空気存在下における熱処理針葉樹材の微細構造の研究

Abstract

加熱処理 (300℃) による木材の微細構造の変化を示差熱分析法, 熱重量分析法, X線回折法および赤外線分光法により検討した。木材が加熱された場合, 110℃付近で水分の脱着により生ずる分子の再配列の結果もたらされた結晶性の増加をX線的に認めた。また210℃付近から結晶構造の崩壊が始まり, 270℃付近で終局に至り, その温度付近より分子構造の分解反応が促進され, 重量減少, 一部揮発物の燃焼, 分解生成物の再結合, 環化などの反応が同時におこっていることが推定された。

This work was undertaken to examine the effects of heat-treatment under the temperature range of 90℃ to 300℃ upon the fine structure of wood. The specimens used in this study were taken from Japanese red pine (Pinus densiflora Sieb. et Zucc.) wood. The experiment was carried out as follows; the thermal reaction was examined by differential thermal analysis (D. T. A.), the weight loss on heating wood by thermogravimentric analysis (T. G. A.), the decomposition of the crystalline region of wood by heat-treatment by X-ray diffraction analysis, and the change of chemical composition of heated wood by infrared spectroscopic analysis, respectively. As a result, it is shown by D.T.A. (Fig. 1) that there are mainly three thermal reaction stages; the initial peaks near 110℃ are due to dehydration of absorbed water, the peaks near 300℃ are attributed to flaming of volatile products of the initial pyrolysis, and the sharp peaks near 370℃ are due to glowing combution of the residual char. And it is observed from T.G.A. (Fig. 2) that the weight loss of wood by heat-treatment progresses slowly from 50℃ to 110℃ and then reaches the maximum near 300℃ and to its final stage beyond 300℃. In addition, it is comfirmed from X-ray diffraction analysis (Fig. 3, 4 and 5) that the crystalline structure of wood does not change by the heat-treatment under the temperature bellow about 210℃, and beyond 210℃ it gradually begins to decompose as the temperature increases, and then it finally reaches to the amorphous state near 270℃ (see Fig. 3 and 5), that the peak intensity of (002) plane decreases linearly beyond 230℃ with the heating time (see Fig. 4) and that the increase of the peak intensity of (002) plane by heat-treatment at 110℃ for 5 hours may be associated with the orientation of molecular chains in the para-crystalline region (see Fig. 3). It is found from infrared analysis (Fig. 6) that the absorption bands at 1720cm-1, 1600cm-1 and 760cm-1 appear or increase their intensity as the temperature increases beyond 210℃.