Mechanical properties of wood in an unstable state due to temperature changes, and analysis of the relevant mechanism, 5: Effects of thermal expansion and decomposition on destabilization of wood
2007
Wang, Y.(Kyoto Prefectural Univ. (Japan)) | Koma, S. | Iida, I.
In order to define the effects of thermal expansion and thermal decomposition on the destabilization of quenched wood, we measured the stress relaxation of steam-treated wood and oven-dried wood under control and quenching conditions, respectively. The degree of destabilization was evaluated by the fluidity (1-Esub(t)/Esub(0)) and its increase in relation to the control wood. The fluidity (1-Esub(t)/Esub(0)) of oven-dried wood clearly did not change after quenching. This meant that the reason for destabilization was not closely related with the thermal expansion of components. For steam-treated wood preheated below 120 deg C, the destabilization of the quenched sample was of the same degree as the control sample and was not related to the preheating time; however, when the preheating temperature was over 120 deg C, the degree of destabilization for the quenched sample was reduced with increasing preheating time. At the same time, for steam-treated wood preheated over 120 deg C, the change in lignin content was slight while the holocellulose content was greatly reduced, so it was inferred that destabilization had a close relationship with the holocellulose content. Moreover, it was indicated that changes in the hygroscopicity of wood due to holocellulose reduction affected destabilization.
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