Evaluation of capillary radii in wood by the centrifugal method.

1.利用离心法估算了6种针叶材自由水路径的尺寸分布，该方法是根据离心力降低的水势与弯月面毛细压力的平衡关系以及离心力脱水后的自由水的量而发展起来的一种新方法。分布取决于树种和在木材中的位置。例如，早材的半径大于晚材。2.采用离心法定量测定了局部蒸汽爆破后自由水路径有效半径的变化; 3.由于纹孔边缘与纹孔环之间的粘附力较强，边材比心材更容易受到离心力的破坏。杉材的纹孔破坏比杉木容易，这是因为杉木的纹孔直径与纹孔孔径的比值比杉材大，杉木的纹孔受到的支撑比杉材强。4.杉材边材纹孔破坏所需的力为0.1 ~ 0.2MPa。对于心材中的纹孔，用离心法估算的值较大。这意味着在干燥过程中，木材中的凹坑有可能被毛细张力破坏。5.目前，木材在潮湿条件下的接触角被认为是零。但这不是事实。心材的润湿性比边材差，但经吸湿热处理后，两者的接触角基本相同。这一趋势与苯醇抽提处理相同。这说明细胞壁上的胞外物质的存在对润湿性有影响，甚至在润湿状态下也有影响。

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.