EFFECT OF SELECTED WATER-SOLUBLE BULKING CHEMICALS ON MOISTURE DIFFUSION AND DIMENSIONAL STABILITY OF WOOD

This paper investigated the water-soluble bulking chemicals in wood that affect the movement of moisture during drying. The optimization method was applied to calculate the average diffusion coefficients. Hot-water soaking to remove most of the water-soluble extractives slightly increased the diffusion coefficients and decreased the dimensional stability of redwood heartwood, but did not significantly increase the diffusion coefficients of red oak heartwood. Impregnating southern pine and yellow-poplar sapwood with polyethylene glycol or condensed tannin considerably decreased diffusion coefficients and increased dimensional stability. Shrinkage data and the amount of bulking chemicals in wood supported the hypothesis that the changes in drying rate and dimensional stability are due to blockage of the macro-passageways in the cell void spaces and the bulking effect of the cell wall. The possible mechanisms of bulking chemicals affecting moisture diffusion in wood are discussed.