Progress in Glues & Gluing Processes

Urea glues continued to be the workhorse of the wood gluing industry during the 2-year period (1960-61) because of their versatility, low cost, and freedom from color. New copolymers were used to improve the resistance of polyvinyl-resin glues to deformation at elevated temperatures. No particular changes occurred with other major adhesive types used for wood although a drop in the cost of phenol encouraged some plywood manufacturers to undertake their own production of phenol-resin glues. Rotary presses have gained popularity as pressure type or rubber-based adhesives are, used to, bond polyester or other films to wood panel products. Air operated mixing and dispensing equipment are helping industry apply highly reactive adhesive systems such as polyesters, epoxies, or polyurethanes to wood processing. Two improvements in end jointing of lumber included adoption of a new cutterhead for sharper, stronger finger joints and a University’s announcement of a promising die-pressed finger-jointing process. Quality control programs for glued products were undertaken by the Western Pine Association for lumber and by Plywood Fabricators Service for prefabricated plywood components. The Federal Housing Administration issued materials releases on glued products such as end jointed studs and laminated roof decking. A prototype machine was developed to aid quality control by rapidly proof testing glued end joints in lumber. The softwood plywood industry faced some gluing problems with : 1) veneer dried in direct fired driers at temperatures exceeding 425?F, 2) western larch veneer due to surface deposits of the extractive galactan, and 3) the dense summerwood in Douglas-fir veneer from southern Oregon. The trend to prepressing has continued. One advantage cited was a saving in glue through improved wet transfer and penetration. Urea has continued as the overwhelming choice as a binder for particleboard but interest has remained in phenol-resin binders that would permit particleboard to endure severe service requirements. Fifty-eight references were cited in the review of progress; an additional 63 references were listed.

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