Adhesive interactions with wood

While the chemistry for the polymerization of wood adhesives has been studied systematically and extensively, the critical aspects of the interaction of adhesives with wood are less clearly understood. General theories of bond formation need to be modified to take into account the porosity of wood and the ability of chemicals to be absorbed into the cell wall. Sufficient penetration is important for good bond formation, but it is not clear whether the penetration into lumens or the cell wall is more critical. For the bond forming process, thermodynamic wetting and viscosity are critical, but viscoelastic energy dissipation is important for the debonding process. The interphase formed during bond formation should influence the bonded assembly's ability to dissipate the internal and external stress during use, but the exact relationship is not clear. Studying of the bonding and debonding processes can be broken down into examination on the millimeter, micrometer, and nanometer spatial scales. The millimeter and larger scale is what is used for typical evaluations. However, the micrometer scale plays an important role because this scale relates to the cross-sectional size of cells that are the basic structural unit of wood. In this study, models are proposed for the adhesive--wood interphase that would reduce the stress concentration between the wood and the adhesive as the dimensions of the wood vary with changes in the wood moisture content. The nanometer scale is important because it relates to the interaction of the adhesive with the wood on the scale of the cellulose fibrils and the hemicellulose and lignin domains. The internal and external forces on the adhesive wood bond vary considerably for different products, such as laminated lumber, plywood, oriented strandboard (OSB), and fiberboard. A better understanding of the critical aspects of the adhesive--wood interaction should lead to a more efficient development of improved adhesives. 2004 This article is in PDF format (file size: 8129 kb). To download this article, right click on the link immediately below and choose "save target as". To view the article, left click the link immediately below.
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Adhesive interactions with wood   (2004)

While the chemistry for the polymerization of wood adhesives has been studied systematically and extensively, the critical aspects of the interaction of adhesives with wood are less clearly understood. General theories of bond formation need to be modified to take into account the porosity of wood and the ability of chemicals to be absorbed into the cell wall. Sufficient penetration is important for good bond formation, but it is not clear whether the penetration into lumens or the cell wall is more critical. For the bond forming process, thermodynamic wetting and viscosity are critical, but viscoelastic energy dissipation is important for the debonding process. The interphase formed during bond formation should influence the bonded assembly's ability to dissipate the internal and external stress during use, but the exact relationship is not clear. Studying of the bonding and debonding processes can be broken down into examination on the millimeter, micrometer, and nanometer spatial scales. The millimeter and larger scale is what is used for typical evaluations. However, the micrometer scale plays an important role because this scale relates to the cross-sectional size of cells that are the basic structural unit of wood. In this study, models are proposed for the adhesive--wood interphase that would reduce the stress concentration between the wood and the adhesive as the dimensions of the wood vary with changes in the wood moisture content. The nanometer scale is important because it relates to the interaction of the adhesive with the wood on the scale of the cellulose fibrils and the hemicellulose and lignin domains. The internal and external forces on the adhesive wood bond vary considerably for different products, such as laminated lumber, plywood, oriented strandboard (OSB), and fiberboard. A better understanding of the critical aspects of the adhesive--wood interaction should lead to a more efficient development of improved adhesives.

Author: Frihart, Charles R.

Source: Fundamentals of composite processing : proceedings of a workshop, November 5-6, 2003. Madison, WI : U.S. Department of Agriculture, Forest Service, Forest Products Laboratory, 2004. General technical report FPL ; FPL-GTR-149: Pages 29-38

Citation: Frihart, Charles R.  2004.  Adhesive interactions with wood  Fundamentals of composite processing : proceedings of a workshop, November 5-6, 2003. Madison, WI : U.S. Department of Agriculture, Forest Service, Forest Products Laboratory, 2004. General technical report FPL ; FPL-GTR-149: Pages 29-38.