15 - Properties and utilization of wood

Abstract

Wood technology deals with the physical appearance, anatomical structure, and mechanical and chemical properties of wood. All these features affect wood figure, strength, shrinkage patterns, and deformation. The physical properties of wood are derived from its particular molecular constitution, its cell wall organization, and the interaction of its structural units. External influence such as water content, shrinkage, and swelling, which may cause warping and checking, also affect the physical properties of wood. Weight is controlled by two major variables: the amount of solid cell wall material present and the quantity of water in the sample. Water is located in wood as bound water in the cell wall and as free water in the numerous spaces of the cell lumina and intercellular cavities. As the walls of individual cells lose water, they become thinner, and shrinkage of the wood occurs. Due to the stresses that are incurred in different directions by individual wood cells during the drying process and the complicated patterns of shrinkage that result, dried lumber tends to warp. The mechanical properties of wood are the multitude of measurable expressions that result from applied forces. These include strength properties, stiffness, elasticity, hardness, and toughness.