摘要
木材是一种生态环境材料,可再生,是可持续利用的材料。但是,木材本身存在着许多缺陷,如干缩湿胀、耐腐性差、易燃烧等,特别是速生木材的缺陷尤为显著。因此,通过对木材材质的改良,实现木材的高效利用,既具有重要理论价值,同时具有广阔的应用前景。
本论文正是在这种基础上,选择南美龙凤檀进行无机化改性研究,通过在南美龙凤檀木材微纤丝间隙和纤维的胞腔中沉积纳米二氧化硅制备二氧化硅/木材复合材料,最终达到提高木材的尺寸稳定性、表面硬度、剪切强度、压缩强度和阻燃性性能目的。首先试验比较研究了木材预处理与否、微波干燥和烘箱干燥、溶胶-凝胶法和原位形成法两种二氧化硅引入方法以及性能测试评价方法等。初步的实验表明通过对南美龙凤檀的预先用无水乙醇浸泡处理,而后进行微波干燥处理,放到干燥箱中冷却到室温后放入蒸馏水中浸泡,最后进行木材原位复合处理形成的二氧化硅/木材复合材料物理性能综合表现最好。这是因为乙醇浸泡预处理能够溶出木材中含有的树脂、树胶和其他一些堵塞或半堵塞木材导管和纹孔等木材传导组织的有机物,可以疏通木材的流体通道,提高浸渍效率和阻燃性能;而微波的快速干燥也能够打通更多的连通空隙;这些都有利于更多的二氧化硅通过原位生成的方式填充到木材微纤丝间隙和纤维的胞腔中,从而使处理后木材的综合性能更好。
随后研究了微波干燥功率、微波干燥时间间隔、微波处理时间和配方等实验参数对二氧化硅/木材性能的影响,确定了最优化实验条件是:微波功率800W,微波干燥时间4min,微波处理时间间隔4min,生成二氧化硅的配方正硅酸乙酯、无水乙醇、冰乙酸摩尔比1:1:0.01。经过最优化条件处理的南美龙凤檀与未处理原木性能相比,吸水率从未处理的7.85%下降到2.16%,表面硬度从428 kgf/mm2提高到了575 kgf/mm2,剪切强度从13.02Mpa提高到18.35Mpa,压缩强度从100.05Mpa提高到128.47Mpa,燃烧后失重率从17.58%下降到5.87%,阴燃时间从99.58秒下降到3.58秒。
对复合后的样品进行红外分析,观察到了硅氧官能团的振动峰,说明的确有含硅氧成分进入了木材内部;通过高倍光学显微镜和场发射扫面电镜观察,在木材断面的微纤丝间隙和纤维的胞腔中观察到了纳米二氧化硅的颗粒,进一步说明经过实验处理纳米二氧化硅的确沉积在了南美龙凤檀木材微纤丝间隙和纤维的胞腔中,充分解释了二氧化硅无机改性的南美龙凤檀木综合性能提高的原因。
Wood is a environment ecological, renewable material that can be sustainably used. However, there are many defects, such as dry shrinkage and wet expansion, poor decay resistance, and easy to burn. Therefore, the improvement of wood materials will be of defective material for wood, wood materials through improvements in the achievement of the efficient use of timber. Therefore, modification of the timber, not only has important theoretical value, but also has broad application prospects.
It is in this context, this paper based on the choice of cumaru for modification of inorganic, through the deposition of the nano-silica both the wood and fiber microfibril gap compounded silica / wood composites. Ultimately to improve wood dimensional stability, surface hardness, shear strength, compressive strength and flame retardant. First of all, a comparative researched of the timber pre-treatment, microwave drying and oven drying, the introduction of silica through sol-gel and in situ-forming methods, and evaluation methods such as performance testing. Preliminary experiments showed that the cumaru was soaking with ethanol, microwave drying and then put in drier after cooling to room temperature, soaked in distilled water, finally to the formation silicon dioxide/wood composite material, physical properties of the best overall performance. This is due to the dissolution of ethanol pretreatment soaking timber containing the resins, gums and other wood plug or semi-plugged ducts and pits organizations, such as organic conductive timber, the fluid timber can be clear-channel and improve the efficiency of impregnation; Rapid microwave drying can also open up more gaps in connectivity; these are more conducive to in situ generated silica way through the wood filler and fiber microfibril gap in the cell, so that the treated wood better overall performance.
Then studied the power of microwave drying, microwave drying time and interval, microwave formula, experimental parameters on the silicon dioxide / wood properties to determine the optimal experimental conditions are: microwave power of 800W, microwave processing time interval 4min, microwave processing time 4min, TEOS:ETOH:CH3COOH=1:1:0.01. After the optimum conditions to deal with the cumaru performance compared with the untreated wood, water absorption fell from 7.85% to 2.16%, the surface hardness increased from 428 kg/mm2 to 575 kg/mm2, shear strength from 13.02Mpa to 18.35Mpa, compressive strength from 100.05Mpa to 128.47Mpa, combustion weight loss rate dropped from 17.58% to 5.8%, flameless combustion time dropped from 99.58s to 3.58s.
After the composite infrared analysis of samples, observed in Si-O vibration peaks of functional groups that have silicon and oxygen composition within the timber; Through high-optical microscope and SEM, in the timber section of the microfibril and fiber space cell observed nano-silica particles. The further experiments are indeed nano-silica deposited on the cumaru microfibril and fiber space cell. So we can explaine that the cumaru by modification of inorganic improved physical properties.
引文
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