Analysis of phenol-resorcinol-formaldehyde resins

Abstract

A method based on high-performance liquid chromatography (HPLC) and proton magnetic resonance (PMR) spectroscopy for analyzing phenol-resorcinolformaldehyde (PRF) resins is reported. The equations that describe the number-averaged structures of PRF resins in terms of the PMR absorption intensities of acetylated resins have been derived on the basis of the work of Woodbrey et al. and Anderson et al. The P/R molar ratio of the resin calculated from the PMR intensities was in good agreement with the synthetic P/R molar ratio when correction was made for the loss of phenol evaporated during the drying process that preceded the acetylation. The number-averaged molecular weight (M_n) of the acetylated resin calculated from the PMR intensities agreed with the M_n determined by cryoscopy. Unreacted phenol and resorcinol could be determined by analyzing the water-soluble fraction of the resin by use of high-performance liquid chromatography.