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热处理对木材吸湿特性及尺寸稳定性的影响

DOI: 10.3969/j.issn.1000-2006.2015.02.025

Keywords: 木材热处理, 蒸汽压力, 吸湿性, 尺寸稳定性
wood heat treatment
, steam pressure, moisture sorption, dimensional stability

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Abstract:

分别在常压蒸汽与0.45 MPa加压蒸汽条件下,对樟子松和柞木进行热处理,比较了热处理材和未处理材的水分吸湿性及尺寸稳定性差异。结果表明:两种试材经过热处理后不仅吸湿量明显降低,在高湿条件下的吸湿特性也发生了显著变化,当环境相对湿度从69%增至94%时,热处理材的平衡含水率变化率仅为对照材的1/3,细胞壁微观构造在高温条件下的变化可能是造成这一现象的主要原因; 吸湿性的降低使热处理材的尺寸稳定性获得了大幅度提高,樟子松试材加压蒸汽热处理后径、弦向湿胀率分别下降了34%和47%,柞木则分别降低了46%和51%; 热处理材的弦向抗湿涨系数普遍高于径向抗湿涨系数,表明木材径、弦向的湿胀差异在热处理后也有所缩减; 加压蒸汽热处理比常压蒸汽热处理的改性效果更为显著。
Heat treatment of Pinus sylvestris and Quercus mongolica boards were carried out in atmospheric stream or 0.45 MPa pressurized steam. Hygroscopicity and dimensional stability of the treated wood were compared with the control. The results showed that heat treatments not only lowered the equilibrium moisture contents(EMC)of the wood, but also altered the pattern of its moisture adsorption in high humidity environment. When the environmental relative humidity increased from 69% to 94%, the EMC change rates of the heat treated samples were just one third of those of the control samples. This might be attributed to the reconstruction of wood cell wall during the heat treatments. Dimensional stability of heat treated samples was significantly improved as a result. The radial and tangential swelling of pressurized-steam treated Pinus sylvestris samples decreased by 34% and 47% compared to those of the control ones. For Quercus mongolica samples, the corresponding values were 46% and 51%. Most tangential anti-swelling efficiency(ASE)values of the heat treated samples were higher than their radial ASE values. That means swelling difference between radial direction and tangential direction was also reduced after heat treatments. It was also showed that pressurized steam induces more pronounced property modification than atmospheric steam

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