| 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.
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