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

超临界干燥长期保存浸水木材性能研究

基本信息

批准号：
07831010
负责人：
KAWAGOE Mikio
金额：
$ 1.66万
依托单位：
NARA NATIONAL COLLEGE OF TECHNOLOGY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

项目摘要

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.

环境湿度是影响长期保护中水口木材降解的最重要因素之一。湿度的变化不仅会影响诸如木材膨胀和/或收缩之类的物理特性，还会影响木纤维的化学变化，例如分解和降解。在本研究中，我们研究了湿度对景点传输现象的水槽木材的影响。Frist，我们测量了木材中的平衡水分含量，发现它们是湿度相对湿度的湿度小于80％的基础。接下来，测量了木质重量的响应曲线，以将湿度从30％变为80％。比较不同尺寸的木材的响应曲线，我们发现水分在木材中的扩散是速率控制步骤。然后，根据扩散模型估算差异。结果，我们发现了木材的扩散系数，d_a和明显的密度之间的以下相关性，rho_b：d_arho_b g/（cm・天），d_a和rho_b分别在cm^2/day和g/cm^3中。比较我们先前获得天然干燥的相似相关性，本研究中获得的扩散系数大约是天然干燥的扩散系数的大约3.5倍，因为超临界干燥没有发生极端的木材收缩，：木材在自然干燥的降低率中收缩了极高的收缩。此外，我们测量了用聚乙烯乙二醇（PEG）浸渍的木材的扩散系数。从上述相关性估计的木材浸入木材的扩散系数约为十分之一。因此，我们发现（用于超临界干燥木材的D_A）>（天然干燥木材的D_A）>（D_A浸入钉子的木材）。这一事实意味着，木材重量对湿度的变化的反应是上面三者中最快的。