汽蒸处理对落叶松木材物理性质的影响

本文取兴安落叶松(Larix gmelinii Rupr)生材加工成规格为20mm×20mm×20mm的试样;于常压下汽蒸1、2、4、8、16、32、48、64、96h。测定了气干和全干状态的干缩率、气干密度、基本密度和平衡含水率(EMC)等物理性质的变化情况。结果表明:①木材全干干缩率除汽蒸初始1h略有下降外,均随汽蒸的延续而逐渐增加,至64 h达最大值,径向、弦向和体积干缩率分别为7.28％、13.40％和21.85％,若继续延长汽蒸时间,干缩率稍有降低。②汽蒸过程中差异干缩值的变化不大,稍有降低。因而,汽蒸不会加剧差异干缩,并能使其有所改善。③气干密度和基本密度均随汽蒸的延续而逐渐降低,至48h降达最低值,分别为0.615g/cm~3和0.487g/cm~3,若继续汽蒸,气干密度和基本密度均稍有回升。④平衡含水率(EMC)随汽蒸的延续而逐渐降低,汽蒸96h降为8.53％。因此,汽蒸处理对落叶松木材物理性质的影响不大,落叶松成材汽蒸处理时间,一般不宜超过16h。

INFLUENCE OF STEAMING ON PROPERTIES OF WOOD

Larch cubes of 20 mm were exposed to steaming at normal atmosphere for periods of 1, 2, 4, 8, 16, 32, 48, 64, and 96 hours. Tangential, radial, and volumeric shrinkage, density, specific gravity and equilibrium moisture content (EMC)were determined, the results of the test are given as follows: 1. For the beginning one hour of steaming, shrinkage reduces slightly, then increased, and steaming for 64 hours the shrinkage arrived the maximum value. Tangential, radial, and volumeric shrinkage is 72.8%, 13.4% and 21.85%, respectively. The shrinkage lowed slightly, if the time increased. 2. Change in anisotropic shrinkage is not great, during steaming process, steaming can not intensify the shrinkage, and can improve it. 3. The airdry density and specific gravity reduced with time increased, up to 48 hours, the value of air-dry density and specific gravity arrived the minimum of 0.615g/cra and 0.487g/cm~3. Then has gone up. 4. The equilibrium moisture content reduced with the steaming time, reduced by 8.53% for 96 hours of steaming. Therefore, the effect of steaming on larch physical property is not great, larch wood should not be exposed to steaming for more than 16 hours.