The Chemistry of Wood Strength

Abstract

The source of strength in solid wood is the wood fiber. Generally, cellulose is responsible for strength in the wood fiber because of its high degree of polymerization and linear orientation. Hemicellulose acts as a matrix for the cellulose and increases the packing density of the cell wall. The actual role of hemicellulose in wood strength is unknown, but hemicellulose and lignin are closely associated. Lignin not only holds fibers together, but also holds cellulose molecules together within the fiber cell wall. The chemical components of wood that are responsible for mechanical properties can be viewed from three levels: macroscopic (cellular), microscopic (cell wall), and molecular (polymeric). Mechanical properties change with changes in the chemical environment. Changes in temperature, pressure, humidity, pH, chemical adsorption from the environment, UV radiation, fire, or biological degradation can have significant effects on the strength of wood.