Banner for LabNotes
From Lab Notes
Contact Information
Forest Products Laboratory
One Gifford Pinchot Drive
Madison, WI 53726-2398
Phone: (608) 231-9200
Fax: (608) 231-9592


You are here: FPL Home  / Information Products & Services  / Publications

Requested Product

Title: Durable wood bonding with epoxy adhesives

Source: 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 476-478.

Author(s)Frihart, Charles R.

Publication Year: 2003  View PDF »

Category: Journal Articles

Abstract: Although wood was one of the earliest materials to be adhesively bonded, the factors that contribute to strong wood bonds are still not well understood. Wood is a very complex substrate in that it is non-uniform in most aspects. On the macro scale, it is a porous structure with different sized and shaped voids for fluid flow. The structural cells contain four different wall layers, and there is a middle lamella region between the cells. Each cell wall layer is made up of different amounts of three structural components: cellulose, mostly present as a crystalline and rigid polymer; hemicellulose, a mixture of branched carbohydrate polymers; and a matrix of lignin, a crosslinked aromatic polymer. Wood is easy to bond, probably because of its porosity and polar surface. However, few adhesives make a bond that can withstand exterior conditions. With wood, generally the most severe condition involves either stress under wet conditions or cycles of water soaking followed by rapid drying. During a wetting and drying cycle, the wood expands and contracts, whereas most adhesives do not change significantly in volume. Thus, there is a large stress-strain gradient at the wood/adhesive interphase region. Most books and review articles on wood adhesion cover the normal fundamentals of adhesion, but not bond strength. The emphasis is on what takes place at the interface, with discussion of the typical list of chemical interactions that can take place between adhesive and substrate. For bond strength, the interphase regions are also important. Emphasis has been on the preparation of wood surfaces for bonding (1), because it is easy to damage the wood surface so that the surface cells are weak (2). For example, sanding a surface makes it smooth, but pressure from mechanical sanders crushes the surface cells. Planing and knife cutting were found to be the most effective for producing a good surface, with blade angle and sharpness being important factors. Although some adhesives give very durable bonds to wood, epoxy adhesives surprisingly do not. The epoxies are known normally for their good durability. They bond well to plastics, which are less polar than wood, and to metals, which are more polar than wood. The reason that epoxies do not form excellent bonds to wood for exterior applications is not clear. This study provides better insight to factors important to wood bonding and evaluates several models for explaining failure mechanisms of wood bonds.

Keywords: Epoxy resins, adhesives, testing, wood surfaces, surfaces, durability, bonding

File size: 201 kb(s)

This publication is also viewable on Treesearch:  view
RITS Product ID: 11512
Current FPL Scientist associated with this product
Frihart, Charles R.
Research Chemist

Additional items that might interest you
View the video celebrating FPL's 100 years of public service in 2010, from the producers of the Greatest Good....view

Research Highlights from FPL....view

Termite Eradication: A search for the Holy Grail.... view

Moisture Management in Residential Construction Series videos...view

Wood Floor Systems in Residential Construction Series videos....view
- FPL's Mission and Strategic Plan -

FPL's mission is to identify and conduct innovative wood and fiber utilization research that contributes to conservation and productivity of the forest resource, thereby sustaining forests, the economy, and quality of life. ... ..more »

- FPL Research Emphasis Areas -
Advanced Composites

As an integral part of the FPL mission, we improve the long-term sustainability of our Nation's forests by creating valuable composite products from biobased materials ... ..more »

Advanced Structures

The FPL has been in the forefront of wood-frame housing research since 1910 and has long been recognized as a world leader in such housing-related areas as engineered wood ... ..more »

Forest Biorefinery

We all know the compelling reasons that the United States needs to reduce its dependence on fossil fuels. Historically, the greatest increases in energy demand have been for transportation fuels ... ..more »


A leader in wood products research for over a century, the FPL is positioning itself to become the lead Federal research facility for the application of nanotechnology in forest products ... more »

Woody Biomass Utilization

Forests in the United States contain a substantial amount of small-diameter, overstocked, and underutilized material.FPL research projects are exploring the potential of the small-diameter ... ..more »