REDISTRIBUTION OF SOLVENT AND SOLUTE DURING DRYING OF RUBBERWOOD IMPREGNATED WITH NON-AQUEOUS OR AQUEOUS LIQUIDS

Abstract

MUHAMMED S, MUSGRAVE OC & PETTY JA. 2011. Redistribution of solvent and solute during drying of rubberwood impregnated with non-aqueous or aqueous liquids. End-sealed rubberwood blocks were impregnated with a 1:l v/v mixture of 1-bromopropane and cyclohexane via their radial and tangential surfaces and allowed to dry slowly at 20 °C. X-radiography through the transverse surface showed that the concentrations of 1-bromopropane were consistently higher in the centre than in the periphery of the block. A similar impregnation using cyclohexane alone resulted in the concentration at the centre of the block being initially somewhat lower than that at the periphery. However, after part of the solvent had evaporated, the concentration at the centre was relatively much higher. Two rubberwood blocks were impregnated via their radial and tangential, and transverse surfaces with a solution of copper naphthenate in cyclohexane. The blocks were then covered so that evaporation of the solvent from one block took place only via the radial and tangential surfaces and from the other only via the transverse surfaces. Radiography of the former showed that copper concentration was high at the periphery and low at the centre of the block. Radiography of the latter block showed uniform copper distribution across the transverse section. The substitution of an aqueous solution of copper sulphate resulted in a similar behaviour. These observations support the view that rubberwood offers little resistance to impregnation by liquids. Drying of the treated wood is accompanied by considerable movement of the liquid to the periphery where evaporation takes place. Any involatile solute present is deposited at or near the surface.