Softening Temperature, Ash Content, and Bond Quality of Polyvinyl-Acetate-Emulsion Adhesives

Twenty-nine commercial polyvinyl-acetate-emulsion adhesives with ash contents ranging from 0.11 to 16.56 percent were examined for their bonding ability with wood and, subsequently, for the quality of wood-adhesive bonds at elevated temperatures. Strength retention of wood-adhesive joints at elevated temperatures was found to depend greatly on ash content of the adhesives. The adhesives with ash content between 3 and 8 percent retained far more strength than those with ash content of less than 1.5 percent in the 160 to 220?F (71 to 104?C) range. The better heat resistance of high-ash-content adhesives was, explained by a good linear relationship between softening temperature and ash content of the adhesives. Thus, determination of softening temperature is an effective technique for evaluating heat resistance of PVA and wood joints.

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