effects of extractives on THE dynamic water swelling behaviour and fungal resistance of Malaysian hardwood

Effects of extractives on the dynamic water swelling properties and fungal resistance of Malaysian tropical hardwood species, namely, sesendok (Endospermum malaccense), acacia (Acacia mangium) and chengal (Neobalanocarpus heimii) were determined. They exhibited extractive contents of 3.2, 7.5 and 24.9% respectively. During the swelling test, an induction period occurred at the initial stage. The swelling kinetic behaviour was non-linear throughout the entire process, especially for sesendok. Chengal, which had the highest extractive content, exhibited greater equilibrium swelling but lower swelling rate. Removal of extractives apparently resulted in increase in both the equilibrium swelling and swelling rate presumably due to easier access of water to the wood cell wall. Throughout the 48-hour immersion period, chengal in the tangential direction exhibited double component swelling profile. After incubation with brown- and white-rot fungi, the extracted chengal exhibited considerably higher mass loss than the non-extracted samples. A distinct difference in the decay behaviour of non-extracted and extracted chengal might be attributed to hydrophobic characteristics and cell wall bulking effects imparted by the extractives.