Birch (Betula pendula) is a hardwood which has been used in plywood manufacturing for a long time. The quality of the plywood depends on veneer and plywood processing factors as well as the type of adhesive used. The phenol-formaldehyde (PF) resin was the first synthetic resin used in plywood production and it is still used in the plywood bonding process. The main target of the present study was to evaluate the effect of veneer processing parameters on bond development with PF resin. To evaluate the quality of the adhesive bond in plywood by standard testing methods is laborious and time consuming. This study concentrates on the use of the Automated Bonding Evaluation System (ABES) as an alternative. ABES is miniature hot-pressing device which is equipped with a shear strength testing unit. It is a compact system which allows precise control of the pressing parameters and at same time evaluation of the shear strength properties of the bonds obtained. ABES has been used mainly in studies to characterise the adhesive curing process. The results show that the hydrothermal pre-treatment, drying temperature and the moisture content of veneer has an effect on bond strength development between Birch veneer and PF adhesive.
Keywords: Veneer processing, Phenol-formaldehyde (PF) resin, Bond strength
Authors
M. Piirlaid
Tallinn University of Technology, Tallinn, Estonia
A. Rohumaa
Aalto University School of Science and Technology, Aalto, Finland
M. Matsi
Tallinn University of Technology, Tallinn, Estonia
M. Hughes
Aalto University School of Science and Technology, Aalto, Finland
P. Meier
Tallinn University of Technology, Tallinn, Estonia
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