Water Imbibition Capacity of Some Nigerian Timbers: A Function of Wood Density and Structure

Abstract

Wood is a heterogeneous, hygroscopic, cellular and anisotropic material of biological origin. The properties of wood that make it an ideal raw material for several purposes are mainly determined by the specific architecture of the cell walls. Moisture content, porosity and water imbitition capacity contribute to the quality of timber. The examination of the internal microscopic structure of the timber samples will be done by Scanning Electron Microscopy (SEM). Of the fifty-three timbers studied, thirty-two were of medium density (0.403 ± 0.020 to 0.715 ± 0.011 g/cm 3) , ten were of low density (0.256 ± 0.008 to 0.380 ± 0.012 g/cm 3) and eleven were quite dense (0.784 ± 0.020 to 1.111 ± 0.039 g/cm 3), with Ricinodendrom heudelotti having the least value and Irvinga smithii, the highest. Water imbibitions capacity after 24 hours was quite high for Ricinodendrom heudelotti and Ceiba pentandra while that for Irvinga smithii, Lophira lanceolate, Khaya senegalensis and Erythrophleum suaveolens were low. There was an inverse relationship between the maximum moisture content of these wood samples and their density. The scanning electron micrographs of selected timbers present ring-porous hardwoods as well as diffuse-poruos hardwoods.Fibrous nature of Entradrophragma utile and Hollarhena floribunda may account for their high moisture content (MC) values while the spherical granules in Tetrapluera tetraptera are suspected to be hydrophobic since the water imbibition capacity observed after 24h was lower than those of similar density.