Influence of heating history on dynamic viscoelastic properties and dimensions of dry wood |
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Authors: | Keisuke Kojiro Yuzo Furuta Yutaka Ishimaru |
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Institution: | (1) Biological Function Science Course, Research Division of Agriculture, Graduate School of Kyoto Prefectural University, 1-5 Shimogamo Hangi-cho, Sakyo-ku, Kyoto 606-8522, Japan |
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Abstract: | To obtain new information about the mechanical and physical properties of dry wood in unstable states, the influence of heating
history on viscoelastic properties and dimensional changes of dry wood in the radial, tangential, and longitudinal directions
was studied between 100° and 200°C. Unstable states of dry wood still existed after heating at 105°C for 30 min and were modified
by activated molecular motion in the first heating process to temperatures above 105°C. This phenomenon is thought to be caused
by the unstable states reappearing after wetting and drying again. Dry wood components did not completely approach the stable
state in the temperature range tested, because they did not entirely surpass the glass transition temperatures in most of
the temperature range. In constant temperature processes at 135° and 165°C, E′ increased and E″ decreased with time regardless of the direction. This indicated that the unstable states of dry wood components were gradually
modified with time at constant temperatures. On the other hand, anisotropy of dimensional change existed and dimension increased
in the longitudinal direction, was unchanged in the radial direction, and decreased in the tangential direction with time
at constant temperatures.
Part of this report was presented at the 13th Annual Meeting of the Chubu Branch of the Japan Wood Research Society, Shizuoka,
August 2003 |
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Keywords: | Dry wood Unstable state Dynamic viscoelastic property Dimensional change Heating |
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