Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/95730
標題: 不同金屬烷氧化合物處理對木材–無機複合材物理機械、熱分解以及潛變性質之影響
Effect of different metal alkoxide treatments on physicomechanical, thermal decomposition, and creep properties of wood-inorganic composites
作者: 洪克昌
Ke-Chang Hung
關鍵字: 溶膠–凝膠法;木材–SiO2複合材;木材–TiO2複合材;熱分解動力學;階段式等應力法;Sol-gel;Wood-SiO2 composites;Wood-TiO2 composite;Thermal decomposition kinetics;Stepped isostress method
摘要: 
本研究利用甲基三甲氧基矽烷(Methyltrimethoxysilane,MTMOS)、甲基三乙氧基矽烷(Methyltriethoxysilane,MTEOS)、四乙氧基矽烷(Tetraethoxysilane,TEOS)以及異丙基氧化鈦(Titanium (IV) isopropoxide,TTIP)為反應藥劑,透過溶膠–凝膠(Sol-gel)法製備木材–無機複合材,除尋求其最適化條件外,並探討木材–無機複合材之無機物分布情形、物理機械性質、熱分解動力學以及潛變性質。試驗結果顯示,當含浸時間為3天時,木材–SiO2複合材中係以MTMOS/甲醇/醋酸莫耳比為0.12/1/0.08處理所得之重量增加率(Weight percent gain,WPG)最高;而木材–TiO2複合材係以莫耳比為0.12/1/0.02之TTIP/異丙醇/醋酸條件處理者最佳。另外,吸水試驗及抗彎性質試驗結果顯示,SiO2或TiO2無機物(WPG 20)均能有效提高柳杉試材之尺寸安定性;其中,又以木材–SiO2複合材改善效果較佳。再者,掃描式電子顯微鏡/能量分散光譜儀(Scanning electron microscope/energy dispersive spectrometer,SEM/EDS)之試驗結果則指出,木材–TiO2複合材中鈦元素多存在於細胞腔。而木材–SiO2複合材中矽元素之分布則會因其含水率不同而有所差異,以含水率9%柳杉試材所製備之無機複合材,其矽元素多存在於細胞壁;相對的,當試材為飽水狀態時,其矽元素除存在於細胞壁亦會填充於細胞腔內。同時,根據固態29Si-NMR之分析結果得知,以MTMOS製備木材–SiO2複合材之Si元素主要結構為T2及T3型態,顯示MTMOS複合材中會形成三次元網狀結構。
熱分解試驗主要係以熱重分析儀於氮氣環境下進行,並透過Friedman、Flynn-Wall-Ozawa(F-W-O)、modified Coats-Redfern(modified C-R)以及Starink四種等轉化率法評估其熱分解動力學。試驗結果顯示,以MTMOS所製備之木材–SiO2複合材中,當WPG達10、20以及30%時,其轉化率為10–70%之平均活化能分別為193–204、201–214以及209–213 kJ/mol;相對的,未處理柳杉試材之活化能僅為155–165 kJ/mol。此外,利用TTIP及TEOS所製備之木材–TiO2及木材–SiO2複合材,其平均活化能與MTMOS處理者相似。然而,由Avrami分析法所得之反應級數得知,木材之熱分解反應級數(0.52)均較木材–SiO2複合材及木材–TiO2複合材為高。另一方面,由階段式等應力法(Stepped isostress method,SSM)之試驗結果可以得知,不同SSM試驗條件之潛變主曲線具有高度一致性,且各組試材長期潛變曲線之趨勢與SSM預測之潛變主曲線相似,顯示SSM可用以評估木材及木材–無機複合材之長期潛變行為。同時,由結果得知,木材–無機複合材之潛變抗性較未處理木材為佳;其中,又以MTMOS所製備之木材–SiO2複合材(WPG 20)具有最低之時間依存(Time-dependent)模數衰減率。而由Eyring方程式計算所得之活化體積得知,木材之活化體積(0.856 nm3)較MTEOS(0.799 nm3)及TEOS(0.750 nm3)處理材(WPG 20)為高。綜合上述試驗結果可以得知,透過金屬烷氧化合物處理可以有效提高木材之尺寸安定性、熱安定性以及潛變抗性。

In this study, methyltrimethoxysilane (MTMOS), methyltriethoxysilane (MTEOS), tetraethoxysilane (TEOS), and titanium (IV) isopropoxide (TTIP) were used as reagents to prepare the wood-inorganic composites by sol-gel process. The optimal sol-gel condition, inorganic component distributions within the composites, physicomechanical properties, thermal decomposition kinetics, and creep properties were evaluated. The results revealed that, under impregnation time of 3 days, the solutions of MTMOS/methanol/acetic acid and TTIP/2-propanol/acetic acid with molar ratios of 0.12/1/0.08 and 0.12/1/0.02 exhibited the highest weight percent gain (WPG) for wood-SiO2 composite and wood-TiO2 composite, respectively. In addition, the dimensional stabilities and modulus of rupture (MOR) of wood-SiO2 composite and wood-TiO2 composite (WPG 20) were better than those of untreated Japanese cedar wood, especially for the wood-SiO2 composite. The scanning electron microscope/energy dispersive spectrometer (SEM-EDS) showed that the titanium were deposited principly in the cell lumens of wood-TiO2 composite, but the silicon deposition site within the composite was significantly dependent on the moisture content of wood. For instance, most silicon was deposited in the cell wall of conditioned wood (moisture content = 9%) after sol-gel process, while the silicon was deposited in both cell wall and cell lumen for the water saturated wood. According to the results of the 29Si NMR, two different siloxane peaks (T2 and T3) were observed, which supporting the MTMOS formed a network structure in the composite.
The thermal decomposition experiments were carried out in a TG analyzer under a nitrogen atmosphere, and four iso-conversional methods, including Friedman, Flynn-Wall-Ozawa (F-W-O), modified Coats-Redfern (modified C-R), and Starink, were used to determine the thermal decomposition kinetics. The results showed that the activation energies of thermal decomposition between 10% and 70% conversion were 147–172, 170–291, 189–251, and 192–248 kJ/mol for Japanese cedar wood and its SiO2 composites prepared from MTMOS with a WPG of 10, 20, and 30%, respectively. The average activation energies of wood-SiO2 and wood-TiO2 composites prepared from TEOS and TTIP were similar to the MTMOS treated one. However, the average reaction order of wood-inorganic composites was lower than that of untreated wood (0.52). On the other hand, according to the result of stepped isostress method (SSM), smooth master curves were obtained from different SSM testing parameters, and they fitted well with the long-term creep curves of wood and wood-inorganic composites. These results demonstrated that SSM could be used to evaluate the long-term creep behavior of wood and wood-inorganic composites. The creep resistance of wood-inorganic composites was greater than that of untreated wood. Among all wood-inorganic composites, the wood-SiO2 composite prepared from MTMOS with a WPG of 20% exhibited the lowest reduction in time-dependent modulus. According to the activation volume of specimens calculated by the Eyring equation, the activation volume of wood-SiO2 composite (WPG 20) prepared from MTMOS (0.799 nm3) and TEOS (0.750 nm3) were lower than that of untreated wood (0.856 nm3). Accordingly, the dimensional stability, thermal stability, and creep resistance of the wood could be effectively enhanced by metal alkoxides treatment.
URI: http://hdl.handle.net/11455/95730
Rights: 同意授權瀏覽/列印電子全文服務,2020-07-31起公開。
Appears in Collections:森林學系

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