木材保护用笼型倍半硅氧烷的合成

木材作为一种重要的建筑材料,本身含有丰富的纤维组织、微孔和导管,由毛细作用吸收空气中的水分。由于受自然环境(如光照、湿度和温度等)的影响,木材易发生湿胀干缩而导致开裂、形变,从而影响其观赏和使用价值,缩短其使用寿命。笔者以使木材表面具有疏水功能为出发点,以硅溶胶和甲基三乙氧基硅烷(MTES)为原料,采用一步法聚合反应得到笼型倍半硅氧烷低聚体(MS)。通过扫描电子显微镜、傅里叶红外光谱、X射线衍射对各合成条件下所得MS的形貌和结构进行了分析,得到的MS颗粒为表面带有羟基基团的微米级、光滑的立方晶体,其最佳合成条件是把1.2 g MTES和0.2 g硅溶胶置于30 mL无水乙醇中,加入20 mL碱催化剂(0.1 mol/L NaOH),室温下超声反应2.5 h。经聚合得到的MS溶液处理后的木材表面构建起微米级粗糙结构,且MS颗粒填充在木材起吸收水分的细胞腔、导管、纹孔等结构中。通过接触角测试得到用MS溶液处理后的木材具有良好的疏水性,接触角达到141.5°。反应所得溶液可直接使用,合成工艺简单,具有良好的应用前景。

Synthesis of cage silsesquioxane for wood protection

As an important building material,wood is rich in fibrous tissue,micropores and vessels,and absorbs mois?ture in air by its capillary.Due to the influence of the natural environment(such as light,humidity,and tempera?ture),wood is prone to wet expansion and shrinkage,so cracking and deformation affect the use value and ornamental value,which greatly shortens the service life.The purpose of this study was to make the wood surface to have a hydrophobic function,using silica sol and methyltriethoxysilane(MTES)as raw materials,anhydrous ethanol as solvent,0.1 mol/L NaOH as catalyst,and using ultrasonic apparatus one?step polymerization reaction to obtain the micron oligomeric semisiloxane(MS)oligomers.MS under different conditions was synthesized by controlling reac?tion time,feeding ratio of raw materials,amounts of solvent and alkali catalyst.The morphology and structure of MS obtained under various synthesis conditions were analyzed by scanning electron microscope,Fourier transform infrared spectroscopy,and X?ray diffraction.The obtained MS particles were micron?sized,smooth cubic crystals with hydrox?yl groups on the surface.The best synthesis conditions were 1.2 g MTES and 0.2 g silica sol were placed in 30 mL ab?solute ethanol solvent,20 mL alkali catalyst(0.1 mol/L NaOH)was added,and ultrasonic reaction was performed at room temperature for 2.5 h.The reasons for the different morphologies of MS synthesized under different conditions were analyzed.Too long reaction time would cause agglomeration of products,too much alkali would cause product depolymerization,too much MTES added would cause condensation reaction of MTES,and too much ethanol would hinder the hydrolysis of MTES.A micron?scale rough structure was constructed on the wood surface treated with the MS solution by polymerization,and MS particles were filled in the structures such as cell cavities,vessels and pits that absorb water in the wood.The contact angle test showed that the wood treated with the MS solution had good hy?drophobicity,and the contact angle reached 141.5°.A large number of uniformly distributed Si elements were ob?served on the wood surface after the MS treatment by the energy spectrometer,indicating that MS was uniformly distributed on the wood surface.MS was adsorbed on the wood surface by silicon?oxygen bonds.The existence of silicon?oxygen bonds improved the ultraviolet corrosion resistance of wood.As a simple method,the solution obtained by the reaction can be used directly for the synthesis process,and it has good application prospects.