DIMENSIONAL STABILITY OF NINE TROPICAL HARDWOODS FROM CAMEROON

Abstract

This study investigated the rate of swelling and dimensional stability of nine tropical hardwood species from Cameroon, namely, ayous (Triplochiton scleroxylon), bilinga (Nauclea diderrichii), bubinga (Guibourtia tessmannii), iroko (Chlorophora excelsa), makore (Mimusops heckelii), moabi (Baillonella toxisperma), movingui (Distemonanthus benthamianus), teak (Tectona grandis) and zingana (Microberlinia brazzavillensis). Continuous swelling of wood specimens immersed in water at room temperature for up to a maximum of 48 hours were monitored using linear voltage displacement transducers (LVDTs). The amount of water uptake as function of immersion duration was measured and correlated with wood porosity. Among the species used in this study, teak showed the lowest swelling rate, therefore, the more dimensionally stable property. Ayous, iroko and movingui were relatively more dimensionally stable than bubinga, makore and moabi. The swelling rate in the tangential direction was much higher than the radial. Bubinga, bilinga and zingana exhibited higher radial swelling rates compared with iroko, teak and makore. Similarly, higher tangential swelling rates were obtained for bubinga and movingui in comparison with teak, makore and moabi. The calculated ratios of the tangential to radial swelling rates also known as the anisotropy of the species used in this study were within the normal range and in agreement with published data. In conclusion, dimensional stability of some tropical species can be estimated with a 48-hour swelling test. Long-term and field data are needed to confirm the validity of this test.