Gluing Pressure-Treated Wood with Resorcinol-Type Adhesives

Gluing of pressure-treated wood was investigated. This paper describes work undertaken to determine the effect pressure treatment of lumber prior to gluing has on the resistance of resorcinol and phenol-modified-resorcinol adhesives to delamination in the 12-day cycle test. The resistance of the glue bond to delamination was determined in this work by a standard ASTM D 1101-50 T vacuum pressure test. The species selected for this study were red oak, white oak, Douglas-fir, and southern yellow pine. All lumber was clear and flat grained. It was kiln-dried to a moisture content of 12 percent. The following preservatives were used to pressure treat the four species listed above: creosote, pentachlorophenol, copper naphthenate, acid copper chromate, ammoniacal copper arsenite, copperized CZC, chromated zinc chloride, chromated copper arsenate, and Tanalith. All specimens were pressure impregnated in accordance with American Wood Preservers’ Association Standard C-2. Preservative retentions are listed. Preparation of pressure-treated lumber for gluing was similar to that normally used for untreated wood. As with untreated wood, clean surface was required. This was obtained by planing approximately 1/16 inch from each surface to be glued, not less than 2 hours or more than 6 hours before spreading the adhesive. Spreading was done in a constant temperature-humidity room where the wood and the glue mix were kept at 75?F. before and during the spreading. A torque wrench was used to measure the desired pressures. The adhesive was cured for 2 hours at a glue-line temperature of 150?F. Time of cure was increased to 6 and 10 hours when satisfactory bonding was not obtained after a standard 2-hour curing cycle. Testing followed the procedures outlined by ASTM D 1101-50T procedure for three-cycle testing. The data indicate that commercially treated wood employing nine preservatives and four species can be adequately bonded with resorcinol or phenol resorcinol adhesives. With certain treatments and certain woods (acid cupric chromate on white oak and southern yellow pine; ammoniacal copper arsenite on white oak, southern yellow pine, and Douglas-fir; and chromated copper arsenate on white oak), curing at 150?F. glue-line temperature for longer than 2 hours is necessary for adequate bonding. The resorcinol and phenol modified-resorcinol adhesives which were tested bonded preservative- and fire-retardant-treated woods very well. The straight resorcinol adhesives have slightly greater applicability.

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