Characterization of PVAc Adhesive Penetration and its Effect on Wood Properties

Abstract

Penetration of adhesive into the wood cell and lumens is an important factor that may enhance the durability of the adhesive bonds. In this study, the diffusion of adhesive polyvinyl acetate (PVAc) into the cell wall of various types of wood was evaluated making use of micro-CT. Compression shear block tests were also applied to examine the mechanical performance of the bond. In adhesive assemblies examined, cell walls at the immediate surface which were damaged during machine planning were full of adhesives. As the penetration of PVAc increased, the variation in the observed bind strengths was not substantial. Bonded with the same type of glue, black spruce appeared to have lower shear strength than Douglas fir and lodgepole pine. Moreover, gravity seemed to play a role in the glue penetration. During clamping and adhesive curing, the substrate on the lower of the shear block specimen had a deeper glue penetration. There are some correlations between glue penetration and glue line thickness measured using micro-CT.