SOME TECHNOLOGICAL WOOD PROPERTIES OF ALBIZIA MALACOPHYLLA

Abstract

Studies were carried out on wood dimensional stability, density, ash content, natural durability and anatomy of the lesser known Albizia malacophylla so as to improve its utilization potential thus reducing increasing scarcity in hardwood timber supply in Kenya. Wood specimens were exposed to hydrated copper (II) sulphate in a desiccator and dimensional changes evaluated. Wood density was based on oven dry method while ash was generated in a muffle furnace at 525 °C and measured. Extractive content was based on soxhlet extraction using different solvents at different extraction cycles. Natural wood durability against fungi was based on a soil bed test in a laboratory and termite test in the field using AWPA: E7-1993. Thin wood sections were examined for anatomical features using Leica DMLB microscope fitted with EC3 type camera. Wood extracts were subjected to FTIR and GC-MS analysis using standard laboratory procedures. Data was analyzed using statistica Version 7 for windows. Pair wise comparison for dimensional stability and density was done using two sample independent t-tests to test for equality of means while two-way ANOVA was used to test significant difference in means of percentage mass loss between specimens extracted using different solvents and different decay periods. A. malacophylla heartwood is dimensionally stable (5.5%) with less dimensional stable sapwood (9.6%). There was a significant difference (p = 0.000049) between the dimensional stability of heartwood and sapwood. Wood density ranged from 0.84 g/cm3 in sapwood to 1.01 g/cm3 in heartwood while extractive content ranged from 2.35% to 9.71% in heartwood and 2.27% to 4.6% in sapwood. A. malacophylla wood is durable against fungi 8.1% mass loss and very durable against termites, mass loss< 5% reported after 6 months exposure. Results revealed that there was a significant interaction (p < 0.05) between exposure period and the treatments. Heartwood has thin-thick walled wood fibers, exclusively solitary vessels rich in gums and other deposits consistent with the found natural durability. Prismatic crystals were seen as long chains and all ray cells are procumbent. Extractives were found to slow down the growth of fungi under laboratory conditions explaining the observed natural durability. FTIR and GC-MS analysis of crude heartwood extractives indicated presence of aldehydes, ketones carbonyl compounds, esters, aromatic, carboxylic acids and aliphatic carbonyl compounds. Put together, these results indicate that wood from A. malacophylla is a source of valuable biomolecules useful in medical, cosmetic and wood industry. The wood can be a feasible material in construction, furniture and fencing industry where durability is important. Understanding such properties of A. malacophylla provides a basis for a variety of uses both in indoor and outdoor purposes. The research recommends further studies to isolate and identify specific extractive compounds that are responsible for natural durability of A. malacophylla wood.