Compatibility of nonacidic waterborne preservatives with phenol-formaldehyde adhesive

Thirteen nonacidic waterborne preservatives were investigated for their compatibility with phenol-formaldehyde adhesive on aspen veneer treated with the preservatives to retentions of 0.2, 0.4, and 0.6 pcf. Of these preservatives, didecyl dimethyl ammonium chloride (DDAC), DDAC with copper, DDAC with carbamate (DDACCA), sodium fluoride, and ammonium hydrogen difluoride did not interfere with adhesion at any retention level. Carbamate in the DDACCA preservative apparently reinforced interfacial regions of the bondline to produce bond strengths much higher than those of untreated controls, particularly at the higher retentions. Ammoniacal copper zinc arsenate at 0.2 pcf retention did not interfere with adhesion, but at higher retention levels bond integrity was below standards. All three borated preservatives that were studied caused poor bonding, even at the lowest retentions. Emulsions of copper naphthenate, copper octoate, and zinc naphthenate also caused poor bonding. Determination of wet wood failure after vacuum-pressure soaking was more effective in detecting adhesion incompatibility than determination of dry shear strength and wood failure after multiple cycles of vacuum-pressure soaking and drying.

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