Solvent extraction of inhibitory substances from three hardwoods of different densities and their compatibility with cement in composite production

Abstract

Chemical pre-treatment of wood to remove extractives improves timber’s compatibility with cement and produces strong composites. The chemicals often used are expensive and environmentally-destructive. Data on eco-friendly solvents for such extraction are deficient, which makes it difficult to recommend the most effective solvent for wood pre-treatment. This study compared the extracting potentials of three readily available and environmentally friendly solvents (i.e. ethanol, hot and cold water) and their influence on the thickness swelling, modulus of rupture and shear strength of composites produced from three hardwoods of different densities [Klainedoxa gabonensis (high), Entandrophragma cylindricum (medium) and Triplochiton scleroxylon (low)]. Hot water removed more extractives (e.g. 2.21 ± 0.07% from T. scleroxylon) than ethanol (0.925 ± 0.02% from T. scleroxylon) and cold water (0.865 ± 0.02% from T. scleroxylon). Composites from hot water-extracted sawdust least swelled and were stronger than those produced from the ethanol-, cold water- and non-extracted sawdust. T. scleroxylon boards from both extracted and non-extracted sawdust had the lowest thickness swelling and greatest strength. Hot water was found to be more effective than cold water and ethanol for pre-treating the sawdust, especially those from the light timbers (e.g. T. scleroxylon) before mixing with cement in producing strong and dimensionally stable composites. Utilization of sawdust, especially from these timbers, would contribute to increasing the raw material base for the wood–cement board manufacturing or the composite industry.