Hydroxymethylated Resorcinol Coupling Agent for Enhanced Durability of Bisphenol-A Epoxy Bonds to Sitka Spruce

Abstract

Epoxy adhesives can develop bonds to wood that are as strong as the wood itself, but only if the\nbonds remain dry. Once exposed to repeated water soaking and severe stresses from drying, epoxy\nbonds delaminate and fail to meet requirements for structural wood adhesives intended for exterior\nexposure. A new hydroxymethylated resorcinol (HMR) coupling agent, applied to lumber surfaces\nbefore bonding, chemically couples both epoxy adhesive and lignocellulosics of wood to produce bonds\nto Sitka spruce that are extraordinarily resistant to delamination. In this report, we explain and\ndemonstrate the nature of this coupling agent and the mechanism by which it enhances the durability\nof bonds of a bisphenol-A epoxy adhesive to wood. When diluted with benzyl alcohol, an epoxy\nadhesive developed structural bonds in HMR-primed lumber laminates that met the 5% maximum\ndelamination requirement of ASTM Specification D 2559. The USDA Forest Service has applied for\na patent for this invention.