First Replications Comparing Bond-Degrade-Accelerating Systems

This is the second paper of a series designed to study bond degrade accelerating tests (BDA). Eleven different BDA test specifications were studied. These involved steaming or water soaking often with a high-temperature drying cycle. One system used a freeze cycle in the midst of steaming, soaking, and drying. Periodically, plywood shear tests were carried out on specimens undergoing tests which provided a measure of bond degrade as a function of duration of BDA exposure. It was hoped that some of the BDA systems would rank the 10 glues in the same order of durability that the glues are known to exhibit in actual field service. Glues included a phenolic, phenolic-resorcinol, melamine, melamine-urea, interior-grade phenolic, an exterior PVA, urea, blood, casein, and soya. Response was measured as breaking load vs. duration of exposure fitted with an equation by least squares. The comparative response was days exposure required to degrade to a breaking load of 100 pounds which could be computed by interpolation or extrapolation of the regression equation. The results from tests at three different laboratories were compared for the 10 glues and 11 BDA systems insofar as the data available permitted. The results obtained in this study showed that one system (BDA3, continuous soaking in boiling water) ranked all glues in the identical order or within one rank of that order of durability established by field experts from years of experience. BDA1 (continuous saturated steam), BDA6 (repetitions of soaking in boiling water for 4 hours, drying at 142?F for 20 hours), and BDA11 (PACO microbe-box treatment) gave identical rankings to seven of the glues and BDA2 (continuous soaking in water at 142?F) and BDA8 (continuous soaking in water at 72?F) gave identical rankings to five of the glues.

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