Gluing Characteristics of Treated Sweetgum Veneer

To examine the effect of preservative types and retentions on the effectiveness of three common adhesives, a study was made using sapwood veneer from one single sweetgum tree. Sapwood of sweetgum is a highly treatable and highly gluable veneer and is used in the furniture industry. Four waterborne salts at four retention levels were used to prepare the veneers. These were sodium pentachlorophenate, Celcure, Chem-mite, and Boliden salts. The retentions were 3.0, 1.5, 0.75, and 0.38 lbs./cu.ft. The adhesives were phenol formaldehyde, phenol-resorcinol formaldehyde, and melamine formaldehyde. All bonds with all three types of adhesives at the two lower retentions of all treating chemicals were acceptable with reference to bond strength. Bonds with acceptable percentages of wood failure were mostly from this group also. In general, the deleterious effect of treatments was increased by higher treatment concentrations. The strongly acidic or alkaline treatments with Celcure and Boliden salts produced poorest bonds. Dry, bond, strength reductions over the controls were: Celcure (24 percent), Boliden salt (16 percent), Chemonite (10 percent), and sodium pentachlorophenate (3 percent). Generally 1.0 lb. /cu.ft. is enough retention to meet commercial specifications for lumber. The more uniform penetration feasible for veneer should permit effective protection at lower penetrations. If so, well-protected plywood, glued after treatment, should be feasible for normally gluable and treatable veneer.

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