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Improved understanding of moisture effects on outdoor wood–adhesive bondlines

Author(s):

Year:

2017

Publication type:

General Technical Report (GTR)

Primary Station(s):

Forest Products Laboratory

Source:

Gen. Tech. Rep. FPL–GTR–246. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory. 9 p

Description

The development of improved moisture-durable wood adhesives for outdoor applications, such as repairing historic covered bridges, is hindered by an incomplete mechanistic understanding of what makes a wood–adhesive bond moisture-durable. The wood–adhesive bondline is extraordinarily difficult to study because of the chemical, structural, and mechanical complexities and variations of the wood substrate and the many potential interactions that can occur between the wood and adhesive to enhance or degrade the bond performance. Although the literature is filled with bonding information from the bulk level, sufficient experimental tools to study wood–adhesive bondlines and the effects of moisture on bondlines at the cellular and subcellular levels are lacking. Therefore, we recently developed tools to study bondlines at these size scales. We have used synchrotron-based micro x-ray fluorescence microscopy (μXFM) and micro x-ray computed tomography (μXCT) to map the penetration of adhesive into the wood anatomical structure. We also developed nanoindentation into a tool capable of assessing the effects of moisture and adhesive infiltration on wood cell wall properties. Using custom-built in situ humidity chambers with μXCT and small angle neutron scattering, we can now study the moisture-induced swelling in wood across the relevant length scales in bondlines that span from the millimeter to nanometer length scales. Finally, we developed a new approach to study moisture-induced swelling forces using wood slivers. This report gives an overview of these recently developed techniques. The insights these tools provide toward understanding moisture durability in wood adhesive bondlines are also discussed in this report.

Citation

Jakes, Joseph E.; Plaza, Nayomi Z.; Arzola Villegas, Xavier; Frihart, Charles R. 2017. Improved understanding of moisture effects on outdoor wood–adhesive bondlines. Gen. Tech. Rep. FPL–GTR–246. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory. 9 p.

Cited

Publication Notes

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https://www.fs.usda.gov/treesearch/pubs/54438