Interaction between wood and polyvinyl acetate glue studied with dynamic mechanical analysis and scanning electron microscopy

The long-term properties of bonds are those that are of special interest. To achieve good bonds, the wood polymers and the adhering polymers must be compatible. This paper describes studies of the interaction of wood (Pinus sylvestris) with commercial polyvinyl acetate (PVAc) glue, polymethylmethacrylate (PMMA), and a more hydrophilic acrylate. Interaction was studied with a dynamic mechanical thermal analyzer (DMTA) operating in tensile mode in the tangential direction of wood. DMTA results were correlated with scanning electron microscopy (SEM) fractography studies of adhesion between polymers and wood on a cell wall level. The hypothesis put forward is that a good adhesion on the cell wall level results in a decrease in the glass transition temperature (T,) measured with DMTA. A decrease in T-g for the hydrophilic acrylate was shown when it was impregnated in wood. The decrease of T was correlated with good adhesion to wood on the cell wall level. For PVAc and PMMA no decrease in T g was measured when glued or impregnated in wood. SEM study also showed that the adhesion on a cell wall level was poor. The results show that DMTA can be a useful technique to study adhesion between wood and glue on a molecular level. (C) 2004 Wiley Periodicals, Inc.