Effects of Acacia mangium bark extracts on dimensional stability, termite resistance, and fungal decay resistance of rubberwood

Abstract

Wood bark is a source of extractives with potential for valorization based on their chemical functionalities. In this study, Acacia mangium bark was extracted with distilled water. Then bark extract solutions in distilled water at various concentrations (5%, 10%, 15%, and 20% w/w) were vacuum impregnated into rubberwood. The color of the impregnated rubberwood was observed. The retention of bark extract in rubberwood and weight percent gain (WPG) from it were calculated. The morphology, dimensional stability, resistance to fungal decay, and subterranean termite resistance were determined for impregnated rubberwood samples. It was found that a higher concentration of bark extract gave higher retention and WPG in vacuum-impregnated rubberwood. The color of impregnated wood got darker with the concentration of bark extract, from light brown to red brown and dark brown. The bark extract penetrated all the way to the center (in thickness direction) of the wood and remained in lumens of vessels, parenchyma, and ray cells. The bark extract can improve dimensional stability of rubberwood. Weight loss caused by the fungi Trametes versicolor and Gloeophyllum striatum decreased with retention of bark extract in the impregnated wood. The bark extract may be toxic to termites (Coptotermes gestroi) that consumed impregnated wood: termites died during the third and fourth weeks after they attacked wood impregnated with bark extract at 15% or 20% concentration.