Role Of Silane Coupling Agent Research Articles

The Role of Silane Coupling Agents and Universal Primers in Durable Adhesion to Dental Restorative Materials - a Review

One of the most important aspects in the field of dentistry is adhesion. Adhesion can be enhanced through different mechanisms, most commonly by chemical and mechanical modifications of dental material surfaces. One example of chemical adhesion utilizes primers or bonding agents containing coupling agents. Universal primers which are (mainly organophosphate-based monomers) and silane coupling agents are the most effective and most widely used for unifying dissimilar materials. Other than improving adhesion, Silanes have many other applications in dentistry. They have been found also to enhance the mechanical properties of materials either by adhesion or by becoming a constituent of dental materials itself. Universal primers, on the other hand, are utilized in bonding between different dental materials such as ceramics, metals, alloys, as well as to resin composites. Unfortunately, these primers, coupling agents, and bonding agents have, in general, poor hydrolytic stability. They are susceptible to humid oral environment, which invariably render them potentially unstable in the humid oral environment as saliva is always present. Improving their hydrolytic stability should therefore result in stronger adhesion for dental materials and dental prosthesis with a better clinical survival rate.

Rheology, mechanical, and thermal properties of core–shell silicon-acrylic copolymer emulsion films and its application on surface sizing: role of silane coupling agent

With the assistance of polymerisable maleate surfactant and costabilizer, core–shell emulsions with poly(butyl acrylate) core (PBA) and poly(butyl acrylate–styrene–methacryloxypropyl trimethoxysilane) shell (PSBM) were prepared through seeded emulsion polymerization. Effects of MPTS on rheological, mechanical, and thermal properties were investigated. Simultaneously, the emulsions were utilized as paper surface sizing agents, and corresponding properties were studied. It was found that the emulsion possessed viscoelastistic nature and changed from viscous to elastic with MPTS addition. At the same time, enhanced internal network strength among particles was detected, which was weakened when MPTS concentration was 8%. The tensile strength and thermal stability of copolymer films were therefore increased accordingly. However, decrease in tensile strength, elongation at break and thermal properties was observed with higher MPTS concentration due to weakened interaction among different shells. It was also found that glass transition temperature (Tg) did not influence greatly by MPTS, and two phases corresponding to core and shell copolymer were observed with low degree of microphase separation. Furthermore, the interaction between polymer and fiber was improved, resulting in improved sizing degree, ring crush strength, surface strength, and folding strength. While the surface strength and folding endurance decreased due to the increase of brittleness with higher crosslinking degree.

The Effect of Silane Coupling Agents on the Viscoelastic Properties of Rubber Biocomposites

AbstractSummary: This paper deals with the dynamic mechanical study of sisal/oil palm hybrid fiber reinforced natural rubber composites (at frequency 1 Hz) with reference to the role of silane coupling agents. Composites were prepared using sisal and oil palm fibers subjected to chemical modifications with different types of silane coupling agents. The silanes used were Silane F8261 [1,1,2,2‐perfluorooctyl triethoxy silane], Silane A1100 [γ‐aminopropyltriethoxy silane] and Silane A151 [vinyl triethoxy silane]. It was observed that for treated composites, storage modulus and loss modulus increased while the damping property was found to decrease. Maximum E' was exhibited by the composite prepared from fibers treated with silane F8261 and minimum by composites containing fibers treated with silane A151. This was attributed to the reduced moisture absorbing capacity of chemically modified fibers leading to improved wetting. This in turn produced a strong interfacial interface giving rise to a much stiffer composite with higher modulus. Surface characterization of treated and untreated sisal fibers by XPS showed the presence of numerous elements on the surface of the fiber. Scanning electron micrographs of tensile fracture surfaces of treated and untreated composites demonstrated better fiber–matrix bonding for the treated composites.Scheme of interaction of silanes with cellulosic fibers.magnified imageScheme of interaction of silanes with cellulosic fibers.

Kinetics of interaction of hardened oil-well cement slurries with acidic solutions from isothermal heat-conduction calorimetry

The kinetics of interaction of hydrochloric acid with oil-well cement slurries treated with the silane coupling agents, tetraethyl orthosilicate, 3-(trimethoxysilyl)-1-propanethiol and 3-(chloropropyl)-trimethoxysilane have been investigated isothermal heat-conduction calorimetry at 298.15 K. The Avrami kinetic model gives a better fit to the experimental data than the traditional Lagergren kinetics models. A pore diffusion model suggests acid diffusion only for the standard slurry. The results indicate that isothermal heat-conduction calorimetry is suitable to evaluate the protective role of silane coupling agents on hardened oil-well cement slurries.

Role of silane coupling agents for performance improvement of poly(vinyl acetate)/tetraethyl orthosilicate hybrid composites prepared by a sol–gel process

Role of silane coupling agents for performance improvement of poly(vinyl acetate)/tetraethyl orthosilicate hybrid composites prepared by a sol–gel process

Role of silane coupling agents for performance improvement of poly(vinyl acetate)/tetraethyl orthosilicate hybrid composites prepared by a sol–gel process

AbstractSilica based poly(vinyl acetate)/inorganic hybrid composites were prepared via a sol–gel process under acidic conditions. Because the phase behaviour of the hybrids is greatly affected by weak interactions such as hydrogen bonding between organic polymer and inorganic network, two types of silane coupling agent (vinyl trimethoxysilane and 3‐(trimethoxysilyl)propyl methacrylate) were used to introduce specific interactions and to control phase behaviour in the interface between polymer and silica. The interfacial interactions between polymer and inorganic segment in the presence of silane have been investigated by Fourier transform infrared spectroscopy. Thermogravimetric analysis shows that the thermal stability of organic components in the hybrids is enhanced by addition of silane coupling agents. Scanning electron micrographs reveal that silica particles are homogeneously dispersed in the organic matrix as a result of the specific interactions.© 2001 Society of Chemical Industry

Role of silane coupling agent and polymeric film former for tailoring glass fiber sizings from tensile strength measurements

Tensile strengths of differently sized E-glass fibres have been characterised using a bimodal Weibull two parameters cumulative distribution function. By comparing unsized fibres, pure silanes, different film formers, and silane/film former combinations, a comprehensive summary on the healing effect for surface flaws in relation to the type of sizing emulsion has been obtained. The great influence of the film former, which is the main component of the sizing by weight, was shown to affect both the healing of initially occuring flaws in the unsized fibre and the possibility of creating new defects. Besides the single influence of the film former, the synergetic effect of silane and film former polymer has been shown. In fact, the presence of sizing influences both the population of flaws on the fibre surface and the structure of the interphase, which will be created from the impregnation with a polymer matrix. Data from statistics of fracture as a function of the nature of sizings were discussed according to the literature on stress corrosion of E-glass filaments.

The role of a silane coupling agent in the synthesis of hybrid polypyrrole–silica gel conducting particles

The preparation of new hybrid conducting polymer–silica gel particles is described. The silica gel acts as a high surface area substrate (431 m2 g–1) for the in situchemical synthesis of conducting polypyrrole in aqueous solution in order to obtain hybrid polypyrrole–silica particles. The role of a common silane coupling agent (i.e. aminopropyltriethoxysilane, APS) in the pretreatment of silica gel prior to polymerization and preparation of polypyrrole–APS–silica particles is also investigated. It was found by TGA that the polypyrrole mass loading is higher in polypyrrole–APS–silica than in polypyrrole–silica particles. XPS results indicated that APS-treated silica leads to polypyrrole-rich surface particles not found with the untreated silica. Consequently, the polypyrrole–APS–silica pellets were three orders of magnitude more conductive than those of polypyrrole–silica.The surface area of the polypyrrole–silica (422 m2 g–1), as measured by BET, matched that of the untreated silica whilst that of the polypyrrole–APS–silica (162–184 m2 g–1) is significantly lower. The combination of XPS, TGA, BET and conductivity measurements suggest that pyrrole is predominantly polymerized in the pores of the untreated silica gel whilst the APS pretreatment of silica leads to the formation of a thin overlayer of polypyrrole at the surface of the silica gel in addition to a higher conducting polymer loading in the gel pores.

The silane/sizing composite interphase

AbstractSilane coupling agents are but one of many ingredients in commercial sizings that are applied to glass fibers. The chemistry of a silane coupling agent alone allows it to react with both the glass fiber surface and the epoxy matrix to increase the fiber/matrix adhesion. However, the action of a commercial sizing system containing a silane coupling agent along with other components is not well understood. Research has been conducted in which the physical properties have been measured of blends of epoxy‐compatible silane/sizing made with bulk matrix at concentrations representing likely compositions found at the fiber‐matrix interphase as a result of processing and fabrication. It has been shown that the silane/sizing interaction with the epoxy matrix produces a material with vastly different properties than those of the bulk matrix. In this particular system, the model interphase has a lower Tg higher modulus, and greater tensile strength, but lower toughness. The results from the present study show that a themical interaction theory of adhesion alone is not sufficient to explain the role of silane coupling agents in glass fiber‐epoxy matrix adhesion. Consideration must be given to the interphase and its mechanical properties.

Evidence for Chemical Bond Formation at Silane Coupling Agent Interfaces

An investigation of the physical chemical role of silane coupling agents at the glass-resin interface has been conducted. Radio actively labeled coupling agents were synthesized and purified, and their adsorption on E-glass and aerosil surfaces studied. The infor mation obtained from these tracer studies and from electron photo micrographic examination of fiber surfaces indicate that coupling agents form continuous films on E-glass surfaces with covalent bonding occurring at the interface. Failure of the glass-coupling agent interface in the presence of boiling water occurs by attack on the glass substrate itself. Using radioactive tracer techniques, it was also determined that copolymerization can occur at the coupling agent-resin interface.