Coupling agent improves durability of PRF bonds to CCA-treated southern pine

Today’s wood products market lacks adhesively bonded, structural lumber products that have been treated with chromated copper arsenate (CCA) preservatives. The problem arises, in part, because commercial adhesives do not adhere to CCA- treated wood well enough to consistently meet rigorous standards for resistance to delamination. A new hydroxymethylated resorcinol coupling agent, when used as a dilute aqueous primer on lumber surfaces before bonding, physicochemically couples phenol-resorcinol-formaldehyde (PRF) adhesives to lumber surfaces of CCA-treated southern pine. In this study, two commercial PRF adhesives met the 5 percent maximum delamination requirement of ASTM D 2559 on southern pine treated with CCA to 0.4 and 0.6 lb./ft.3 (6.4 and 9.6 kg/m3) retention levels. The USDA Forest Service has applied for a patent covering this invention.

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