The Effect of Wood Extractive Content on Glue Adhesion and Surface Wettability of Wood

Ralph M. Nussbaum, Magdalena Sterley

Abstract


The effect of wood extractive content on glue adhesion and surface wettability was evaluated. Specimens of pine heartwood (Pinus silvestris), stored at different times after surface planing, were assembled with a water-resistant polyvinyl acetate glue. The test material was classified according to its content of lipophilic extractives by chemical analyses. Glue adhesion parameters were assessed using two different test methods, a standard ASTM shear strength test and a nonstandard fracture test. Surface wettability was evaluated by contact angle measurements in parallel experiments. The results showed that, when the strength of the bonds was determined, the percentage adhesion failure increased with increasing extractive content for specimens exposed to water boiling test; but no such correlation was found in tests without water boiling. The correlation between glue bond strength and extractive content was poor. Surface storage time had no significant effect on the glue adhesion parameters. Surface wettability measurements revealed a complex relationship between extractive content and surface storage time.

Keywords


Adhesion;extractives;glue;softwood;wettability;wood

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