Assessment of increased wet wood bonding for epoxy-bonded samples using a melamine-urea-formaldehyde priming agent

Abstract

Is the hydroxymethylated resorcinol (HMR) primer unique or can a melamine- based primer also increase the wet wood strength of epoxy bonds? Although the exact reason for poor durability with some wood adhesives is not known, the HMR priming agent was found to facilitate durable bonds in most cases tested. A model of cell wall stabilization that is believed to be the mechanism of HMR has led to the consideration of melamine-based primers. Previous studies have shown that melamine resins can increase the hardness of wood cell walls and lower the amount of swelling from water impregnation. Primer formulations of melamine-urea-formaldehyde (MUF) with various solid contents and bonded using a typical epoxy adhesive (FPL-1A) yielded high wood failure of block shear samples under wet conditions. Untreated samples of the same wood species and conditions had a low percent wood failure and shear strength. The primer was most effective at high dilutions, and performed poorly at concentrations greater than 5 %w/w of the solid polymer. Thus, we concluded that MUF, like HMR, can help create more durable bonds and may be related to modification of the wood cell walls.

Citation

Chandler, Jermal G.; Frihart, Charles R. 2005. Assessment of increased wet wood bonding for epoxy-bonded samples using a melamine-urea-formaldehyde priming agent. Wood adhesives 2005 : November 2-4, 2005 ... San Diego, California, USA. Madison, WI : Forest Products Society: ISBN: 1892529459: pages 99-106.