热处理对桉材皱缩的作用

EFFECT ON COLLAPSE OF EUCALYPTUS WOOD BY HEAT TREATMENT

多枝桉、细叶桉、赤桉采用恒温调温干燥法测绘含水率－收缩曲线，探求热处理对改善桉材皱缩的效果。结果多枝桉、细叶桉是否热处理均具典型的“皱缩”型含水率－收缩曲线，但热处理材少有“二段”皱缩，“肩点”处收缩率和全收缩率比未热处理材小，处理效果明显；赤桉则无区别。同时，论述了“皱缩”型曲线出现“肩点”的必然性；提出了“二阶段”皱缩理论；并对寺［１］等的“导管二次皱缩”论的局限性进行了探讨．

In order to understand the effect of heat treatment upon the collapse. of Eucalyptus wood,moisture content- shrinkage curves are measured and drawn in this paper by means of drying at constant temperature and various humidity for treated and untreated Eucalyptus viminalis、E. tereticornis and E.camaldulensis. The result shows that whether heat treated or not,E. viminalis and E.tereticornis have the typical'collapse pattern'moisture content -shrinkage curve.For heat treated timber of the two species,however,the second stage collapse appears rarely and the whole shrinkage and shrinkage at'shoulder point'are lower than that of untreated timber. Effect of heat treatment is apparent on E.viminalis and E. tereticornis.no effect on E.camaldulensis, This paper has introduced a two stage collapse theory and expounded for the first time that it is inevitable to appear'shoulder point'in the 'collapse pattern' moisture content -shrinkage curve,and illustrated the limitation of the'indirect vessel collapse'theory presented by Shin Terazawa