不同溫度熱處理柳杉與相思樹木材之特性

Abstract

In this study, a non-toxic heat-treated technology was applied for improving the dimensional stability of wood. A 20-30 years old Cryptomeria japonica and Acacia confusa wood with thickness of 5 cm and moisture content of 12% were used. The heat treatment was conducted using an activated furnace under N2 atmosphere and the samples were subjected to heat treatment at 130, 160, 190, 220, 250, and 280℃, respectively at a heating rate of 20℃/hr and holding time of 2 hr. The characteristics of heat-treated wood such as mass loss, moisture content, density, shrinkage ratio, color change, roughness, dimensional stability contact angle, surface hardness, static bending strength as well as Fourier transform infrared spectroscopy (FT-IR) analysis were examined. The results showed that the mass loss and color difference (△E*) of heated-treated wood increased with increasing heated temperatures, while the moisture content and density had the reverse results. Furthermore, after heated treatment the smoother surface of wood was obtained. The anti-swelling efficiency (ASE) and moisture excluding efficiency (MEE) could be improved significantly at higher heat-treated temperatures. The surface hardness of below 220℃ heat-treated C. japonica wood was higher than that of un-treated wood. The surface hardness of below 190℃ heat-treated A. confusa wood was higher than that of un-treated wood, while the hardness decreased significantly for the one over 190℃ treatment. The modulus of rupture (MOR) of wood with over 190℃ treatment decreased with increasing heated temperatures. However, C. japonica and A. confusa with 160 and 190℃ treatment had the highest modulus of elasticity (MOE). According to FT-IR, the contents of hemicellulose and cellulose of treated wood were lower than those of untreated wood, and which decreased with increasing heated temperatures. But the relative content of lignin increased with increasing heated temperatures.本研究係以無毒之熱處理技術，擬改善木材尺寸安定性。材料為20-30年生，厚度5 cm之柳杉（Cryptomeria japonica）與相思樹（Acacia confusa），含水率12%；利用炭化爐，通入N2，在升溫速率20℃/ hr下，分別加熱至130、160、190、220、250及280℃，並持溫2 hr進行熱處理，探討不同溫度熱處理材之質量損失、密度、平衡含水率、尺寸減低率、色差值、粗糙度、尺寸安定性、接觸角、硬度、抗彎強度及傅立葉紅外線光譜（FT-IR）分析。試驗結果顯示，柳杉與相思樹木材經不同溫度熱處理後，質量損失隨處理溫度提高而增加，而密度與平衡含水率明顯降低；色差值（△E*）隨熱處理溫度之提升而增加，表面粗糙度經熱處理後則較為平滑；抗膨脹效能（Anti-swelling effi ciency,ASE）與抗吸濕效能（Moisture excluding efficiency, MEE）隨熱處理溫度提高有明顯之改善效果。柳杉與相思樹材經熱處理後，木材表面具較佳疏水性，且會隨熱處理溫度升高而增加。在熱處理材之表面硬度方面，柳杉木材以220℃以下處理之硬度值較未處理材高，且會隨溫度升高而增加，而相思樹木材以190℃以下處理之硬度值較未處理材為高，但以190℃以上熱處理硬度則明顯降低。兩種木材之抗彎強度（Modulus of rupture, MOR）均隨隨熱處理溫度增加而降低，但柳杉與相思樹之抗彎彈性模數 （Modulus of elasticity, MOE）分別以溫度160與190℃熱處理者最佳。在傅立葉紅外線光譜（Fourier transform infrared spectroscopy, FT-IR）分析顯示，經熱處理後木材半纖維素及纖維素含量明顯減少，且隨處理溫度增加而降低更多，但木質素相對含量則隨處理溫度增加而提高