水分の脱着による木材の赤外線吸収スペクトルの変化

Abstract

水分の脱着によって起る木材の微細構造的な変化を明らかにするため赤外分光法の適用を試みた。木材中の水分の脱着により, その赤外線吸収スペクトルの吸収帯に変化が認められたのは3350, 1635, 1450, 1340, 1110, 1060および1040cm_-1である。これら吸収帯のうち3350と1635cm_‐1は吸着した水分子自体の脱着にもとずくものであり, 他の吸収帯は脱着による木材の微細構造の変化に対応するものと推定される。比較的変化量の大きい吸収帯1110, 1060および1040cm_-1について水分の脱着様式を変えることによっでそれぞれの吸収帯の変化を検討した結果, これらの一連の吸収帯が水分の脱着によってもたらされる木材の微細構造の変化に対応することがわかった。

The changes of the fine structure in wood caused by desorption of water was prelimarily investigated by means of infrared spectroscopy. The infrared spectra of wood both in wet and dry state are shown in Fig. 2. The intensities of infrared absorption bands at 3350, 1635, 1450, 1340, 1110, 1060 and 1040cm.-1 changed as desorption of water from wood proceeded. The intensity decrease in the bands at 3350 and 1635cm.-1 is directly related to the desorption of H2O molecules from wood. On the other hand, the intensity increase in the bands at 1450, 1340, 1110, 1060 and 1040cm.-1 might be caused by the changes of the fine structure in wood on desorption. The bands at 1110, 1060 and 1040cm.-1, whose intensities increase pronouncedly during the desorption process, have been studied in detail. The effect of water desorption on fine structure of wood was studied by the following procedures examining the infrared spectrogram in 1200 ~ 900cm.-1 region; i.e., 1) changing the relative humidity, 2) drying the wetted samples at -80℃ and 20℃ in vacuo, 3) heat-drying of the wetted sample with and without tension during drying. In the process of the results obtained are shown in Figs. 3, 4 and 5. On the basis of these data, it seems to be reasonable to assume that the intensity increase of these three bands (1110, 1060 and 1040cm.-1) on desorption represents the molecular structure change of wood, that is, the degree of orientation in the amorphous region is increased by reorientating the molecular chains in wood during desorption.