Alkaline PF resins linear extension by urea condensation with hydroxybenzylalcohol groups

Abstract The linear increase of phenol–formaldehyde (PF) resins by reaction under alkaline conditions of the ortho‐ and para‐hydroxybenzylalcohol groups of the PF resin with small molar percentages of urea was followed by model compounds reactions. Apparent rate constants of the reactions of urea with o ‐and p ‐hydroxybenzylalcohols were obtained. Both the ortho‐ and para‐isomerides appeared to react faster with urea than for their autocondensation. The ortho‐isomeride appears to react faster with urea than the para‐isomeride, under alkaline conditions. Autocondensation under alkaline conditions instead appears to be faster in the case of p ‐hydroxybenzylalcohol. The properties of PF resins prepared with the addition of small amounts of urea appear to be consistent with what is observed in the model compounds reactions: Their gel times become faster and viscosity increases with increasing amounts of urea addition. © 1993 John Wiley & Sons, Inc.