文献类型：期刊文献

中文题名：基于动态热机械分析仪的木材干缩湿胀响应特征研究

英文题名：Investigation of wood swelling and shrinkage by means of dynamic mechanical analyzer

作者：彭辉[1] 蒋佳荔[2] 詹天翼[1] 吕建雄[1,2]

第一作者：彭辉

机构：[1]南京林业大学材料科学与工程学院,南京210037;[2]中国林业科学研究院木材工业研究所,国家林业和草原局木材科学与技术重点实验室,北京100091

年份：2023

卷号：8

期号：2

起止页码：52-58

中文期刊名：林业工程学报

外文期刊名：Journal of Forestry Engineering

收录：CSTPCD;;北大核心:【北大核心2020】；CSCD:【CSCD_E2023_2024】；

基金：国家自然科学基金(32101454)。

语种：中文

中文关键词：动态热机械分析仪;干缩湿胀;吸着;解吸

外文关键词：dynamic mechanical analyzer;swelling and shrinkage;adsorption;desorption

分类号：S781

摘要：探究了动态热机械分析仪(DMA)测试自由缩胀应变的可行性,揭示了影响木材干缩湿胀应变的主要因子。对比干燥器调湿法和DMA测试法获得的一系列平衡含水率下的全干材(0.6%含水率)湿胀应变量,验证DMA测试干缩湿胀的可行性,从而进一步利用DMA分别测试全干材吸湿、湿材解吸和全干材吸湿-解吸循环过程的干缩湿胀形变。结果表明:干燥器调湿法和DMA测试法测得的应变量数据非常相近,但由于干燥器调湿法人工测量过程中存在误差,使得其数据变异性高于DMA测试法。同一含水率下,水分平衡态和非平衡态下的干缩或湿胀应变量近乎相等。对于水分非平衡态(吸着/解吸过程),不同相对湿度水平下的湿胀/干缩应变量-含水率曲线几乎重合。在水分吸着-解吸循环过程中,湿胀-干缩应变量交替出现的峰值和谷值时间节点滞后于湿度变化,随着循环次数的增加,滞后时间有所缩短。因此,DMA作为干缩湿胀应变量测试的方法是可行的,可以实现水分变化过程中干缩湿胀应变量的实时、快速和准确测量。干缩或湿胀应变量与水分平衡态和非平衡态无关。不同湿度水平下,含水率与干缩/湿胀应变量曲线重合,表明干缩/湿胀变形主要受含水率影响,与湿度水平无关;但相比吸着过程,解吸过程较低的应变量揭示了木材干缩湿胀与水分子吸着状态有关。
The swelling and shrinkage of wood are closely associated with moisture content. The effect of equilibrium moisture content on swelling and shrinkage has been well explored, while the data at un-equilibrium state is still unclear and more valuable for applications of wood products. In order to investigate the swelling-shrinkage response to moisture, it is necessary to find a fast and accurate testing method. Herein, the application of dynamic mechanical analyzer(DMA) on swelling-shrinkage test was explored, and the determination factors for swelling-shrinkage were revealed as well. To confirm the feasibility of DMA, the dried sample with 0.6% moisture content was used to measure swelling at a series of equilibrium moisture content by means of sealed container and DMA respectively. Then the swelling-shrinkage examination was conducted by DMA during adsorption, desorption, and cyclic adsorption/deso-rption processes. The results showed that there was small difference between the data obtained by the sealed container and DMA, although the data from sealed container was more scattered due to the manual measurement errors. For a given moisture content, the strain at equilibrium state was almost equal with that at the un-equilibrium state, indicating no moisture gradient in wood samples. During both adsorption and desorption processes, the plots “swelling/shrinkage strain vs. moisture content” from different relative humidity levels were almost overlapped, revealing that the moisture content was the key factor for swelling-shrinkage. The change of strain per moisture content was lower than 5% moi-sture content, attributing to the existent of monolayer absorbed water. During the cyclic process, the swelling-shrinkage was lagged the imposed relative humidity, and the lagged time decreased with increasing cyclic periods. There was sorption hysteresis in the first cyclic process, because the inelasticity strain occurred during the adsorption and the relaxation of the matrix during desorption to the state, which was kinetically hindered during adsorption. As a consequence, DMA was a useful method to measure swelling/shrinkage quickly and accurately. The swelling/shrinkage was independent of equilibrium or un-equilibrium state, and closely related to moisture content rather than relative humidity. Moreover, the lower strain during desorption indicated that the moisture molecular state had an effect on hygro-expansion behavior.