Heating Dry Wood and Drying Green Wood in Molten Polyethylene Glycol

Thin, dry cross-sections of Douglas-fir were subjected to a combined heat stabilization and polyethylene glycol-1000 bulking action by heating them beneath the surface of the molten polyethylene glycol at 180?C for various periods of time. Although the take up of polyethylene glycol was large, practically no swelling occurred until the specimens were wet with water. Subsequent drying resulted in good bulking and reductions in shrinkage. When the polyethylene glycol was leached from the wood, the subsequent reduction in shrinkage was reduced to that obtained by heating dry untreated wood beneath the surface of a molten metal, showing that the polyethylene glycol has no specific heat stabilizing effect. The bulking by the polyethylene glycol for the combined treatments was shown, however, to be inhibited by the heat stabilization. The roughness and abrasion resistance of loblolly pine specimens, which were previously subjected to the combined heat and polyethylene glycol treatments, was considerably better than for heat stabilization alone in molten metal. The values for the combined treatment were, however, no better than for polyethylene glycol treatment alone. In drying 5- by 3- by 3/8-inch quarter sawn loblolly pine from a moisture content of 91 percent while immersed in polyethylene glycol at 135? and 180?C the specimens lost weight faster than in drying in air at the same temperatures. This was shown to be largely due to better heat transfer to the wood by the liquid polyethylene glycol. No darkening of the wood and degrade occurred. Measurements on more refractory woods will have to be made before the desirability of drying wood in such a hygroscopic liquid medium can be determined.

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