摘要
采用高温干燥、低温干燥和真空冷冻干燥方法对杉木人工林木材进行干燥处理,测定3种干燥处理材在不同含水率平衡态的动态黏弹性质。测定的温度范围为-120～40℃,频率范围为0.5～10 Hz。结果表明：1）随着含水率增加,木材的贮存模量E′随温度升高而降低的程度增大,其中高温干燥处理材的贮存模量降低程度最小;2）在测定温度范围内观察到2个力学松弛过程,较高温度域的α力学松弛过程是由低分子质量的半纤维素发生玻璃化转变引起的,低温域的β力学松弛过程是基于木材细胞壁无定型区中伯醇羟基的回转取向运动与吸着水分子的回转取向运动两者叠加而成的;3）力学松弛过程的损耗峰温度随着含水率的增加而降低,随着测量频率的增加而向高温方向移动;4）力学松弛过程的表观活化能随着含水率的增加而减小,对于α力学松弛过程,高温和低温干燥处理材的表观活化能低于真空冷冻干燥处理材的表观活化能。
In this study, Chinese Fir （Cunninghamia lanceolata ） plantation wood was dried by high-temperature drying （HTD）, low-temperature drying（LTD） and freeze-vacuum drying （FVD） methods, and their dynamic viscoelastic properties were tested at various humidity environments. The measurements were done in the temperature range of- 120 to 40 % at frequencies ranging between 0.5 to 10 Hz. The results showed that： with the increase of moisture contents, the decrease of storage modulus with increasing temperature became more dramatically. The decrease extent of storage modulus was the lowest for high-temperature dried wood. Two mechanical relaxation processes were observed for three kinds of dried woods. The a relaxation process in higher temperature range was due to glass transition of hemicellulose with low molecular weight, while the t3 relaxation process occurred in lower temperature range was based on the reorientation of methylol groups in amorphous of wood cell wall and the reorientation of adsorbed water molecule in wood. The loss peak temperature of mechanical relaxation processes moved to lower temperature range with the increase of moisture contents, and moved to higher temperature range with the testing frequency increase. The apparent activation energy of mechanical relaxation processes decreased with the increase of moisture contents. For relaxation process, high-temperature and low-temperature dried woods showed lower value than that for freeze-vacuum dried wood.
出处
《林业科学》
EI
CAS
CSCD
北大核心
2008年第9期118-124,共7页
Scientia Silvae Sinicae
基金
国家自然科学基金项目(30671635)
关键词
干燥处理材
力学松弛过程
含水率
表观活化能
dried wood
mechanical relaxation process
moisture content
apparent activation energy
