The curing behavior of resol. III. Effect of alkali metal hydroxides and alkaline earth metal hydroxides as catalyst for the cure of resol

The effect of the addition of cure catalysts on the cure acceleration of ammonia free resol was investigated by means of Curelastometer. The resol which was prepared by the reaction between phenol and formaldehyde with molar ratio 1:1.2 in the presence of NaOH (0.02 mol to phenol) was neutralized with HCI. Catalyst selected from LiOH, NaOH, KOH, Mg(OH)2, Ca(OH)2, Sr(OH)2, and Ba(OH)2 was added to the resol, and curing behavior of the resol was examined. Both alkali metal hydroxides and alkaline earth metal hydroxides accelerate the curing of resol. The cure acceleration effect of barium hydroxide is the largest. In the relation between the kinds of catalysts and the cure acceleration effect, the larger the ion radius of catalyst the faster the cure of resol. Cure speed of the resol containing either sodium hydroxide or barium hydroxide as a curing catalyst increases with an increase in the amount of catalyst. Apparent activation energies of curing behavior of the resols containing the cure catalysts were in the range 17.0–21.3 kcal/mol.