【作者】 卿彦；

【导师】 吴义强；

【作者基本信息】 中南林业科技大学 ， 木材科学与技术， 2010， 硕士

【摘要】 随着天然林木材的日益匮乏及社会进步带来的人们对木质品的广泛需求,人工速生林木材已成为提供木材资源的主体,然而,其材质疏松、密度低、幼龄材含量高和干燥时易变形开裂严重影响了利用水平和附加值提高,制约了我国速生林的发展。近年来,硅系化合物,包括无机硅化合物如硅酸盐、氟硅化合物、氯硅化合物等,有机硅化合物如硅酸乙酯、甲基三乙氧基硅氧烷等广泛应用于速生林木材改性,得到的复合材料在物理力学、防腐抗虫、尺寸稳定、防火阻燃等方面都得到改善和增强。因此,本文在综合总结国内外的众多研究基础之上,以杨木为基材,分别采用溶胶-凝胶法和浸渍硅溶胶法制备了两类硅系化合物／杨木复合材料,且研究了含水率、基材预处理方式对复合材增重率及微观构造的影响。运用SEM表征了材料的微细构造,通过XRD、FTIR探讨了复合材各组分间的结合方式,采用TG分析了复合材的热性能,基于Doyle积分法构建了相关的动力学方程；同时综合比较分析了复合材的抗弯强度、弹性模量及表面硬度等物理力学性能,主要研究结论如下：(1)溶胶-凝胶法制备出的复合材增重率大于浸渍硅溶胶法,且随着基材含水率的增加,复合材增重率也呈现出增加的趋势。在浸渍硅溶胶处理过程中,不同的基材预处理方式对所得复合材的增重率有较大影响,先微波再偶联剂预处理后制备的复合材增重率最大,其次是偶联剂处理材,微波处理材次之,素材复合材增重率最小。(2)SEM观察发现,复合材保持了木材的多孔特性,反应生成的固体物质主要分布在木材的导管、木纤维、贯通导管与木纤维的纹孔及细胞间隙之间,且在木纤维中含量最多；在横切面上,它们以沉积的方式存在,而在纵切面上,它们与细胞壁物质结合,产生了物理吸附、氢键及共价键等化学键。(3)通过XRD分析表明,与杨木素材相比,复合材的衍射峰位置没有变化,只是衍射峰的强度有所减弱,生成的无定形态硅氧化合物没有改变纤维素的结构及晶面间距,但是影响了木材的结晶度。随着增重率的增加,衍射强度越来越弱,且对纤维素(100)结晶面影响最大,对(040)结晶面影响最小。FTIR分析发现,木材的基本特征吸收峰都没有变化,但是新的Si-O-Si键出现在复合材中,受硅氧基团与细胞壁纤维素生成的氢键影响,Si-O-Si键的所有振动都向高频区移动了30-40cm-1,然而,Si-O-C键由于生成量少且振动较弱,在光谱图上没有表现出来。(4)TG分析表明,复合材在热解阶段的反应温度区间变小,缩短了高温热解时间,促进炭化进行；质量损失率明显减少,木材的热稳定性提高,表现出一定的阻燃特性。热动力学分析表明,硅系化合物的引入,提高了热解阶段的活化能,降低了反应速率,在一定程度上缓解了木材的热解,对木材具有阻燃及保护作用。(5)溶胶-凝胶法制备的硅系化合物/杨木复合材的抗弯强度、抗弯弹性模量都小于杨木素材,但随着增重率的增大,复合材的抗弯性能逐渐增强。浸渍硅溶胶法制备的硅系化合物/杨木复合材的抗弯性能表现出溶胶-凝胶法相似的变化趋势,但是基材经过微波改性处理后的得到的复合材的抗弯弹性模量均高于杨木素材。两种方法所得的复合材的表面硬度都大于杨木素材,且增强幅度超过了30%。更多还原

【Abstract】 Plantation-grown wood with fast growing has become the main specie supplying the wooden resource accompanying the badly lackness of natural forest wood but widely demand for wooden product which is contributed to great social progress. However, the defects like loose and soft material quality, low wood density, and high percentage of juvenile wood and easy distortion and spilt when drying have badly affected its utilization level and increacement of added-value, which restricted the wide development of fast-growing forest in our country. In recent years, silicon compounds containing inorganic such as silicates, silicofluoride and chloro-silicon compounds and organic like tetraethoxysilane and triethoxysilane have been successfully applied to the wood modification. In general, the obtained composites have an increase in durability as well as dimensional and photostability, whereas the improvement of certain mechanical such as surface hardness, tensile strength, fire resistance and water uptake can be partly achieved. Therefore, the research progress and advance manufacture methods in this field at home and abroad were summed up, based on this, two kinds of silicon compound/polar wood composites were fabrication by sol-gel and dipping silicasol respectively in this study, and the influence of moisture content and pretreatment approaches on the weight gain percentage (WPG) and microstructure were investigated. Moreover, microstructure of the composites were characterized by SEM, binding ways among various components were detected through FTIR and XRD, thermal properties of these composites were measured by TG, based on this and combined with Doyle method, the related thermokinetic equation were formulated. Meanwhile, physical-mechanical properties contaning bending strength (MOR), modulus of elasticity in static bending (MOE) and surface hardness were analyzed comprehensively, the results are as follows:(1) Composites which manufactured by sol-gel have a higher WPG than that by dipping silicasol, for the former, the WPG trends to increase along with the increase of moisture content in wood matrix, and for the latter, different pretreatment approaches have significant effect on the WPG, composites treated by microwave primarily and then by silane coupling agent have a highest WPG, then that treated by silane coupling agent, and then by microwave, the last is the ones without any pretreatment. (2) SEM observation showed that composite materials maintained the wood porous characteristics, solid materials from the reaction mainly existed in vessel, wood fiber, the pits which are cross vessels and fiber and the space between cells, and the content in the wood fiber was the highest; they existed by means of deposition in transverse section while in the way of closely connecting with the cell wall material in longitual section, producing hydrogen bond and chemical bonding like covalent bond.(3) XRD analysis showed that compared with the poplar, the position of the diffraction peak of composite material has not changed but the intensity reduced and the obtained amorphous silicon oxide has not changed the structure and interplanar spacing of cellulose while affecting the crystallinity of wood. With the increase in WPG, diffraction intensity gradually became weaker and it has greatest impact on (100) crystal plane of cellulose and the least on the (040) crystal plane. FTIR analysis showed that the basic characteristic absorption peaks o.f timber has not changed, but the new Si-O-Si bond appeared in the composite material, and all vibrations of Si-O-Si bond moved 30-40cm-1 towards the high frequency area with the effects of hydrogen bonds derived from the reaction of silicon-oxygen groups and cellulose on cell wall, however, Si-O-C bond was not present in the spectrum because of its little amount and weak vibration.(4) TG analysis showed that the reaction temperature range of the composite in pyrolysis phase was shortened, as well as the high-temperature pyrolysis time, which promoted carbonization process. What’s more, the mass loss rate decreased obviously, this hinted the improvement of thermal stability and a certain degree of flame-retardant effect. Thermokinetic studies have shown that the introduction of silicon compounds enhanced the activation energy in pyrolysis stage and reduced the reaction rate, and exhibited fire-retardant and protective effect on wood to a certain extent.(5) MOR and MOE in the composite prepared by both sol-gel are less than that of poplar wood, however, the MOR value increases along with the increasement of WPG, as well as by dipping silicasol. Hardness of these two kinds of composites was higher than polar wood that without any treatment by 30 percent.更多还原