Effect of pH and buffering capacity of wood on the gelation time of urea-formaldehyde resin.

The pH and buffering capacity for water extract of the heartwood and sapwood of ten hardwoods and nine softwoods were determined. pH values ranged from 4.00 to 5.86 for hardwood and 4.02 to 5.82 for softwood. The gelation time for a urea-formaldehyde resin as affected by wood flour for each wood was determined. Analysis shows that a strong correlation between gel time of wood flour and either pH or acid buffering capacity of water extract exists.