DETERMINING THE EFFECT OF EXTRACTIVES ON MOISTURE MOVEMENT USING A CONTINUOUS MEASURING SYSTEM

Red oak (Quercus sp.) heartwood samples were treated by (1) steaming a t 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 aft er 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 environ mental box equipped with an electric fan was designed and built for th e purpose of achieving ''continuous'' measuring. Potassium chloride sa lt was used to control the relative humidity to 82% at 40 C. The sampl e 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-control led data acquisition system. Experimental results indicated that all t reated samples, as compared with the untreated samples, increased the diffusion coefficients and therefore the drying rate significantly. Th e differences among treatments were not statistically significant. The major effect of the extractives came from the water-soluble component s. The removal of extractives increased the drying rate in the falling rate period.