Evaluation of Resin Adhesives

Adhesives tested in this study included urea formaldehyde, fortified urea formaldehyde, phenol formaldehyde, resorcinol formaldehyde, phenolic, resorcinol-paraformaldehyde, and resorcinol-aqueous formaldehyde. Test pieces included three-ply 1/16 and 1/8 inch veneer panels. One test compared three-ply 1/8 inch veneer plywood (cross ply) with parallel grain laminates of the same size. Laboratory tests included the standard shear tests, a dry strength determination at 8 to 10 percent moisture content, five cycles of a 16-hour immersion in water followed by 8 hours of drying at 140?F., and five soak-dry cycles of a 4-hour boil and 20 hours of drying at 140?F. Results of these tests are given in table form. Outdoor exposure testing of larger but similarly constructed pieces was done, and the results were evaluated With dry shear tests and recording edge delamination. More laboratory tests are needed to provide realistic information on resin degradation caused by exposure to water, humidity, and temperature. Test specimens showed failure under simulated environmental conditions, while similar pieces in actual use have failed.

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