Use Of Silane Coupling Agents Research Articles

The use of UNIFAC for the estimation of adhesion enhancement between polymers and mineral surfaces treated with silane coupling agents

The group contribution method of UNIFAC is used to investigate the influence on adhesion of thermodynamic compatibility between the filler surface and the polymeric matrix in filled polymeric composites. Compatibility is enhanced between polymers and mineral surfaces through the use of silane coupling agents of varying chemistry. In this study, glass beads were treated with ten different organofunctional silanes intended to induce differences in interfacial strength. Interfacial strength measurements were obtained from tests in which single, silane-treated glass beads were embedded in rectangular poly(vinyl butyral) specimens subjected to uni-axial stress until interfacial failure occurred at one of the poles of the sphere. The UNIFAC method was used to estimate the Gibbs free energies of mixing using the chemical structure of the polymer repeat unit and each of the silane organofunctional groups, and these values were correlated with the measured interfacial strengths. The results indicate that enhanced interfacial strength corresponds to systems with more favorable thermodynamic mixing.

New polymer mortars containing polymeric wastes. Part 1. Microstructure and mechanical properties

Recycling industrial wastes as filler components and/or aggregates in polymer mortars makes these materials very interesting from an ecological and safety point of view. In addition, the resulting materials have useful physical and mechanical properties. Four recycled fillers (powdered rubbers, tyre rubbers, micronized tyre fibers and milled electrical cable wastes) have been used to formulate new polymer mortars. The comparison of their mechanical properties and microstructures with those of a plain polymer mortar indicates that the presence of recycled waste affects the physical–mechanical behavior (compressive and flexural strengths, microstructure). The use of silane coupling agents has been also considered and its effect in leading to more compact materials is reported and discussed.

Atomic Force Microscopy of Elastomers: Morphology, Distribution of Filler Particles, and Adhesion Using Chemically Modified Tips

Abstract The microdispersion of silica and carbon black-based filler particles in unvulcanized and vulcanized ethylene-propylene-diene terpolymer (EPDM) rubbers was investigated by atomic force microscopy (AFM). Tapping mode phase imaging was found to be particularly useful for imaging of the filler aggregates and for the visualization of single primary filler particles. It was demonstrated that the use of silane coupling agents significantly improves the microdispersion of silica filler in the rubber matrix, as compared to (a) silica without coupling agent, and (b) to carbon black. These results correlate very well with the observed mechanical properties of the materials. In addition, adhesion imaging and the analysis of measured pull-off forces allowed us to differentiate between the filler particles and the rubber matrix, as well as between different types of filler particles. The application of chemically modified AFM tips in pull-off force measurements allowed us to monitor the increase of the hydrophilicity as a result of plasma treatment of the surface of crosslinked poly(dimethylsiloxane), and as a result of chlorination of butyl rubber.

Use of silane coupling agents to enhance the performance of adhesively bonded alumina to resin hybrid composites

Silane coupling agents were employed to improve the adhesion of vinyl-ester to alumina (Al 2O 3). Shear test by compression loading (ASTM D905) was used to study dry and wet adhesion. Scanning electron microscopy (SEM) was used to study the uniformity of silane coatings and the fracture modes after shear testing. Results showed that the adhesion and durability of the sandwiched alumina/vinyl-ester systems were significantly improved by certain silane surface treatment for most of the systems.

Polypropylene-wood fiber composites: Effect of treatment and mixing conditions on mechanical properties

Polypropylene/wood fiber composites were prepared at three different temperatures: 170°C, 180°C, and 190°C. The surface of wood fibers was modified through the use of silane coupling agents and/or coating with polypropylene or maleated polypropylene. The fiber coating was performed by propylene polymerization in the presence of wood fibers or by immersion in an o-dichlorobenzene polypropylene (or maleated polypropylene) solution. Tensile and three-point bending tests were performed in order to evaluate the adhesion between matrix and wood fibers. Evidence shows that 180°C is the best mixing temperature, while the use of vinyl-tris (2-methoxy ethoxy) silane with or without maleated polypropylene coating is the best surface treatment. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:1227–1235, 1997

Characterization of experimental composite biomaterials

A comparison was made among the elastic moduli of various combinations of dimethacrylates that may be used as matrix resins in dental restorative composite biomaterials systems. Two ceramic filler materials with contrasting shape and size were synthesized by wet chemistry; these were used to produce a range of experimental composite systems. Dynamic elastic moduli determinations were used to study the influence of filler volume, filler size/shape, use of silane coupling agents, and storage in water. The filler was varied from 0 to 59% by volume for filler A and from 0 to 48% volume for filler B. Silane treatment was found to have a significant effect on modulus. Moduli for composite materials containing silane-treated filler were higher compared to materials containing the same volume loading of non-silane-treated filler. Using a light curing resin as a matrix gave a significantly higher modulus for a filler loading of 38% by volume. Storage in water for 29 days was found to have only a slight effect on moduli for composite systems containing in excess of 20% by volume of filler. The experimental composite systems produced slightly higher values for moduli than were predicted by the theoretical Reuse constant stress model.

Effects of silane coupling agents on internal reinforcement of wood by E-glass and basalt fibers

The internal reinforcement of Douglas-fir by glass or basalt fibers impregnated with resorcinol-phenol-formaldehyde or polymeric diphenylmethanediisocyanate bonding resins has been investigated. The objective was to evaluate the improvement in composite properties by the use of silane coupling agents. Fibers were treated with 3-(4-methoxyphenyl) propyl methyldichlorosilane for use with the phenolic resin, and with 3-aminopropyl triethoxysilane for use with the isocyanate resin. Resin impregnated fiber plies were sandwiched between wood pieces to prepare test specimens with 17 vol. % fiber for measurement of block shear strength, and modulus of rupture (MOR) and modulus of elasticity (MOE) in 3-point bending, and interlaminar shear strength in 5-point bending. The durability under wet conditions was evaluated by subjecting the specimens to an accelerated exposure test (ASTM D2559). It was found that silane application resulted in slight shear strength improvement under dry conditions but much higher increa...

Surface Modification Method of Magnetite Particles by use of Silane Coupling Agents Having Fluorocarbon Chain.

Surface modification method of fine magnetite particles by use of silane coupling agents having fluorocarbon chain was investigated. The magnetic fluid (1, 1, 2-trichloro-1, 2, 2trifluoroethane base) was prepared preliminarily by using oleic acid as a surfactant, and then allowed to react with the silane coupling agent. The amount of oleic acid removed from the magnetite surface during the reaction with the coupling agent was measured by the alkaline titration in methanol, and the high exchange rate (>99%) was observed. The modified fine magnetite particles with silane coupling agent could be well dispersed in poly (chlorotrifluoroethene) and produced the fluoro-oil based magnetic fluid.

Biologically Derived Nanometer-Scale Patterning on Chemically Modified Silicon Surfaces

ABSTRACTIn recent experiments we have patterned smooth HOPG surfaces with periodic arrays of nanometer dimension holes on a 20nm lattice using two-dimensional (2-D) protein crystals as templates. The bacterial cell wall crystals were deposited on HOPG substrate and overcoated at oblique incidence with an ultrathin (3.5 nmn) TiO2 film. Fast atom beam (FAB) milling patterns the TiO2 film into a screen having the protein lattice periodicity and the screen then acts as a mask for the pattern transfer to the HOPG substrate. This method provides an inexpensive, “benchtop,” intrinsically parallel technique for the periodic nanostructuring of surfaces. Here we extend it to the patterning of silicon single crystal surfaces. We will describe the use of silane coupling agents to enable protein adhesion with the cytoplasmic side up, as is preferable for the patterning. We will show AFM images of the T1O2 -protein-silicon composite surface at various stages of the fabrication process.

Kinetics and mechanism of the hydrolysis and alcoholysis of alkoxysilanes

As part of our work with the use of silane coupling agents, we have been investigating the transformations of alkoxysilancs into siloxanes. The influence of a para-substituted phenyl group attached to the silicon was investigated and the rates of acid catalyzed hydrolysis and alcoholysis of these para-substituted phenylalkoxysilanes have been determined. The kinetics and mechanism of the reactions are presented. These reactions are of interest because of their role in the use of silane coupling agents as adhesion promoters, in the preparation of zinc-rich silicate coatings, in the sol-gel process and in the preparation of silicones in general. The hydrolysis reaction was found to be first order in acid, zero order in water and to have a Hammett p of -1.42 when catalyzed by sulfuric acid. These results are consistent with current opinion that the reaction mechanism is SN1, and involves a positive intermediate, possibly a siliconium intermediate. The alcoholysis reaction was found to be first order in both ...

Methods for improving the performance of silane coupling agents

The use of silane coupling agents in mineral- and glass-reinforced composites is well known. They impart improved initial mechanical properties, but, more importantly, they cause mechanical properties to be retained during the use of the composite. The main cause of loss of mechanical properties is attack of water at the interface. Recent research has focused on imparting more durable bonding of the silane coupling agent to both the polymer and the reinforcement. Improved silane coupling agent systems have been developed by utilizing several techniques: blends of hydrophobic silanes with hydrophilic silanes to give greater hydrophobic character; use of 1,2-bis-(trimethoxysilyl)ethane as an additive to give increased siloxane crosslinking; use of more thermally stable silanes such as phenyltrimethoxysilane and N-[2-(vinylbenzylamino)-ethyl]-3-aminopropyltrimethoxysilane to give increased thermal stability; and the use of a carboxy-functional silane with a carboxy-functional polymer and zinc salt to give io...

The use of silane coupling agents in ceramic injection moulding

Ceramic injection-moulding blends containing 56 vol % fine silicon nitride and 65 vol % coarse silicon powder in a polypropylene and wax vehicle were prepared by dispersive mixing with and without 2 p.p.h. silane coupling agent based on the weight of powder. The addition of silane reduced the viscosity and the pseudoplasticity of the suspensions considerably. The mechanical strength of the moulding compositions, which may influence the tendency to crack during solidification in the cavity, was marginally increased. The treated silicon powder was strongly hydrophobic but this was not the case with the silicon nitride powder.[/p]

Retention of antioxidants in polyethylene by silane coupling agents

AbstractAntioxidant additives in polyethylene films have been shown to diffuse to the surface where they are subsequently lost, exposing the polymer to oxidation. Compatibility of antioxidants with polyethylene may be increased by use of silane coupling agents. In this study, three approaches to antioxidant modification are examined: (1) bonding antioxidant directly to silicon, (2) coupling the silane to an antioxidant hydroxyl function, and (3) dissolving antioxidants in silanes. All three approaches are shown to be effective in reducing antioxidant loss by diffusion.