Curing of resole‐type phenol–formaldehyde resin

Abstract The process of resole‐type phenol–formaldehyde resins was studied by differential thermal analysis and infrared spectroscopy. It was shown that in neutral media the first reactions that occur are those between free phenol present in the resin and monosubstituted methylol phenol with free reactive positions on the benzene ring. The formation of methylene linkages is followed immediately by the condensation of methylol groups to give dibenzyl ether linkages. These are subsequently destroyed at about 210°C. It is believed that the entire curing process is governed by a free‐radical mechanism. It is also shown that oxidation of the resin occurs slowly at room temperature and humidity.