Thermolysis of orthonovolaks. II. Phenol–formaldehyde and α‐naphthol–formaldehyde resins

A series of α-naphthol-formaldehyde orthonovolak resins were synthesized by altering the mol ratios of α-naphthol and formaldehyde involved in the condensation reaction. Oxalic acid was used as the catalyst. The softening temperatures and thermal degradation behavior of these resins are presented. Thermal degradation kinetics of these resins were investigated by applying nonisothermal integral methods of Coats–Redfern and Horowitz–Metzger. The dynamic thermogravimetric experiments were conducted in air to obtain differential ther-mogravimetric (DTG) plots. The ratio of the partial integrated area at temperature T to the total area was used to estimate the fractional degradation in the analysis. Degradation proceeded in two stages. The second stage was the predominant one. The thermal degradation profile and activation energies in this stage are discussed in relation to orthonovolaks of similar composition based on phenol–formaldehyde. © 1993 John Wiley & Sons, Inc.