疏水型醇酸树脂/SiO2有机无机杂化材料的制备与性能

基于溶胶凝胶(sol-gel)工艺,采用两步法,以正硅酸乙酯(TEOS)、甲基三乙氧基硅烷(MTES)、己二酸、聚乙二醇400(PEG 400)为原料,制备了疏水型醇酸树脂/SiO2有机无机杂化材料。MTES的Si-CH3基团赋予材料的疏水性能,随着MTES含量的提高,接触角θ增大,当MTES(质量分数,下同)超过15%时,接触角θ增大不明显,并最终稳定在126°左右。红外图谱(FT-IR)和X射线光电子能谱(XPS)分析结果显示,硅溶胶与醇酸树脂间发生了的杂化反应,形成了Si-O-C键。DSC分析结果显示,随SiO2%的提高,杂化材料的耐热性能提高。     

疏水型多孔PVA/SiO2有机无机杂化材料的研究

以正硅酸乙酯(TEOS)、甲基三乙氧基硅烷(MTES)、聚乙烯醇(PVA)为原料，基于溶胶凝胶工艺制备出疏水型多孔PVA／SiO2有机无机杂化材料。杂化材料内部的硅氧链与PVA链相互交织，形成杂化网络结构，具有增强增韧的效果。杂化材料在热处理过程中，小分子逸出产生的微孔和材料表面面外的甲基，赋予了材料的透气疏水性能，可用于制备性能优良的环保型包装薄膜、农用地膜等功能复合材料。     

溶胶-凝胶法改性SiO2膜的润湿性与水汽稳定性

以甲基三乙氧基硅烷(MTES)替代部分正硅酸乙酯(TEOS)作为前驱物,用溶胶-凝胶法制备了MTES改性二氧化硅溶胶和二氧化硅膜,研究了憎水基团的添加量对溶胶体系的稳定性和对二氧化硅膜润湿性以及水汽稳定性的影响.结果表明,随MTES/TEOS摩尔比增大,二氧化硅溶胶的稳定性降低,改性二氧化硅膜的表面自由能显著减小;表面润湿性降低,主要是表面张力中极性力的贡献,FTIR分析表明,这是由于二氧化硅颗粒表面-CH3非极性基团增加所致;在潮湿环境中陈化时,二氧化硅膜接触角的变化及吸水率随MTES/TEOS摩尔比增大而减小,疏水性二氧化硅膜的MTES/TEOS宜为0.8～1.0;AFM形貌分析表明陶瓷支撑体上的二氧化硅薄膜连续,膜表面较光滑、平整.     

Synthesis of paramagnetic iron incorporated silica aerogels by ambient pressure drying

The iron incorporated silica aerogels were prepared under ambient pressure drying through a two-step sol-gel route by using tetraethoxysilane (TEOS), methyltriethoxysilane (MTES) and ferric nitrate as co-precursors, and hexamethyldisilazane (HMDZ) as a surface modification reagent. Compared with the silica aerogels modified by trimethylchlorosilane (TMCS) or HMDZ, the iron incorporated silica aerogels exhibited good integrity, paramagnetic behavior, and highly hydrophobicity which could be maintained up to 650 °C. However, the introduction of iron into silica aerogels resulted in more apparent volume shrinkage, higher density, lower porosity, and smaller pore diameter. It was found that a large amount of water was retained in the silica network, accordingly, the water containing iron oxides (Fe–OH) were more readily formed than water free iron oxides (Fe–O), which adversely affected the physical properties of iron incorporated silica aerogels.     

实验条件对SiO2-MTES-CTAB纳米疏水薄膜的影响

以正硅酸乙酯(TEOS)为硅源,采用溶胶-凝胶技术,通过两步酸法控制实验条件引入有机硅烷甲基三乙氧基硅烷(MTES)和表面活性剂十六烷基三甲基溴化氨(CTAB),制备了疏水型SiO2前驱体溶胶.以旋涂法成膜出SiO2-MTES-CTAB纳米疏水薄膜,研究了正硅酸乙酯与甲基三乙氧基硅烷不同的混合比以及不同的热处理温度等对纳米疏水薄膜的影响,并且分析了纳米疏水薄膜的表面形态.研究表明,利用有机基团甲基三乙氧基硅烷改性SiO2溶胶和薄膜的热处理温度对制备的SiO2基纳米疏水薄膜的性能以及表面形态都具有非常重要的影响.     

憎水二氧化硅膜的制备、表征及水热稳定性研究

用甲基三乙氧基硅烷(MTES)代替部分正硅酸乙酯(TEOS)作为前驱物,通过共水解缩聚反应可制得甲基修饰的二氧化硅膜.通过TGA、FTIR以及气体渗透等测试手段对甲基修饰的SiO₂膜进行研究,发现随着MTES/TEOS摩尔比例的增大,二氧化硅膜的憎水性能逐渐增强,当MTES/TEOS达到0.8时,二氧化硅膜的孔表面几乎不再吸附水气.氢气在MTES/TEOS为1的支撑体二氧化硅膜的输运受温度的控制,200℃时H₂的渗透率达到6.0×10^-7mol·m^-2.Pa^-1·s^-1,H₂/CO₂分离系数达到6.0,于200℃以及水蒸气压力为3564Pa的环境中陈化近110h后H2渗透率基本保持不变,H₂/CO₂分离系数有所增大,说明经过甲基修饰的二氧化硅膜比纯二氧化硅膜具有更好的水热稳定性.     

Study on the non-isothermal crystallization behaviors of PA6/silica nanocomposites prepared by the sol–gel process

A organic–inorganic PA6/partially functionalized silica hybrid nanocomposites was prepared by caprolactam polymerized and silica nanoparticles in situ gernerated through condensation of partially functionalized silicic acid, which was prepared through hydrolysis of tetraethoxysilane (TEOS) and 3-glycidoxypropyltrimethoxysilane (GPTES), in one process. The non-isothermal crystallization behaviors of pure PA6, PA6/unfunctionalized silica (PA6S) and PA6/functionalized silica (PA6FS) hybrid materials were investigated by differential scanning calorimetry (DSC). Two methods, namely, the Avrami and the Mo, were applied to describe the crystallization process of these three materials. DSC results showed that the crystallization rates of PA6FS is faster than that of pure PA6 and PA6S at the same cooling rate, the nano-silica particles functionalized by GPS in hybrid material acted as more effective nucleation agents, and the crystallization rates of all these samples increased with the cooling rate increasing. XRD results indicated that the addition of functionalized nano-silica particles favored the formation of the γ crystalline form.     

Temperature dependent microstructure of MTES modified hydrophobic silica aerogels

Hydrophobic silica aerogels were prepared using a single step sol-gel process followed by ethanol supercritical drying. Using tetraethoxysilane (TEOS) as a precursor and ammonium hydroxide as a catalyst the aerogel surface was chemically modified with methyltriethoxysilane (MTES). A MTES/TEOS molar ratio of 0.5 (M5) was used. The microstructure of the surface modified aerogels was evaluated as a function of heat treatment temperature over a range of 200-500 °C. The thermal stability was analyzed by simultaneous thermogravimetry and differential scanning calorimetry (TG-DSC) and the microstructure was evaluated by physisorption analysis (BET) and scanning electron microscopy (SEM). The chemical composition and hydrophobicity/hydrophilicity of the aerogels were investigated by Fourier Transform-Infrared (FT-IR) spectroscopy. The M5 aerogels, which were initially hydrophobic, exhibited partial hydrophilicity at treatments above 244.5 °C and complete hydrophilicity above 429.9 °C. The surface area of the aerogels ranged from 776.65-850.20 m²/g. Pore size increased after heat treatment, ranging from 16.25 to 18.52 nm vs. an initial pore size of 14.71 nm. The maximum pore size of 18.52 nm was found at the lowest heat treatment temperature (~ 200 °C). Heat treatment had a mixed effect on the pore volume, as pore volumes decreased at lower treatments (~ 200-400 °C) and increased at higher heat treatments (~ 450-500 °C) relative to the untreated aerogels. With initial heat treatment the Si-CH₃ group began to oxidize to Si-OH. Aerogels heated above 429.9 °C exhibited hydroxyl polymerization leading to aerogels with large particles and a dense microstructure.     

Tunable adsorption behavior of silica materials in the removal of dense non-aqueous phase liquids

Mesoporous silica material has dual characteristics including adsorption of organic contaminants and transport through the sediments, making it an ideal material as a platform for zerovalent iron particles in the in situ remediation of dense non-aqueous phase liquids such as trichloroethylene. In this paper, tunable adsorption behavior of silica materials was quantitatively investigated by batches of equilibrium experiments. Significant enhancement in adsorption capacity was observed on mesoporous organo-silica particles as a consequence of the functionalization of particle surface from hydrophilicity to hydrophobicity. The fact that there is a wide difference in adsorption capacities between the non-functionalized mesoporous silica (MCM-41) and the alkyl-functionalized mesoporous silica prompted a study to control adsorption levels by simply adjusting the amount of methyl triethoxysilane (MTES) precursor in a mixture of MTES and tetramethoxysilane. In comparison with the most commonly used adsorbent activated carbon, the higher yield of adsorbent of 83 ± 2.6% was observed for mesoporous methyl silica particles. Particle characterizations were performed by means of X-ray powder diffraction, transmission electron microscopy, scanning electron microscopy, Brunauer–Emmett–Teller, thermogravimetric analysis and Fourier transform infrared measurements.     

Synthesis, structure and properties of a novel hybrid bimodal network elastomer with inorganic cross-links: The case of silicone–nanocrystalline titania

We describe an innovative concept of synthesizing a novel hybrid bimodal network elastomer with high strength–high ductility combination involving utilization of functionalized nanocrystalline titania as short-chain cross-links between neighboring elastomer chains. This subject is germane both fundamentally and from an application viewpoint. Silicone rubber is selected as the model elastomer. The short-chain cross-links are acrylic acid functionalized nanocrystalline titania that are an integral component of bimodal network structure of the elastomer. To delineate and separate the effects of functionalization from nanoparticle effects, a relative comparison is made between silicone rubber–titania nanocomposite (i.e. containing dispersion of titania as a reinforcement filler) and silicone rubber–titania hybrid network elastomer (i.e. titania as short chain cross-links). An important finding is that the effect of functionalized titania present as short chain cross-links is far more significant than non-functionalized titania present as reinforcement filler, on mechanical behavior. This is presently ascribed to the double bonds introduced to nanocrystalline titania via functionalization with acrylic acid that provide active sites for the cross-linking reaction resulting in inorganic bridging chains. The basic physical mechanisms that govern elastic recovery in hybrid bimodal network elastomer with short chain cross-links of functionalized nanocrystalline inorganic particles are discussed. The hypothesis of the study described here is that the hybrid bimodal network elastomer with short chain cross-links of functionalized nanocrystalline inorganic particles modifies the unimodal long chain network elastomer with consequent increase in modulus and high strength–ductility combination.     

Bioactivity of wollastonite/aerogels composites obtained from a TEOS–MTES matrix

Organic–inorganic hybrid materials were synthesized by controlled hydrolysis of tetraethoxysilane (TEOS), methyltrimethoxysilane (MTES), synthetic wollastonite powders and polydimethylsiloxane (PDMS) in an ethanol solution. Aerogels were prepared from acid hydrolysis of TEOS and MTES with different volume ratio in ethanol, followed by addition of wollastonite powder and PDMS in order to obtain aerogels with 20 wt% of PDMS and 5 wt% of CaO of the total silica. Finally, when the wet gels were obtained, they were supercritically dried at 260 °C and 90 bar, in ethanol. In order to obtain its bioactivity, one method for surface activation is based on a wet chemical alkaline treatment. The particular interest of this study is that we introduce hybrid aerogels, in a 1 M solution of NaOH, for 30 s at room temperature. We evaluate the bioactivity of TEOS–MTES aerogel when immersed in a static volume of simulated body fluid (SBF). An apatite layer of spherical-shaped particles of uniform size smaller than 5 microns is observed to form on the surface of the aerogels after 25 days soaking in SBF.     

Synthesis and properties of chitosan/SiO2 hybrid materials

This study primarily aims to explore the strength and thermal properties of various hybrid materials that are made of tetraethoxysilane/vinyltriethoxysilane (TEOS/VTES) and chitosan in different weight ratios. It is confirmed, from micro Fourier transform infrared (micro FT-IR) and nuclear magnetic resonance (NMR) analysis, that hydrogen bonds emerge between chitosan and SiO₂ in hybrid materials. With the addition of more VTES and TEOS, the surface of the hybrid material features thick granules. In addition, the mechanical performance and thermostability of both types of hybrid are better than pure chitosan. The former is enhanced with an increasing amount of TEOS until it exceeds 2.4 g and the latter is also improved with an increasing amount of TEOS.     

Synthesis of hydrophobic aerogels for transparent window insulation applications

Abstract

The present paper deals with the synthesis of hydrophobic aerogels using methyltrimethoxysilane (MTMS) as a hydrophobic agent for transparent window insulation applications. The molar ratio of methanol (solvent), water, and ammonia (catalyst) to the tetramethoxysilane (precursor) MeOH/H₂O/NH₄OH/TMOS was fixed at 12/4&/3·6×10^-3/1 throughout the experiments and the MTMS/TMOS molar ratio M was varied from 0 to 1·55. After gelation, the alcogels were dried supercritically using the high temperature alcohol method. It has been found that lower (<0·26) M values resulted in highly transparent (optical transmission >90% for a 10 mm thick sample at 800 mm wavelength) and negligible volume shrinkage (<2%) but less hydrophobic aerogels whereas higher (>1·03) M values resulted in semitransparent (<20% optical transmission of 800 nm for a 1 cm thick sample) aerogels with >10% volume shrinkage but excellent hydrophobicity. A good compromise of acceptable optical transmittance (～85% optical transmission at 800 nm for a 1 cm thick sample), hydrophobicity with 42 kg m^-3 bulk density, and negligible volume shrinkage were obtained at M≈0·70. Hydrophobicity of the aerogels was tested by measuring the contact angle between a water droplet and the aerogel surface. The aerogels were characterised by infrared spectroscopy, bulk density, optical transmittance, and thermal conductivity measurements.     

原位乳液接枝法制备聚丁二烯/SiO_2杂化材料

在聚丁二烯(PB)胶乳中进行乳液自由基反应,将乙烯基三乙氧基硅烷(VTES)接枝到聚丁二烯分子链上,制备了聚丁二烯/SiO2杂化材料。运用硅含量、交联率、傅立叶变换红外光谱(FT-IR)、热失重分析(TGA)对产物结构进行了表征,考察了产物多种性能的变化情况,并探讨了杂化材料的形成机理。结果表明,VTES通过共价键合在PB链上,并与水解缩合形成的硅核连接,利用率达88.6%;接枝后产物凝胶率提高,分解速率降低,力学性能如门尼黏度、拉伸强度和断裂伸长率均显著改变。     

Superhydrophobic sodium silicate based silica aerogel prepared by ambient pressure drying

The superhydrophobic silica aerogel was prepared by using less expensive sodium silicate as a main silica source through a cost-effective and simple route via ambient pressure drying. The sodium impurity was first eliminated by mixing sodium silicate with a co-precursor methyltriethoxysilane (MTES) followed by ion exchange process. The hydrogel was formed by gelation and the alcogel was further obtained by alcoholization of the hydrogel. The surface of alcogel was modified by reacting with trimethylchlorosilane (TMCS) diluted in n-hexane. It was suggested that MTES accelerated water expelling from the hydrogel, while TMCS modified the surface of silica network by replacing Si–OH with Si–C. As a result, the obtained silica aerogel exhibited excellent physical properties with less than 10% volume shrinkage. The density, surface area and cumulative pore volume were 0.12 g cm⁻³, 684.44 m² g⁻¹, and 3.55 cm³ g⁻¹, respectively. The optical transmission reached 82.8% with the water contact angle of 146°.     

聚对苯二甲酸乙二醇酯滤料超疏水表面的制备及性能

以聚对苯二甲酸乙二醇酯(PET)滤料为基体材料,正硅酸乙酯(TEOS)和甲基三乙氧基硅烷(MTES)为改性剂,采用溶胶-凝胶法,制备超疏水性PET滤料。在此基础上,采用场发射扫描电子显微镜(FESEM-EDS)、傅里叶变换红外光谱仪(FTIR)和接触角测试仪研究PET滤料改性前后的微观形貌、表面组成以及接触角等参数。研究表明:改性前后滤料微观孔隙率基本不变,TEOS改性的PET(T-PET)滤料由于形成大量亲水性的—OH基团,呈现完全润湿性;MTES改性的PET(M-PET)滤料表面存在疏水性的—CH₃基团,呈现高疏水性;TEOS和MTES共同改性的PET (MT-PET)滤料表面由于大量疏水性的—CH₃基团,且有大量的含有—CH₃基团SiO₂纳米粒子沉积在纤维表面,降低了滤料表面能,形成纳米级粗糙、褶皱甚至凸起形态;MT-PET的静态接触角(WCA)为(158.8±1.2)°,流失角(WSA)为(6.9±1.5)°,达到超疏水状态。此外,通过喷涂湿粉尘和水中浸泡(室温)滤料对比试验,表明MT-PET滤料具有良好的自清洁性能与稳定性。综上,本文中MT-PET超疏水滤料的制备,对于高湿环境下的袋式除尘材料的研究开发具有潜在价值。      

Preparation and characterization of silica/fluorinated acrylate copolymers hybrid films and the investigation of their icephobicity

Inexpensive hydrophobic and icephobic coatings and films were obtained by a simple method. These coatings were prepared by mixing silica sol and fluorinated acrylate copolymers. There was a phase separation process in the film-forming which can provide the excellent performance. Small amount (about 2 wt.%) of fluorinated (methyl) acrylate was used in all of these coatings. The coatings were eco-friendly by using ethanol as the solvent system. Scanning electron microscopy, atomic force microscope, energy dispersive X-ray fluorescence spectrometer, water contact angle, thermal gravimetric analysis and tests of adhesion and hardness had been performed to characterize the morphological feature, chemical composition, hydrophobicity and icephobicity of the surface, thermal stability and mechanical properties of the coatings. The results showed that the films had good hydrophobicity, high thermal stability and excellent mechanical properties of adhesion strength and pencil hardness. Furthermore, by testing their properties of delaying water droplet from icing, it was found that ice formation was delayed for 90 min compared with the glass surface at − 5.6 °C. The hybrid coatings may be suitable for large-scale and practical application owing to its flexibility and simplicity.     

Synthesis of silicon carbide through the sol-gel process from different precursors

Silicon carbide (SiC) was synthesised from silicon alkoxides and various carbon sources. Tetraethoxysilane (TEOS), methyltriethoxysilane (MTES) and a mixture of TEOS and MTES were hydrolysed in the presence of phenolic resin, ethylcellulose, polyacrylonitrile (PAN) and starch to incorporate the gel into the carbon source in the silica network. The gel thus obtained was carbonized at 800°C in an argon atmosphere to obtain the mixture of silica and carbon which when heated to 1550°C in argon yielded silicon carbide. The characterization of the product by X-ray, FTIR and SEM showed it to be β SiC with different crystallite and grain sizes. The difference in the crystallite and grain sizes is attributed to the nature of the carbon source. The density of the SiC obtained by the sol—gel process was found to be lower than the values reported for SiC and this is ascribed to the porous nature of the products generally obtained by this process.     

Hydrophobicity and physical properties of TEOS based silica aerogels using phenyltriethoxysilane as a synthesis component

The experimental results on the hydrophobic and physical properties of tetraethoxysilane (TEOS) based silica aerogels by incorporating phenyltriethoxysilane (PTES) as a synthesis component, are reported. The molar ratio of tetraethoxysilane (TEOS), ethanol (EtOH), water (0.001 M oxalic acid catalyst) was kept constant at 1:5:7 respectively while the molar ratio of PTES/TEOS (M) was varied from 0 to 0.7. After gelation, the alcogels were dried supercritically by the high temperature solvent extraction. For lower M values (<0.1), transparent and monolithic aerogels but for higher M values (>0.5) opaque and cracked aerogels were obtained. For M values in between 0.1 and 0.5, monolithic aerogels with decreasing optical transmission have been obtained. The hydrophobicity of the aerogels was tested by measuring the percentage of water uptake by the aerogels when exposed to 95% humidity at 40°C for 24 h and also by measuring the contact angle. The contact angle varied from 120 to 130° for M values from 0.1 to 0.5, respectively. It was found that as the M value increased, the hydrophobicity of the aerogels increased but the optical transmission decreased from 60% to 5% in the visible range. The thermal conductivity and the specific heat of the aerogels found to decrease with the increase in M values. In order to determine the thermal stability in terms of retention of hydrophobicity of the aerogels, they were heat treated in air in the temperature range of 25–600°C. The hydrophobic aerogels are thermally stable upto a temperature of 520°C, which is the highest value ever reported, and above this temperature the aerogels become hydrophilic. The chemical bonds, responsible for the hydrophobic nature of the aerogels, have been identified by Fourier transform infrared spectroscopy (FTIR). The aerogels have been characterized by density, optical transmission, scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and differential thermal analysis (DTA).     

以甲基三乙氧基硅烷为原料制备疏水性整体气凝胶的研究

以甲基三乙氧基硅烷(MTES)为原料,通过两步水解以及超临界干燥制备疏水性整体气凝胶,通过改变凝胶形成过程中的酸碱浓度、原料比例等因素,制备孔结构特性不同的气凝胶。通过对气凝胶样品进行BET分析仪、压汞仪、热重分析仪和透射电镜等分析,考察各种因素对气凝胶孔结构的影响。