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.     

Hydrolysis and condensation of silanes in aqueous solutions

Aminosilanes hydrolyze rapidly in aqueous acidic solutions and exhibit good stability; however ¹H NMR measurements indicate that γ-MPS (γ-methacryloxypropyltrimethoxy silane) hydrolyzes slowly and condenses rapidly under similar conditions. The rate constant of these two reactions depends upon the pH of the solution, and the rate constant of the condensation reaction also depends upon the initial γ-MPS concentration. The hydrolysis is faster and the condensation slower at low pH's. These factors explain why an induction period is observed before the adsorption of γ-MPS onto mica takes place and why it does not occur if the induction period is too long. Using the Lentz technique, it is also shown that the main species resulting from the condensation of a concentrated γ-MPS solution is a cyclic trimer or tetramer, in agreement with literature results.     

Effect of mica surface treatment on mechanical properties of mica-flake-reinforced cement composites

To determine how the surface modification of mica influences flexural strength and fracture toughness of mica-reinforced cement composites, mica was treated with HF acid and three coupling agents: two silanes (CVBS, γMPS) and a titanate (IDT). Significant increases in mechanical properties resulted, depending on type of treatment, concentration of treating solution, reaction time, and w/c ratio.     

Coupling of polystyrene to a silane-treated mica

This paper deals with the coupling of polystyrene to a closely packed and highly ordered cationic vinylbenzyl silane (CVBS) on mica. It is shown that a thermal treatment is required for maximum retention of polystyrene on treated mica. Moreover, a thermal treatment at 250°C is much more effective than one at 170°C. The effect of the number of silane monolayers on mica was investigated. In general, one monolayer of CVBS gave optimum retention of polystyrene. The addition of peroxides further improved this retention and at the same time allowed the use of lower treatment temperatures. Some data are presented which consider the importance of the silane solution concentration and silane functional groups.     

The role of additional silane coupling agent treatment in oxygen plasma-treated UHMPE fiber/vinylester composites

Ultra-high modulus polyethylene (UHMPE) fiber was treated with oxygen plasma and a silane coupling agent in order to improve the interfacial adhesion between the UHMPE fiber and vinylester resin. The oxygen plasma and γ-methylmethacryloxypropyltrimethoxysilane (γ-MPS)-treated UHMPE fiber/vinylester composites showed a slightly higher interlaminar shear strength than the oxygen plasma-treated UHMPE fiber/vinylester composites. The interfacial adhesion of the oxygen plasma-treated UHMPE fiber/vinylester composites in this study is mainly due to mechanical interlocking between the micropits formed by the oxygen plasma treatment and the vinylester resin. The γ-MPS molecules adsorbed onto the UHMPE fiber surface neither affected the morphology of the UHMPE fiber surface, nor reduced the extent of mechanical interlocking. The improved interfacial adhesion by the γ-MPS treatment is due to enhanced wettability and chemical interaction through the chemically adsorbed γ-MPS molecules, as detected by Fourier-transform infrared (FT-IR) spectroscopy. The γ-MPS molecules adsorbed onto the ultra-high molecular weight polyethylene (UHMWPE) plate surface also reduced the aging effect of the oxygen plasma-treated UHMWPE surface.     

Performance improvement of glass-fiber-reinforced polystyrene composite using a surface modifier. II. Mechanical properties of composites

The mechanical properties of glass-fiber-reinforced polystyrene composites were investigated with the variation of glass fiber content, surface treatment conditions, and silane coupling agents. γ-MPS, GPS, and poly(γ-MPS-co-stvrene) were used for the surface modification of glass fiber. Mechanical properties of glass-fiber-reinforced polystyrene composites increased with increasing the content of glass fiber. Poly(γ-MPS-co-styrene) was superior to γ-MPS and GPS in promoting the interfacial adhesion of glass fiber-reinforced polystyrene composites. The mechanical properties of composites were maximum at a low copolymer concentration when the γ-MPS content in the copolymer was high and vice versa. © 1996 John Wiley & Sons, Inc.     

Studies of the simulation of silane coupling agent structures on particulate fillers; the pH effect

The molecular structure of γ-methacryloxypropyltrimethoxysilane (γ-MPS) deposited on the surfaces of particulate mineral fillers was modeled by adjusting the pH of an aqueous alcoholic solution of the silane in absence of a substrate. Hydrolyzates obtained from the solution were studied by gel permeation chromatography (GPC) and Fourier transform infrared spectroscopy (FT-IR) and found to be polymethacryloxypropylsilsesquioxanes whose configuration and molecular-weight distribution were dependent on the solution pH. In acidic environments (below pH 4) the polycondensation mechanism appeared to proceed in a selective manner to form polycyclic blocks which resemble a beaded chain following condensation between blocks. Under more neutral and basic conditions (at or above pH 4) the polycondensation mechanism, resulted in polymethacryloxypropylsilsesquioxanes with the more equilibrated double chain ladder configuration. The molecular weight distribution of these structures was dependent on the stability of the silanol or the silanolate ion. Extremely high-molecular-weight and polydisperse polymethacryloxypropylsilsesquioxanes were generated at near neutral pH due to the formation of the double chain ladder configuration and the high silanol instability in this pH range. The two different polymethacryloxypropylsilsesquioxane configurations were also observed on γ-MPS modified metal oxide substrates. The structures help explain some of the previously observed trends with respect to γ-MPS adsorption on particulate mineral fillers. In strongly basic environments the methacrylate function of γ-MPS partially hydrolyzes to form sodium carboxylate, and carbon dioxide is absorbed from the air and reacts to form sodium carbonate.     

Rheological properties of fumed silica filled Bis-GMA dispersions

The rheological properties of Bis-GMA dispersions filled with fumed silica were investigated to optimize the manufacturing process and mechanical properties by using a Rheometrics Mechanical Spectrometer (RMS). Steady and dynamic measurements on the RMS were carried out to obtain shear viscosity and dynamic mechanical properties. The effect of several factors on the rheological properties of fumed silica dispersions was also examined. The factors were a concentration of a silane coupling agent (γ-MPS), the methods of surface treatment of fillers, silica content, diluent concentration, shear rate, and operating temperatur. From these studies, it was observed that shear viscosity showed an asymptotic phenomenon at a higher concentration than a uniform multi-layer coverage concentration of γ-MPS. The silane coupling agent had a significant role in the reduction of tan δ, resulting from a decrease of loss modulus, while fillers decreased tan δ by increasing the storage modulus. In cases where the silica content and diluent concentration increased simultaneously, the Barcol hardness of Bis-GMA/silica composites was increased, but there was no change in the viscosity of dispersions and diametral tensile strength of those composites.     

Curing of unsaturated polyester resins: Effect of surface treatment of particulates

The effect of surface treatment of particulates on the curing kinetics of unsaturated polyester resin has been investigated using a differential scanning calorimeter. Two coupling agents, γ-methacryloxy propyltrimethoxy silane (γ-MPS) and phenyltriethoxy silane (PTS), were employed. The former reacted with the resin; the latter did not. A kinetic model of free radical addition polymerization was used. A correction factor was used to represent the effective free radical concentration in order to account for the formation of charge transfer complex between the glass beads and the free radicals in the resin. The results indicate that (1) the resin with treated particulates showed generally faster reaction rate and conversion than the resin with untreated particulates; (2) no obvious difference on the curing kinetics was observed between these two coupling agents; the primary role of coupling agent is to inhibit the influence of particulates on the curing kinetics of the resin by effective surface coverage; and (3) a minimum aqueous concentration of 0.05 wt% was suggested for surface treatment of particulates; the reaction rate of the resin was slightly improved when the concentration of the coupling agent was 0.01 wt%; this might possibly be due to insufficient coverage of the particulate surface.     

Adhesion promotion of the polyimide–copper interface using silane-modified polyvinylimidazoles

In order to promote the interfacial adhesion strength between polyimide (PI) and copper, the copper surface was treated with polyvinylimidazole (PVI) or silane-modified PVIs. They were prepared by the copolymerization of 1-vinylimidazole (VI) with the following silane coupling agents: 3-(N-styrylmethyl-2-amino-ethylamino)propyltrimethoxysilane (STS), vinyltrimethoxy silane (VTS), allyltrimethoxy silane (ATS), and γ-methacryloxypropyltrimethoxysilane (γ-MPS). The mole ratio of the silane coupling agent to VI was fixed at 1 : 1. The lap shear strengths between PI and copper were measured at the following different bonding temperatures: 290, 320, 350, and 380°C. In each case, the maximum adhesion strength was obtained at 350°C. VTS-modified PVI showed the best performance on adhesion promotion of the PI–copper interface. Fourier transform infrared spectroscopy was applied to investigate the thermo-oxidative degradation of PI and oxidation of copper. In addition, scanning electron microscopic analysis and contact angle measurements were performed for the investigation of the interaction between PI and silane-modified PVIs. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1343–1351, 1998     

The interaction of alkoxy silane coupling agents with silica surfaces

The interactions of γ-aminopropyltriethoxy silane (A-1100), γ-methacryloxytrimethoxy silane (A-174), γ-glycidoxytrimethoxy silane (A-187), and ethyltriethoxy silane (A-15) with silica surfaces have been studied by means of infrared spectroscopy. The results indicate that the major force holding the silane to the silica surface after application from dilute solutions is primary chemical bonding. These bonds are formed by a condensation reaction between silanols on the hydrolyzed form of the silane and hydroxyl groups on the silica surface. In the case of the amino-silane (A-1100), hydrogen bonding was found to exist but was of minor importance in bonding the silane to the surface. In studying the effects of the addition of water, acetic acid, or n-propylamine to various silane treating solutions, it was found that n-propylamine has a unique catalytic effect on the condensation reaction. This catalytic effect explains the observation that γ-aminopropyltriethoxy silane is more reactive than the other silanes studied. It is felt that silanes not containing an amine group can be made more effective if they are applied in the presence of an amine catalyst.     

Sorption of tryalkoxysilane in low-cost porous silicates using a supercritical CO2 method

The internal surface of micro and nanoporous substrates can be modified in terms of charge, functionality or even reactivity or stability by means of bifunctional organic molecules able to self-assembly. This work investigates the impregnation with trialkoxysilanes of porous systems using supercritical carbon dioxide (scCO₂) as a solvent, which combines several advantages such as liquid-like density and high solvating power with gas-like transport properties. Moreover, scCO₂ does not have specific interactions with the substrate and there is no competition for absorption between added reagents and solvent molecules. The work aims at describing a generic liquid-solventless impregnation method applicable to macro (perlite), meso (silica gels and agglomerated nanoparticles) and microporous (zeolite) silica-based substrates using scCO₂. The hydrophobic octyltriethoxysilane was used to impregnate the internal surface of the chosen substrates with the objective of obtaining high capacity oil adsorbents. FTIR, TGA and N₂ adsorption isotherms were used to determine the interactions between the substrate and the silane deposited monolayer. The acquired hydrophobic character was evaluated using the Karl Fischer method to measure the loss in water adsorption capacity after silane grafting.     

Hydrolysis,adsorption, and dynamics of silane coupling agents on silica surfaces

The hydrolysis of alkoxysilane coupling agents has been followed using proton NMR. The disappearance of the silane ester and the appearance of the alkoxy group were observed to follow pseudo-first-order kinetics. The apparent rate constant was found to be dependent on the concentration of the silane coupling agent and the pH. The adsorption of the coupling agents onto Cab-O-Sil silica was quantified using FT-IR spectroscopy. It was found that monolayer coverage was obtained with about 0.65 mmol/100 m². Solid-state deuterium NMR was used to probe the behavior of the coupling agent on the silica. The coupling agents adsorbed on the surface from deuterated aminopropyltriethoxysilane (DAPES) and deuterated aminobutyltriethoxysilane (DABES) showed similar motional characteristics. In contrast, the mobility of condensed polymers from DABES was much less restricted than that from DAPES. The amount of hydrolysis in acetone-water mixtures increased the amount of surface-adsorbed material and lessened surface mobility. Overpolymerization with bismaleimide increased the rigidity of the surface layer of the coupling agent.     

硅烷改性聚羧酸减水剂-Na2SO4-水泥体系分散及流变性能的研究

采用γ-甲基丙烯酰氧基丙基三甲氧基硅烷(KH570),丙烯酸(AA)以及甲基烯丙基聚氧乙烯醚(HPEG)单体,通过自由基聚合法合成了硅烷改性聚羧酸减水剂(SPC).试验研究了引入硅烷官能团后,减水剂分子成分、电荷密度以及对Na2SO4-水泥体系分散及流变性能的影响规律.研究结果表明,在SPC红外特征峰中发现了Si-O的伸缩振动峰,说明SPC成功引入硅烷官能团;电荷密度测试表明,PC比SPC具有较高的-COO-含量;通过分散性能、流变性能及吸附量测试,表明与PC相比,SPC能够通过≡Si-OH与水泥颗粒表面的-OH发生化学缩合反应,提高减水剂分子在Na2SO4-水泥体系中对水泥颗粒表面的吸附能力,降低屈服应力和塑性粘度,从而提高减水剂对水泥浆体的分散及流变性能.     

Examination of acid-base properties of alumina treated with silane coupling agents, by using inverse gas chromatography

This study examined the specific component of the free energy of adsorption, − ΔG_A^SP, of the untreated and four types of silane coupling agent-treated alumina powders using inverse gas chromatography (IGC) by employing the adsorption of several polar and non-polar probes onto their surfaces at various temperatures. The acid-base properties of the untreated and surface-treated alumina powders were quantified using their K_A and K_D parameters, which reflect the ability of a surface to act as an electron acceptor and donor, respectively. The surface of the untreated alumina was found to be amphoteric and was able to function as both an electron acceptor and donor. The acid-base properties of the alumina surfaces treated with γ-glycidoxy propyl trimethoxy silane (GMS) and γ-amino propyl triethoxy silane (AES) were slightly basic, and those of the alumina surfaces treated with γ-methacryloxy propyl trimethoxy silane (MTMS) and γ-mercapto propyl trimethoxy silane (MCMS) were amphoteric.     

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。     

The Influence of Interfacial Structure on the Flexural Strength of E-glass Reinforced Polyester

Simultaneous mechanical and molecular characterization of a composite system has been attempted with respect to the interface. The mechanical properties of an E-glass cloth/ y-methacryloxypropyltrimethoxysilane (γ-MPS)/bisphenol-A-fumarate polyester resin composite system were studied as a function of the amount of γ-MPS coupling agent present on the glass fiber surface. Fourier transform infrared diffuse reflectance spectroscopy was used to determine the amount and structure of γ-MPS on the glass. This structure consists of two clearly distinguishable regions: physisorbed layers of γ-MPS which can be dissolved by organic solvents, and chemisorbed layers which are insoluble. The physisorbed layers of γ-MPS reduced the strength of the polyester composite. A polymer blend consisting of siloxane oligomer of γ-MPS and bisphenol-A polyester was also investigated as a model of the silane interphase. Results from this model study are in agreement with the polyester composite data.     

A new organofunctional methoxysilane bilayer system for promoting adhesion of epoxidized rubber to zinc: Part 1: Optimization of practical adhesion

Practical adhesion of rubber to zinc cords is measured for various zinc silanization treatments. Aminopropyltrimethoxysilane (APS) alone or both APS and mercaptopropyltrimethoxysilane (γ-MPS) were used as coupling agents for zinc and epoxidized natural rubber (ENR). It is shown that special chemical and physical conditions are required to provide strong practical adhesion. With APS alone, best results are obtained when the zinc is silanized with 1% APS in isopropanol–water, cured at 110 °C for 1 h in air and vulcanized with ENR (20% epoxy groups) at 170 °C for 15 min. The adherence is further improved by double silanization with γ-MPS (0.5%) and then APS (1%). In both cases, the concentration of silanes, the cure temperature of the silane layers, the ageing and acidity of the silane solutions are the main parameters which must be thoroughly optimized. In the case of double silanization, the highest practical adhesion seems to be correlated with a true γ-MPS/APS bilayer structure which is achieved for a specific application of the γ-MPS. It is suggested that this layer is bound to zinc through its thiol function, and the APS layer (on the γ-MPS layer) is cross-linked to γ-MPS and ENR through silanol and epoxy groups, respectively. When the silanized zinc surface was vulcanized and the rubber then peeled off the zinc surface, XPS analysis of the bare zinc areas indicates a rupture characteristic of an adhesive failure in the case of silanization by APS alone, and a cohesive failure in the case of the double silanization.     

载体孔结构对常温COS水解催化剂性能的影响

运用固定床流动态反应装置和压汞仪等手段考察了γ-Al₂O₃载体的比表面和孔结构对常温COS水解催化剂反应性能的影响。结果表明,载体必须具有适当的比表面积和孔结构,以利于反应物分子在催化剂表面吸附并与活性中心接触,同时也有利于产物分子脱附并离开催化剂表面。     

AFM observations of silane coupling agent layers having a vinyl group deposited on a mica surface

The topography of silane layers deposited on an inorganic surface was observed using atomic force microscopy. For this purpose, cleaved mica plates were treated with some silane coupling agents at various conditions. Silanes having a vinyl group as the organic functional group with mono-, di- and trialkoxy structures were used. Four different solvents for silane solutions, 2-propanol, 2-propanol/water mixture, water and toluene, were used. The pH of the aqueous solution was controlled. As a result, the suitable solvent and pH were identified in order to obtain a smooth silane layer. The solubility of silane in the solution, the wettability of silane onto the inorganic surface and the depression of the self-condensation of silane molecules in the solution were found to be important parameters for this purpose.