Structure of silane layer formed on silica particle surfaces by treatment with silane coupling agents having various functional groups

The surface treatment of spherical silica particles with silane coupling agents having various organic functional groups was conducted and the effect of the alkoxy group number on the molecular flexibility of the silane chain with multilayer coverage was investigated using ¹H-pulse nuclear magnetic resonance spectroscopy. The silica particles were treated with 2-propanol solution and heated at 120?°C for 24?h after solvent evaporation to accelerate the polycondensation reaction of silanol groups. For multilayer coverage, flexible linear chain and rigid network structures were expected to form on the surface from the di- and trialkoxy structures, respectively. However, the rigid network structure was formed from both the di- and trialkoxy structures with glycidoxy, amino, and methacryloxy functional silanes. Ring opening of the epoxy group occurred, followed by reaction to form the network structure, even with the dialkoxy structure of the glycidoxy functionality. Ring opening of the epoxy group could be reduced by pH adjustment of the treatment solution and the linear chain structure was formed from the dialkoxy structure. In the case of amino and methacryloxy functional groups, hydrogen bonds were formed between the amino or methacryloxy groups and the silanol groups on the silica surface or silane molecules.     

Influences of the alkoxy group number and treatment condition on the structure of glycidoxy functional silane-treated layer on silica particles analyzed by 1H pulse NMR

The surface treatment of spherical silica particles using a silane coupling agent with a glycidoxy group was conducted and the effect of the alkoxy group number on the molecular mobility of the silane chain was investigated by ¹H pulse nuclear magnetic resonance (NMR). Silanes with di-alkoxy and tri-alkoxy structures were used, and the silica particles were treated with 2-propanol solution and heated at 120?°C for 24?h after solvent evaporation. The surface coverage of the silica surface was in the range from two to three layers. For multilayer coverage, linear chain and network structures were expected to form on the surface by polycondensation reaction using the di- and tri-alkoxy structures, respectively. However, the relaxation times for silane chains with both di- and tri-alkoxy structures measured by pulse NMR were short, which indicates that both silane chains formed rigid network structures. Fourier transform infrared spectroscopic analysis revealed that ring opening of the epoxy group occurred, followed by reaction to form the network structure, even with the di-alkoxy structure. Ring opening of the epoxy group could be reduced by setting the heating temperature at 80?°C. There was a significant difference in flexibility between the silane-layers with di- and tri-alkoxy structures after heating at 80?°C, as reflected by the relaxation time.     

Surface structure of silane-treated glass beads and its influence on the mechanical properties of filled composites

The surface treatment of glass beads, chosen as a model filler, was carried out using four different silane coupling agents with multilayer coverage. For this purpose, silanes having an aminopropyl or a methacryloxypropyl group as an organofunctional group with di- or tri-alkoxy structures were used. The amount of silane detected on the bead surface was four to six times that required for a monolayer coverage. The topography of the silane layer on the bead surface was observed using an atomic force microscope. The topography was strongly affected by the composition of the silane solution and the number of alkoxy groups in the silane. The effects of the organofunctional group and the number of alkoxy groups of the silanes on the mechanical properties of bead-filled poly(vinyl chloride), chosen as a typical ductile polymer, were investigated. A higher yield stress was observed for the silane with an aminopropyl group than for that with a methacryloxypropyl group. Furthermore, for each organofunctional group, the yield stress was higher for the silane with a dialkoxy structure than for that with a trialkoxy structure. However, their effects on the elongation-at-break were contrary to the above tendencies.     

The Influence of pH on the Hydrolysis Process of γ-Methacryloxypropyltrimethoxysilane,Analyzed by FT-IR,and the Silanization of Electrogalvanized Steel

Silanes are commonly used as coupling agents to enhance the adhesion between polymeric and inorganic materials. Once silane hydrolysis has taken place, the condensation of the silane on the substrate surface should follow. Optimum hydrolysis conditions will depend on the type of silane and the process conditions of the solution. The pH is particularly important as it has a significant effect on the hydrolysis process. This paper deals with the hydrolysis process of 1 vol% γ-methacryloxypropyltrimethoxysilane (MPS) in aqueous solution at different pHs (2, 4, 6, 8 and 10). Because the hydrolysis rate is a function of pH, hydrolysis times, ranging from 2 min to 48 h, were studied. Fourier transform infrared spectroscopy was used to evaluate the chemical modifications produced by changing the hydrolysis time. The disappearance of the infrared band due to the Si–O–C groups and the appearance of the bands due to the Si–OH bonds were studied. It was shown that longer times were necessary for complete hydrolysis, under almost neutral pH conditions. On the other hand, the Zn-electrocoated steel was silanized with MPS under an optimum pH and the hydrolysis time conditions and the resulting surfaces were analysed by Reflection–Absorption Infrared Reflectance Spectroscopy.     

Interfacial structure in vulcanized EPDM filled with mercaptosilane-treated Al(OH)3 and its influence on the mechanical properties

The reactivity of the alkoxy group in a silane coupling agent toward inorganic surfaces was investigated, and the structure of a silane-treated layer on the particle surface was analyzed. For this purpose, the various inorganic filler particles, SiO₂, Al(OH)₃, Mg(OH)₂, Al₂O₃, and CaCO₃ were treated with γ-mercaptopropyltrimethoxysilane. A strong interaction between the particle surface and the silane due to the hydrogen bonding and ionic interaction was confirmed except for CaCO₃ by electron spectroscopy for chemical analysis (ESCA). The structure of the silane layer on the particle surface was affected significantly by both the amount of added silane and the treatment conditions. Different silane structures, such as monolayer- or network-like, were formed on the particle surface. Their influences on the mechanical properties of filled vulcanized rubber were also investigated. The silane-treated filler particles, except CaCO₃, showed ability as a semi-reinforcing filler for vulcanized rubber. However, the structure of the silane-layer on the particle surface hardly affected the mechanical properties.     

The interaction of a cationic silane coupling agent with mica

Carbon analysis was used as a method for measuring the quantity of a cationic vinyl benzyl silane (CVBS) adsorbed onto the surface of mica. The results obtained indicate that CVBS can be applied from aqueous solution over a wide pH range with best treatment in neutral and acidic media. The amount adsorbed depends on the concentration of the treating solution in the lower concentration range while in the higher range, the adsorption is less dependent on concentration. The relationship, silane adsorption vs. time of treatment, shows a steplike dependence. It is suggested that each step corresponds to a monolayer coverage. The data indicate that CVBS on mica is a highly ordered and closely packed multilayer phase with the silane molecules oriented normal to the surface. The multilayer adsorption of silane onto silane in this system may be compared in some respects to polymer crystal growth.     

电子墨水用TiO_2显色颗粒的表面改性及其分散性能的研究

为使电子墨水用TiO2显色颗粒能较好地悬浮在有机介质中,利用超声波处理方法,采用硅烷偶联剂(γ-甲基丙烯酰氧基丙基三甲氧基硅烷)在水体系中对TiO2进行表面改性,得到亲油性的TiO2颗粒。研究了硅烷偶联剂用量、pH、超声波处理时间对TiO2亲油化度的影响。实验结果表明,当m(硅烷偶联剂)∶m(TiO2)=3∶10,pH=6,超声波处理时间为30 min时,改性TiO2的亲油化度达到50.51%。傅立叶变换红外光谱(FTIR)图表明硅烷偶联剂已接枝到TiO2颗粒表面。改性TiO2在乙醇中静置24 h只有40%发生沉降,之后基本保持稳定,而未经改性的TiO2仅8 h就几乎完全沉降。经表面改性后TiO2颗粒在乙醇溶剂中的Zeta电位提高到-36.90mV。索氏抽提后,改性TiO2的亲油化度仍能达到47%,TiO2和硅烷偶联剂之间结合力较强。     

An Insight into the Silanization of Montmorillonite Nanoparticles

The purpose of this study is to investigate the effect of reaction conditions on the silanization of montmorillonite nanoparticles using methacryloxypropyltrimethoxysilane (γ–MPS) and to establish relationships between the reaction conditions, the grafting percentage, and the silane arrangement on the particles. The silanization reaction was performed in the following conditions: (i) acidic ethanol-water solution with a pH of 5 and (ii) basic cyclohexane with a pH of 9. To characterize the surface of montmorillonite nanoparticles, analytical methods such as Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), CHN elemental analysis, and X-ray diffraction (XRD) diffraction were utilized. In addition, the dispersion stability of modified particles suspended in different solvents was investigated using a separation analyzer. The results revealed silane grafting in cyclohexane (pH?=?9) achieved higher silanization efficiency, leading to a larger basal spacing in montmorillonite nanoparticles. A parallel arrangement was also suggested for the silane molecules on the surface of the nanoparticles. The higher hydrophobicity of the modified nanoparticles and the decreased overall density of the grafted particles led to a better dispersion in ethanol and toluene.     

Comparative Study of Corrosion Protection of Sol–Gel Coatings with Different Organic Functionality on Al-2024 substrate

In this paper we have studied the effect of addition of amino silane and sulfur silane by 2 wt% into a reference coating solution by using two basic silane coupling agents methyl-tri-ethoxy silane (MTEO) and glycidoxy-propyl-tri-ethoxy silane (GPTS) in 1:1 molar ratio by sol–gel technique. The change in hydrophobicity due to the addition of amino group and thiol group was investigated by contact angle study and sol–gel kinetics was studied by Fourier transform infrared spectroscopy. The thermal resistance and surface morphology was analyzed by thermo gravimetric method and scanning electron microscope. The anti corrosion property of all three coatings were evaluated by potentiodynamic polarization study, AC impedance and salt spray method. X-ray photoelectron spectroscopic method was used to monitor the bonding mechanism of coating matrix with the metal surface. All type of investigations revealed that, addition of thiol group containing silane coating to the reference coating solution has caused remarkable improvement in hydrophobicity and corrosion resistance properties where as amine group rendred the surface less hydrophobic and showed no sign of improvement in corrosion protection. The most probable reason behind this improved performance is due to the additional hydrophobicity imparted by much less polar thiol group. But amino silane provided comparatively poor performance due to the presence of polar amine group.     

冰箱冰柜蒸发器用铝管的硅烷钝化研究

以烯烃酰氧-烷氧基硅烷(MS)为主要成膜剂对冰箱、冰柜蒸发器用铝管进行钝化研究。通过正交实验得到硅烷钝化的最优配方为:MS 50 mL/L,十二烷基磷酸酯5 g/L,乙醇60 mL/L,无机添加剂A 1 g/L,pH值2.0。采用硫酸铜点滴实验、碱浸失重实验和铜盐加速乙酸盐雾实验对所得硅烷膜的耐蚀性进行测定。结果表明:硅烷膜的存在明显提高了铝管的耐蚀性能,耐蚀效果超过了常规的铬酸盐钝化膜。电化学Tafel极化曲线和交流阻抗谱(EIS)的测试表明:硅烷膜的存在使铝的自腐蚀电位明显正移,自腐蚀电流密度显著降低,阻抗值明显增大,从而有效地降低了铝管的腐蚀速率。金相显微镜和原子力显微镜(AFM)对硅烷膜表面形貌测定表明:硅烷膜层主要由大量无定型的固体微粒沉积而成,膜层表面极其致密、均匀和平整,能够在铝管表面起到耐蚀作用。     

Mechanical properties of silane‐treated,silica‐particle‐filled polyisoprene rubber composites: Effects of the loading amount and alkoxy group numbers of a silane coupling agent containing mercapto groups

The surface treatment of spherical silica particles with a silane coupling agent with mercapto groups was carried out. The treated silica particles were incorporated within polyisoprene and then vulcanized. The effects of the loading amount and alkoxy group number of silane on the stress–strain curve of the filled composite were investigated. For this purpose, silanes with dialkoxy and trialkoxy structures were used. The loading amount of silane on the silica surface was varied from 1 to 8 times the amount required for monolayer coverage. The stress at the same strain increased with the silane treatment, and it was higher in the dialkoxy structure than in the trialkoxy structure above 300% strain. There was no significant influence of the loading amount on the stress for the trialkoxy silane structure. However, the stress was influenced by the loading amount, and the maximum stress was observed at 4 times the silane amount required for monolayer coverage for the dialkoxy structure. The stress had a good relationship with the crosslinking density of silica‐filled polyisoprene rubber (measured with a swelling test). The reinforcement effect by the silane treatment of silica was found to be affected strongly both by the entanglement of the silane chain and polyisoprene rubber matrix and by the crosslinking reaction between the mercapto group of silane and polyisoprene rubber in the interfacial region. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of functional groups (methyl,phenyl) on organic–inorganic hybrid sol–gel silica coatings on surface modified SS 316

Organic–inorganic hybrid sol–gel based silica coatings derived from hydrolysis and condensation of organically modified silane precursors like phenyltrimethoxysilane and methyltriethoxysilane along with tetraethoxysilane were deposited on different surface pre-treated (as-cleaned, plasma-treated, shot-blasted) SS 316 grade stainless steel substrate, using dip coating technique. The coatings were heat treated at 150 °C for 2 h in air. The pre-treated surfaces were characterized using X-ray Photoelectron Spectroscopy and Scanning Electron Microscopy. The water content of the sols was determined by Karl Fischer titration to evaluate the degree of completion of hydrolysis and condensation reactions. Cured coatings were characterized to evaluate thickness, water contact angle, pencil scratch hardness, gloss, and shrinkage in coating thickness. Impact test was carried out on pigmented coatings derived from sols synthesized using the two silane precursors. The corrosion resistance and water durability tests were carried out to compare the coatings derived from using different precursors and different surface pre-treatments. The corrosion tests were carried out for 1 h and 24 h exposure to a 3.5% NaCl solution by electrochemical polarization measurements. It was found that coatings from methyl substituted organically modified alkoxysilane exhibited better hydrophobicity, scratch hardness, impact resistance and barrier properties with respect to corrosion, when compared to those derived from phenyl substituted trialkoxysilane. The difference in performance of coatings was explained on the basis of difference in hydrolysis and condensation rates between the two organically modified silane precursors used for the sol synthesis.     

Properties of organic–inorganic composite materials prepared from acrylic resin emulsions and colloidal silicas

To design an organic–inorganic composite material with colloidal silica as the inorganic component, an acrylic resin emulsion and an organic silane hybridized acrylic resin emulsion were prepared by emulsion polymerization. The organic–inorganic composite films were prepared by blending the emulsion and the colloidal silica. The contact angles for water, gloss at 60°, and the transparencies of those films were measured. The dispersion state of colloidal silica in films was observed with a scanning electron microscope (SEM) and a transmission electron microscope (TEM). From these results, the contact angle for water of the organic–inorganic composite film obtained from the silane hybridized acrylic resin emulsion was lower than that of the organic–inorganic composite film obtained from an acrylic resin emulsion. The contact angles for water in organic–inorganic composite films with colloidal silicas were lower than those of the films without the colloidal silicas. The films prepared from silane hybridized acrylic resin emulsion composites with colloidal silicas of less than 100 nm were more hydrophilic. SEM and TEM observations demonstrated that some aggregations of the small colloidal particle silica were densely dispersed on the film surface. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2051–2056, 2006     

Insights on Ceramics as Dental Materials. Part II: Chemical Surface Treatments

The purpose of surface treatment (conditioning) methods on dental ceramics is to improve the retention and bonding between the enamel or the dentin and ceramic veneer, with the help of resin composite luting cements. These types of surface treatments include chemically altering the surface of ceramics with some specific acidic etchants followed by applying a silane coupling agent (silane). The silane currently used in dentistry is 3-methacryloxypropyltrimethoxysilane, a hybrid organic–inorganic trialkoxy ester monomer, which is diluted in an acidified water-ethanol solvent system. Such silane primers are said to be pre-hydrolyzed. Some oxide ceramics with high crystalline content, such as alumina and zirconia, cannot be easily etched with acid etchants. They should be silica-coated and silanized prior to bonding. A silane coupling agent should be applied after silica-coating to the ceramic surface to achieve chemical bonding and the optimal durable bond strength.     

Role of silane grafting in the development of a superhydrophobic clay-alumina composite membrane for separation of water in oil emulsion

Hydrophobic composite kaolin-coated clay-alumina membranes are unique choices for water in oil emulsion separation. In this work, a membrane fabrication approach is presented using kaolin clay coating in the clay-alumina tubular composite support tube and subsequently grafting by different concentrations of fluoroalkyl silane (FAS: 1H, 1H, 2H, 2H, -Perfluorooctyltriethoxysilane) on the membrane surface. Different concentrations of fluoroalkyl silane formed distinctive hierarchical structures which exhibited hydrophobicity of the membrane surface. The pore property, surface roughness properties, and thermogravimetric properties can be suitably tailored by tuning the silane concentration in the grafting solution. The surfaces of comparatively higher silane content grafted (M50 and M100) composite membranes were found to be superhydrophobic. Comparably, our optimal composite membrane (M100) displayed a moderate steady flux rate of 80-100LMH (Lm^?2h ^?1) and excellent water rejection (>99%) properties during the separation of water in hexane and toluene emulsion at a cross-flow transmembrane pressure of 1 bar. The role of silane concentration on permeated hexane and toluene flux rate, water rejection rate, surface wettability, microstructure, and hydrophobic stability reveals new distinguishing insights into the hydrophobic clay-alumina composite membrane fabrication.     

镀锌钢板无机硅烷复合钝化的研究

制备了一种含钛、磷、钒的无机混合液,并掺入到硅烷液中,研究其在镀锌钢板表面的钝化行为.通过CUSO4点滴实验、极化曲线法及扫描电子显微镜测试钝化膜的耐蚀性能及表面形貌.结果表明:镀锌钢板的表面经无机-硅烷钝化后,其耐蚀性明显优于单一硅烷钝化膜的.     

Preparation and corrosion protective properties of nanostructured titania-containing hybrid sol–gel coatings on AA2024

Titania-containing organic–inorganic hybrid sol–gel films have been developed as an alternative to chromate-based coatings for surface pretreatment of aluminium alloys. Stable hybrid sols were prepared by hydrolysis of 3-glycidoxypropyltrimethoxysilane and different titanium organic compounds in 2-propanol solution in the presence of small amounts of acidified water. Different diketones were used as complexing agents in this synthesis for controllable hydrolysis of titanium organics. The properties of the obtained coatings were compared with those of zirconia-containing films. Electrochemical impedance spectroscopy (EIS) measurements and standard salt spray tests were performed to investigate the corrosion protection performance of the hybrid coatings. It was revealed that their protective properties depend significantly on the nature of metalorganic precursors and complexing agents used in the process of sol preparation. The best anticorrosive protection of AA2024 in chloride solutions is provided by the titania-containing sol–gel films prepared with titanium(IV) tetrapropoxide and acetylacetone as starting materials. In the case of zirconia-containing films, better protective properties were found when applying ethylacetoacetate as a complexing agent.     

Influence of silane-based treatment on adherence and wet durability of fusion bonded epoxy/steel joints

Three layers polyolefin coatings are widely used in Europe to protect pipelines against corrosion. Loss of adhesion at a fusion bonded epoxy (FBE)/steel interface has occasionally been observed even on pipelines without external defects. Silane-based surface pre-treatments are developed to improve adhesion with limited impact on the environment unlike usual chromate conversion pre-treatments; however the mechanisms involved in silane action need to be more deeply understood. The application process of silane surface treatment implies a series of key parameters of which optimization is imperative to form a silane layer with good properties at the interface. This paper studies the influence of the cure temperature and the pH of an aminosilane based pre-treatment on adhesion strength and durability via single lap shear tests. SEM/EDX, FT-IR and XPS analyses are used to characterize the silane and silane/epoxy structures. Silane pretreatment improved the FBE joints durability and appears as a relevant solution to replace the usual chromate conversion pretreatments. The joints pretreated at pH 10.6 had better durability than at pH 4.6. This was related to the formation of a bridge across the silane/epoxy interface at pH 10.6, whereas, at pH 4.6, formic acid reacts with amino groups of silanes, limiting the reaction between amino groups and epoxy.     

铝合金表面GPTMS硅烷膜的制备及耐蚀性能研究

为提高铝合金耐腐蚀力,运用正交试验法研究在铝合金表面制备 γ-（2,3-环氧丙氧）丙基三甲氧基硅烷（GPTMS）自组装膜最佳工艺条件,利用极化曲线和扫描电子显微镜研究该硅烷膜在铝合金表面的耐腐蚀性能。研究表明：最佳工艺条件为 100 mL溶液中, pH＝4. 5,V（GPTMS）∶V（EtOH）∶V（H₂O）= 2∶7∶91,T_{1（水解温度）}＝25 ℃,t_{1（水解时间）}＝7 h,t_{2（浸涂时间）}＝10 min,t_{3（固化时间）}＝90 min,T_{2（固化温度）}＝120 ℃,该工艺条件下制备的硅烷膜具有优异的耐腐蚀性能。     

Silane sol–gel film as pretreatment for improvement of barrier properties and filiform corrosion resistance of 6016 aluminium alloy covered by cataphoretic coating

The aim of this study is to develop a newly silane sol–gel pretreatment on the barrier properties and filiform corrosion resistance of 6016 aluminium alloy covered by cataphoretic coating. The sol–gel coatings are used as coupling agent between aluminium substrate and cataphoretic paint. The pretreatment is an aqueous solution of three different silane compounds (glycidyloxypropyltrimethoxysilane (GPS), tetraethoxysilane (TEOS) and methyltriethoxysilane (MTES)) hydrolysed at two different pH (2 and 3.5). A system without pretreatment was studied as reference. The electrocoatings were cured between 155 °C and 195 °C in order to modify their mechanical properties.Polarisation curves, EIS and FT-IR measurements were used in order to characterize the silane layers. EIS measurements were used to follow the barrier properties and the water uptake evolution on intact coatings.The filiform corrosion protection of the coating was also evaluated by a normalized filiform corrosion test.