<論文>マイクロ波加熱による木材の曲げ加工 : 横方向曲げ処理材の水分・熱回復

Abstract

マイクロ波加熱を利用して木材の横方向の曲げ加工を試み,組織構造上に現われる変化をSEMを用いて観察した。また曲げ加工材の変形の水分および熱による目視を調べた。細胞は,引張側では引張応力の作用した方向に伸び,逆にヂ縮側では圧縮応力の作用した方向に縮んだ様子が明確に観察された。庄縮側の細胞の半径壁では,壁表面の凹凸および壁孔口の変形が顕著に認められた。曲げ加工科の変形ぱ水分と熱によってほぼ完全に回復した。針葉樹科と広葉樹科の間に,回復の様子に差異が認められ,その原因は木材成分割合の達しに基づくものと思われた。また,水分と熱によって変形の回復した科では,細胞および細胞壁に見られた変形は,ほとんど消失した。

Wood pieces were bent in the direction perpendicular to grain during microwave irradiation and changes occurred in the anatomical structure of the bent pieces were examined through SEM observation. Furthermore, changes in curvature of the bent piece by moisture and heat treatments were investigated. Cells on the convex and concave sides of the bent piece were extremely extended and contracted to the directions of induced tensile and compressive stresses, respectively. Irregularities of the wall surface and distorted pit apertures were found on the radial walls on the concave side. The bent pieces returned almost to their original shapes when they were subjected to moisure and heat treatments. However, the extent of the recoveries by the respective treatments was different between hardwoods and softwoods. One of the causes seemed to be resulted from the different proportions in the chemical constituents. By such treatments the irregularities of the wall surface were disappered and the distorted cells returned to their original shapes.