Inter-family variation in fibre dimensions of six tropical hardwoods in relation to pulp and paper production.

Fibre characteristics determine utilization potentials of timbers. Fibre dimensions influence wood pulpability, durability and physico-mechanical properties. Fibre length, width, lumen width and wallthickness of six tropical timbers from three families (Meliaceae, Sterculiaceae and Ulmaceae) were investigated from heartwood splinters (20×2×2mm) de-lignified in 1:1 glacial acetic acid and hydrogen peroxide [at 600C], teased out and stained. Fibre lengths range from 0.79mm for Holoptelea grandis (Ulmaceae) to 1.88mm for Khaya ivorensis (Meliaceae) similar to the mean (2mm) for tropical hardwoods and pulpable length (0.65-1.2mm). The Meliaceae has moderately long fibres (1.61mm) but medium-sized for Ulmaceae (1.19mm) and Sterculiaceae (1.59mm). Cedrella odorata (Meliaceae) has wide fibres (36.5μm) and lumina (27.6μm), Celtis milbraedii (Ulmaceae) has narrow fibres (17.49μm) and lumen (8.97μm), all within pulpable range (i.e., 9-40μm). Fibre wall thickness ranges from 3.31μm (for H. grandis) to 5.49μm (for Pterygota macrocarpa, Sterculiaceae) and is within pulpable range (2.90-5.15μm). Fibre walls for Meliaceae and Sterculiaceae are thick (> 4μm) but medium (2-4μm) for Ulmaceae. Runkel ratio of 2.65 (for C. odorata) to 3.9 (for C. milbraedii) is greater than stipulated for pulping (1.25). However, Flexibility Co-efficients (within 75-50 category) and fibre dimensions for timbers from the three families indicate their pulping suitability. It is anticipated the wood and construction industries exploit their fibre characteristics for structural applications and engineering of fibre-based products.