The effects of drying temperatures on preservative retention and penetration of some Malaysian fast-growing species timbers

This study was conducted to investigate drying properties of some Malaysia fast-growing species timbers exposed to drying under different temperatures, and evaluated the effects of these drying temperatures on preservative retention and penetration of the dried timbers. Four Malaysian fast-growing species, namely acacia (Acacia mangium), rubberwood (Hevea brasiliensis), sentang (Azadirachta excelsa), and kelempayan (Neolamarckia cadamba) obtained from a local plantation in Kelantan, Malaysia were used in this study. Drying specimens with dimension of 30 x 150 x 500 mm were dried under air-drying condition, a constant temperature of 60, 80, 100, and 120 degrees C until the moisture content of the specimens reaches an equilibrium moisture content at each drying condition. The drying properties of the specimens were then examined. After drying, stick specimens with a dimension of 20 mm (radial) x 20 mm (tangential) x 110 mm (longitudinal) obtained from the heartwood of the drying specimen were immersed in cupper azole (CuAz) wood preservative solution for 10 minutes under normal atmospheric pressure for rubberwood and kelempayan, and 30 minutes for acacia and sentang. Retention and penetration of the specimens were evaluated. The results confirmed that drying temperature had a significant effect on drying time. Drying under air-drying condition demanding considerable time, particularly drying acacia and sentang under air-drying condition required longer drying time than the other timber species. Drying temperature also had significant effects on preservative retention of all timber species, except kelempayan. The results demonstrated that preservative retention of all timber species tends to increase as drying temperature increased. In addition, high-temperature drying gives a positive effect on preservative penetration. Drying acacia under temperature of 100 degrees C could maintain a higher percentage of preservative coverage area until a sufficient depth from the penetration surface. This finding suggests that high-temperature drying is more desirable for better preservative retention and penetration of the specimens used in this study.