Inorganic borates such as boric acid, borax, disodium octaborate tetrahydrate, and zinc borate can be incorporated into wood composites such as waferboard to impart decay and insect resistance to the final product. Zinc borate is especially well suited for this application due to its efficacy and leach resistance. The paper summarizes the work performed to date in this area. The effects on strength properties of the composite, water leach resistance of the borate, and effectiveness of the preservative treatment depends on the properties of the borate used and manufacturing variables such as adhesive type and content. In extensive work evaluating the properties of aspen waferboards bonded with pMDI adhesive, we have found that zinc borate performs well as a preservative additive. Such composites have excellent strength and water properties, as well as decay and termite resistance when appropriate levels of adhesive and borate are used. Further work is currently underway to evaluate the performance of zinc borate containing waferboard systems in severe ground contact applications. These types of products might be used in applications traditionally reserved for pressure treated solid wood and plywood.

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