On-Site Adhesives Will Not Come from Current Adhesives Manufacturers

A report presented at the University of Wisconsin Institute on Adhesives for Wood and Paper indicated that more economic data was needed on adhesives usage. It was stated that, due to economic pressures, this information was unlikely to come from current adhesives manufacturers and that certain techniques and materials being reported in plastic, chemical, and medical journals could be adapted to wood with little change. Needed is a cheap adhesive with long storage life and low pot life; one that will set immediately in the glue line. A second speaker related wood anatomy to the adhesion problem. A third presentation correlated the factors of materials, application, end use, assembly time, cost (hot-melt adhesives cost 60 to 80 cents per pound but production rates may be 5 times greater than with cheaper urea resins), plant facilities, and specifications. A speech on plywood processing described plywood bonding equipment, stressed the importance of well-cut veneer, and emphasized preparation of logs or bolts for conversion into veneer and the proper set up and maintenance of the veneer lathe or slicer. A new lathe (developed by the Potlatch Forests, Inc., and the Cargate Co.) which features an oscillating knife, was reported to increase cutting speed and improve smoothness of cut. Veneer dryers must not turn out veneer neither overdried nor wet, as both are unsatisfactory for gluing. In a review of splicing operations, an increase in automated layup and the production of overlaid plywood manufactured by a gum process were noted. This report also considered prepressing techniques, their advantages, the principle equipment requirement for prepressing (a hydraulic cold, press), and panel patching operations. One discussion of wood bonding stated that the adhesive (seldom more than one percent of product value) in adhesive-bonded wood products determined operational methods, equipment, and production flow at the plant. Although spraying is used with some adhesives, little work has been done in regard to spraying water-based materials. Curing systems were placed in two categories: absorptive (setting through loss of vehicle) and reactive-setting due to chemical reaction. The uses and properties of adhesives in these groups were then related.

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