In this study, we determined the flexural properties and tensile shear strength of five-ply plywood panels produced with eucalyptus (Eucalyptus grandis), beech (Fagus orientalis), and hybrid poplar (Populus x euramericana) using urea-formaldehyde (UF), melamine-urea-formaldehyde (MUF) and phenol-formaldehyde (PF) adhesives. Flexural properties were tested on both parallel and perpendicular to grain samples. Tensile shear-strength tests were conducted on four glue lines of the plywood panels, and the effects of species of trees, type of adhesives, and direction of load were determined. The results of variance analyses showed that the effects of species of trees, direction of load, and type of adhesive on flexural properties were significant, but it was determined by specific flexural properties that the effect of the type of adhesive was based on the density of the plywood. In addition, as a result of findings, it can be said that specific mechanical properties may be a good predictor for comparative studies.
Heat treatment can be used to improve the physical properties and durability of wood. The results achieved by heat treatment can be affected significantly by various factors. Juvenile wood and mature wood from the same trunk have different properties, and the effects of heat treatment on their physical properties have not been well defined. Thus, a study to determine the differences in the physical properties of juvenile wood and mature wood of E. grandis after heat treatment was conducted. Samples of both types of wood were treated at temperatures of 120, 150, and 180 o C for durations of 4, 6, and 8 h. The results showed that the physical properties of juvenile and mature wood, e.g., swelling, moisture content, and fiber saturation point, did not decrease to the same extent. Mass loss of mature wood was higher than that of juvenile wood. Generally, percentage decreases of volumetric swelling, moisture content, and fiber saturation point of juvenile wood were more affected than those of mature wood.
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