins using solid‐state carbon‐13 NMR

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Abstract
Crosslinked substituted phenol–formaldehyde resins were synthesized from cashew nut shell liquid, 3‐n‐pentadecylphenol and phenol with formaldehyde. The resulting resins were crosslinked and investigated using carbon‐13 NMR in the solid state using cross‐polarization, magic angle spinning, and dipolar decoupling. Comparisons were made between the spectra of pure phenol–formaldehyde resins and it was shown possible to distinguish between the resins. It was also shown that the proton‐dephased spectrum gave better spectral resolution for the substituted compounds. In addition, the solids carbon‐13 technique verified that the degradation of the substituted phenolic resins occurs first with the degradation of the side chain in agreement with suggestions from earlier work.