Influence of prefreezing on the mechanical response of wood to high temperature drying

Abstract

There are often a number of issues associated with high temperature drying of wood, the most important of which is the reduction in some mechanical properties. This study investigated the potential of freezing pre-treatment in combating this potential problem. Freezing of birch (Betula pubescens) wood was done inside a refrigerator at –20°C for 90 hours followed by high temperature drying at 120°C. The modulus of elasticity and modulus of rupture were determined. Pre-freezing reduced the degrading effects of high temperature drying on the strength wood in the radial direction while no significant effect occurred in the tangential direction. In the radial direction, the effect is more pronounced on the modulus of elasticity than the modulus of rupture. The limitation of the significance of pre-freezing to the radial direction suggests that there is more improvement in cell rigidity resulting in higher resistance to the harmful effect of high temperature drying in the radial direction than in the tangential direction.