Determining the Effect of Extractives on Moisture Movement Using a "Continuous" Measuring System

Yong Chen, Elvin T. Choong


Red oak (Quercus sp.) heartwood samples were treated by (1) steaming at atmospheric pressure for 6 h; (2) hot-water soaking at 70 C for 24 h; and (3) ethyl alcohol extraction in a Soxhlet extractor for 24 h after hot-water soaking. All samples were soaked in water and treated by vacuum-atmosphere method. Each sample was then coated with waterproof resin to ensure unidirectional radial movement of moisture. An environmental box equipped with an electric fan was designed and built for the purpose of achieving "continuous" measuring. Potassium chloride salt was used to control the relative humidity to 82% at 40 C. The sample was hung on a digital balance, which was connected to a printer, and the weight loss was recorded in 5-min intervals by a computer-controlled data acquisition system. Experimental results indicated that all treated samples, as compared with the untreated samples, increased the diffusion coefficients and therefore the drying rate significantly. The differences among treatments were not statistically significant. The major effect of the extractives came from the water-soluble components. The removal of extractives increased the drying rate in the falling rate period.


Extractives;red oak;diffusion;moisture movement;falling rate period;drying rate;steaming;hot-water soaking

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