Interaction of copper wood preservatives and adhesives

Abstract

Compared to other substrates, wood is generally easy to bond. However, adhesion is diminished when the wood surface is covered by chemicals, whether natural oils and resins or added chemicals. Among the chemicals added to wood are fire retardants and wood preservatives. Chromated copper arsenate (CCA) has been widely used to protect wood against rot and termites, but concern about the toxicity of arsenic is leading companies to turn to other treatment chemicals (1). The two most prominent chemicals for replacing CCA in treating wood are ammonical copper quat (ACQ) and copper azole (CAz). Most treatment chemicals tend to reduce the strength of wood bonds (2). In fact, the bonds of CCA-treated wood have been found to be less durable than those of untreated wood (3). The lack of adhesion is usually revealed by an environmental resistance test, which is critical since preservative-treated wood is often exposed to water. Exposure to water and drying is a severe test for wood adhesion since the bond has to withstand the expansion and shrinking that occurs when the wood picks up and loses moisture content, as well as the thermal expansion and contraction of the wood (4). The reduced adhesion of treated wood can be the result of a number of factors. For example, nodules of CCA on the wood surface can limit adhesion (5). However, treatment with CCA does not accelerate the cure of the adhesive (6). There is little in the literature on bonds of ACQ-and CAz-treated woods.

Citation

Frihart, Charles R. 2003. Interaction of copper wood preservatives and adhesives. Proceedings : 26th Annual Meeting of the Adhesion Society, Inc. : Adhesion Fundamentals : from Molecules to Mechanisms and Modeling : February 23-26, 2003, Myrtle Beach, SC. Blacksburg, VA : The Adhesion Society, c2003: pages 244-245.