Estimating Durability of Wood Adhesives in Vitro

Samples of urea-formaldehyde, melamine-urea formaldehyde, phenol-formaldehyde, phenol-resorcinol formaldehyde, and melamine-formaldehyde adhesives were mixed according to manufacturers instructions, cured 7 hours at 70?C in culture dishes and ground to minus 40 mesh. These were then subjected to hydrolysis at reflux in distilled water, 0.1 N sulfuric acid, and 0.1 N ammonium hydroxide. Acid hydrolyses were also done at 40?C and 70?C. Maximum total hydrolyzable formaldehyde was 41 percent for urea, 35 percent for melamine-urea, and 29 percent for melamine, all in 0.1 N sulfuric acid at reflux; 3.6 percent for phenol in distilled water at reflux, and less than 0.1 percent for phenol-resorcinol, regardless of the hydrolysis conditions. This ranking agrees closely with adhesive durabilities reported in the literature and supports the theory that durability is related to hydrolysis resistance.

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