Scanning electron microscopy was used to study the structural changes occurring in Kempas (Koompassia malaccensis Maing. ex Benth) exposed to the weather in tropical (Malaysia) and warm temperate (Canberra, Australia) environments. Similar structural changes took place in both environments, but degradation occurred more rapidly in Malaysia. Furthermore in Malaysia the weathered wood surface was rapidly colonised by staining fungi. A bioassay showed that one such fungus was capable of degrading the wood. Shear and cross-cut tape tests were used to measure the adhesion of a clear finish on Kempas weathered in both Malaysia and Canberra for periods of 5 to 40 days. Degradation of wood during weathering reduced the adhesion of the clear finish and there was a significant loss of adhesion on specimens weathered for 5 days. Adhesion was lower on wood specimens weathered in Malaysia than on those weathered in Canberra. For example, the overall mean shear adhesion of the clear finish on specimens weathered in Malaysia was 5.27 Nmm2 compared to 6.76 Nmm2 for specimens weathered in Canberra. A similar trend was noted for the area of clear finish removed from specimens during tape testing. Thus, the overall mean area of clear finish removed from specimens weathered in Malaysia was 34.1 mm2 compared to 29.7 mm2 for specimens weathered in Canberra. The practical implications of these findings for the finishing of exterior wood in tropical environments are briefly discussed.
Key words: Kempas, weathering, tropical, warm temperate, structural changes, clear finish, adhesion.
Correspondence: Ahmad Shakri Mat Seman, Department of Forestry, The Australian National University, Canberra, ACT 0200, Australia
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E-mail: ahmad.shakri@anu.edu.au