Solvent exchange for wood .1. Dimensional change of wood during and after solvent exchange

The dimensional changes of wood during and after solvent exchange for several systems were studied as the first step for clarifying the mechanism of the shrinkage of wood during solvent exchange. The shrinkage in the course of replacement from polar intermediate solvents to non-polar final solvent was varied largely with the sets of intermediate and final solvents (Fig. 1). The shrinkage in the systems in which n-hexane was used as a final solvent was much lager than that in which benzene having a certain extent of proton accepting property was used (Fig. 1). This probably means that the adsorptivity of the final solvents to the sites on the surfaces of fine voids in the cell walls of wood strongly affects the shrinkage of wood during solvent exchange. The study showed that the desorption of the final solvents from the adsorption sites in the cell walls is one reason for the shrinkage of wood during and after solvent exchange, although, in the previous studies,(1-3,13)) the shrinkage was thought to result only from the incomplete replacement of final to intermediate solvents, which occus when intermediate solvents is removed without having been replaced. In the next step of this series for clarifying the mechanism of the shrinkage of wood during solvent exchange, adsorptivities of both replacing and replaced solvents, leached volumes of replaced solvents from cell walls and the residual amounts in cell walls should be studied in relation to the dimensional changes.