Evaluation of capillary radii in wood by the centrifugal method.

1.用离心法估算了六种针叶树材的自由水路径尺寸分布。离心法是根据离心力降低的水势和弯月面的毛细压力与离心力的脱水自由水的量相平衡而发展起来的一种新方法。这种分布取决于树种和在木材中的位置。例如，早材的半径比晚材的半径大。这一结果被推测为未干燥木材的特征，而干燥后的木材则相反。2.用离心法定量地得到了局部蒸汽爆炸时自由水路的有效半径的变化。3.离心力对边材的凹坑破坏比心材更容易，因为凹坑边缘和环面之间的粘附力很强。杉木的圆环直径与坑孔直径之比大于杉木，且花旗松圆环的支撑力强于杉木。4.杉木边材的纹孔破损所需的作用力为0.1~0.2 Mpa。对于心材中的凹坑，离心法估计的值较大。这意味着木材中的凹坑有可能在干燥过程中被毛细管张力破坏。5.到目前为止，木材在潮湿条件下的接触角被认为是零。然而，这并不是事实。心材的润湿性比边材差，但经吸湿热处理后，两处的接触角相同。这一趋势与醇-苯萃取处理相同。这意味着细胞壁上浸出物的存在对润湿性甚至是湿状态都有影响。

1.The size distribution of free water paths for six species of softwood was estimated by centrifugal method which is a new method developed from the balance of water potential decreased by centrifugal force and capillary pressure by meniscus and the amount of dehydrated free water by centrifugal force. The distribution depends on species and the location in wood. For example, the radius in earlywood was larger than one in latewood. This result was presumed to be the feature for undried wood as there was the contrary result for dried sample.2.The change of effective radius of free water paths by local steam explosion was obtained quantitatively by the centrifugal method.3.The damage of pits by the centrifugal force was easier in sapwood than in heartwood because of the strength of adhesion between pit border and torus. Pits in Sugi damaged easier than those indouglas fir because the ratio of the diameters of torus and pit aperture is larger in douglas fir than in sugi and the torus in douglas fir was supported stronger than one in sugi.4.The force required for the damage of pits was 0.1 to 0.2 MPa for the sapwood in sugi. For the pits in heartwood larger value was estimated by centrifugal method. This means pits in wood has possibility to be damaged by capillary tension during drying.5.The contact angle of wood was considered to be zero in wet condition so far. However it was not truth. Wettability in heartwood was poor than sapwood, but after hygroscopic thermal treatment both location showed same contact angle. This tendency was same to the alcoholbenzene extractive treatment. This mean that the existence of the extracives on cell wall affects to the wettability even the wet condition.