Relationships between mechanical properties, weight loss and chemical composition of wood during incipient brown rot decay.

Abstract

Incipient decay of wood by brown-rot fungi causes measurable strength losses in wood before measurable weight loss occurs. Previous studies have shown that the high levels of strength loss that occur during incipient brown-rot decay may be related to loss in hemicellulose. This study investigates the effect of decay on hemicellulose composition and the relationship of decay to the mechanical properties of the wood. An in vitro test method was used to allow progressive sampling of southern pine exposed to monocultures of brown-rot fungi. The wood was subsequently analyzed by mechanical testingand chemical analysis. The results demonstrated a ratio of strength to weight loss of approximately 4: I. The chemical data indicated that early strength loss (up to 40%) was associated with loss of arabinan and galactan components. Subsequent strength loss (greater than 40%) was associated with the loss of the mannan and xylancomponents. Significant loss of glucan (representing cellulose) was only detected at greater than 75 percent modulus of rupture loss.