Study on Properties of Waterlogged Woods Treated by Supercritical Drying in a Long-Term Conservation

环境人性是一个最重要的因素，它会影响到长期保护中水分森林的退化。人类效应的变化不仅限于物理性质的变化，如森林的扩展和/或收缩，但也包括木材纤维的化学变化如分解和退化。在目前的研究中，我们调查了从观察点传输现象的木材中湿度对湿度的影响。弗里斯特，我们测量了森林中的equilibrium moisture content，并发现了他们可能对湿度低于80%的相对湿度的相对湿度。下一个，reverse curves of the wood weight were measured for step change of the humidity from 30% to 80%。用不同大小的木材比较响应曲线，我们在木材中发现了水分的差异就是控制速率的步骤。然后，扩散系数是根据扩散模型估计的。作为一个结果，我们找到了扩散系数、D_A和木材的明显密度，rho_B：D_Arho_B g/（cm·Day）在哪里，D_A和rho_B在cm^2/Day和g/cm^3，相应地。比较我们以前发现的类似的相关性，目前在自然干燥中发现的扩散协同效应约为3.5次，就像那些人对自然干燥的人一样大，因为没有对超临界干燥的木材的极端接触， ：森林在自然干燥期间对自然干燥产生了极大的影响。更进一步，我们测量了一种被聚乙烯醇（PEG）污染的木质混合物。与PEG一起被木质植入的差异性相关的物质大约有10个，其中一个估计来自以上相关性。顺便说一下，我们找到了（D_A用于超临界干燥木材）>（D_A用于天然干燥木材）>（D_A用于PEG中的木材）。这一事实表明，木材重量对人类变化的反应是三个人之间最快的。

Ambient humidity is one the most important factor which affects the degradation of waterlogged woods in a long-term conservation. Change of the humidity affects not only on physical properties such as expansion and/or contraction of woods but also on chemical change of wood fiber such as decomposition and degradation. In the present study, we investigated the effects of humidity on the waterlogged wood from the view point transport phenomena.Frist, we measured equilibrium moisture contents in the woods, and found that they are propportional to the relative humidity for the humidity less than 80%. Next, reponse curves of the wood weight were measured for step change of the humidity from 30% to 80%. Comparing the response curves for woods with different size, we found diffusion of moisture in the wood is the rate controling step. Then, diffusion coefficients were estimated based on the diffusion model. As a result, we found the following correlation between the diffusion coefficient, D_A, and apparent density of wood, rho_B :D_Arho_B g/(cm・day)where, D_A and rho_B are in cm^2/day and g/cm^3, respectively. Comparing the similar correlation we obtained previously for natural drying, the diffusion coefficients obtained in the present study were about 3.5 times as large as the ones for natural drying, because no extreme contraction of wood occured for the supercritical drying, : woods contracted extremely in the falling-rate period for the natural drying. Further, we measured the diffusion coefficient for a wood impregnated with polyethylene glycol (PEG). The diffusion coefficient for wood impregnated with PEG was about one tenth the one estimated from the above correlation. Consequently, we found that (D_A for supercritical drying wood)>(D_A for natural drying wood)>(D_A for wood impregnated with PEG). This fact implies that the reponse of wood weight against the change of humidity is the fastest among three of them above.