Role Of Silanes Research Articles

Hematite/M (M = Au, Pd) Catalysts Derived from a Double-Hollow Prussian Blue Microstructure: Simultaneous Catalytic Reduction of o- and p-Nitrophenols.

Present study deals with hematite/M (M = Au, Pd) catalysts converted from a double-hollow Prussian blue microstructure (DHPM). The unique Prussian blue (PB) microstructure (MS) is prepared by a template-free solvothermal synthetic route in a single-step reaction. An amine-functionalized silicate sol-gel matrix (SSG) has served as the structure-directing agent cum stabilizer for making DHPM. Synthesized DHPM is having a unique structure: a hollow core and an in situ etched porous surface. Growth mechanism is explored and revealed by analyzing several experimental parameters such as HCl concentration, Fe source, effect of the added EtOH, silane concentration, and role of silanes' amine groups. It is identified that the superstructure consisted of well-aligned PB cubes growing radially from the core of the superstructure. Metal (Au and Pd) nanoparticles (NPs) are deposited on both interior and exterior of the PB MS through galvanic displacement reaction, and thus metal NP-loaded hematite phase iron oxide (α-Fe2O3) nanomaterials were derived by annealing them in air. Catalytic activities of the hematite/M(M = Au, Pd) MS are investigated toward simultaneous catalytic reduction of o-nitrophenol and p-nitrophenol. The resultant hematite/Pd MS showed high structural stability and catalytic active sites than the hematite/Au MS, which enhances the catalytic properties for the simultaneous catalytic reduction of both nitrophenols.

Micro and nanocomposites of polybutadienebased polyurethane liners with mineral fillers and nanoclay: thermal and mechanical properties

AbstractMicro and nanocomposites of hydroxyl terminated polybutadiene (HTPB)-based polyurethanes (NPU) were obtained using five mineral fillers and Cloisite 20A nanoclay, respectively. Samples were prepared by the reaction of HTPB polyol and toluene diisocyanate (TDI), and the chain was further extended with glyceryl monoricinoleate to produce the final elastomeric polyurethanes. Mechanical and thermal properties were studied, showing that mineral fillers (20%w/w) significantly increased tensile strength, in particular nanoclay (at 5% w/w). When nanoclay-polymer dispersion was modified with a silane and hydantoin-bond promoter, elongation at break was significantly increased with respect to NPU with C20A. Thermal properties measured by differential scanning calorimetry (DSC) were not significantly affected in any case. The molecular structure of prepared micro and nanocomposites was confirmed by Fourier transform infrared (FTIR) spectroscopy and Raman spectroscopy. Interaction of fillers with polymer chains is discussed, considering the role of silanes in compatibilization of hydrophilic mineral fillers and hydrophobic polymer. The functionalization of nanoclay with HMDS silane was confirmed using FTIR. Microstructure of NPU with C20A nanoclay was confirmed by Atomic Force Microscopy (AFM).

Hygrothermal Aging of Silane-Laced Epoxy Coatings

The impact of silane on the hygrothermal stability of epoxy coatings was investigated by specular neutron reflectivity (NR). By comparing the hygrothermal degradation behavior of neat novolac epoxy coating and corresponding bis[3-(triethoxysilyl)propyl]tetrasulfide-laced epoxy coating, the role of silane was elucidated. Accelerated aging was achieved by exposing the samples to 80°C liquid water. For the pure epoxy coating, degradation occurs at the coating–substrate interface, which makes the coating vulnerable to adhesion failure. For epoxy–silane coating the addition of silane imparts resistance to the interfacial degradation observed in the neat epoxy coating.

Mechanistic Investigation of the Silane, Germane, and Stannane Behavior When Incorporated in Type I and Type II Photoinitiators of Polymerization in Aerated Media

The role of silanes, germanes, and stannanes R3XH as co-initiators and additives to overcome the oxygen inhibition usually encountered in photopolymerization reactions in aerated media is demonstrated in experimental conditions where both a low light intensity and thin and low-viscosity samples are used. These results concerned with silanes as co-initiators are compared to data previously obtained in more viscous media where a lower effect of oxygen is expected. The striking role of R3XH here is their use as additives in both type I and II photoinitiating systems. It allows to dramatically increase the polymerization rates and the final monomer conversions in the above-selected conditions. The mechanisms investigated by laser flash photolysis (LFP) and electron spin resonance (ESR) experiments are discussed.

ChemInform Abstract: The Role of Silanes on the Copper‐Catalyzed Conjugate Alkylation of Enones by Organoaluminium Reagents.

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The role of silanes on the copper-catalyzed conjugate alkylation of enones by organoaluminium reagents

The effect of silanes as additives in the copper-catalyzed conjugate alkylation of enones by various organoaluminium reagents was investigated. TMSCl led to significant lower amounts of CuBr catalyst needed in the reaction of trimethylaluminium with enones, but was unsuccessful in the case of organoaluminium compounds of the formula Me 2AlY (Y = Cl, OR). Me 2AlOEt turned out to be a useful reagent for methylation without support of additives.

The role of silane and N 2O in the CO 2 laser-CVD of silicon oxide films

The laser-CVD of silicon oxide films on silicon substrates has been carried out using a CW-CO 2 laser in a parallel configuration, and with SiH 4 and N 2O as precursor gases. In this paper we report the influence of the reactant partial pressures on the film growth rate. The individual apparent orders of the chemical reaction for SiH 4 and N 2O have been determined.

Role of silanes in adhesion. Part II. Dynamic mechanical properties of silane-treated glass fiber/polyester composites

—Glass fiber/unsaturated polyester composites, prepared by impregnating glass braid with varying thickness coatings (from 200 Å up to 1600 Å thick) of polyester resin, were tested with a DuPont Dynamic Mechanical Analyzer. The effects of the polyester resin thickness and silane treatments on the dynamic mechanical properties of the composites were evaluated. The results are supported by Fourier transform infrared spectroscopy of the composite materials. It is shown that both the concentration and the organo-functional group of the silane coupling agent influence the damping, storage, and loss moduli as well as the glass transition temperature (Tg) of the matrix resin in the closest vicinity to the glass/resin bondline. In the absence of a silane inner layer, a low Tg, 'soft' boundary layer exists due to inhibition of the polyester resin cure by the glass surface. It is noted that a reactive silane, such as γ-methacryloxypropyltrimethoxysilane, promotes the formation of a 'soft' or 'rigid' (high Tg) boundary layer, depending on the concentration of the silane in the treating solution. On the other hand, a non-reactive silane, such as methyltrimethoxysilane, produces a 'rigid' interphase in the entire range of concentrations of the silane solution. An attempt was made to correlate the dynamic mechanical properties of the boundary layer with the fiber/polymer interfacial shear strength. Upon pretreatment of glass fibers with silane coupling agents, the relative magnitude of the loss modulus, E", and the nature of the boundary layer (Tg) seem to be better indicators of efficient stress transfer from the polymer to the glass fiber in the composite system than tan δ. Efficient stress transfer is characterized by a low value of E" and 'soft' boundary layers. The results suggest that the mere presence of glass/polyester chemical bonding is insufficient to ensure effective stress transfer. A strong bond results from the synergistic effect of glass/silane/polymer chemical bonding and a 'soft' boundary layer.

Role of silanes in adhesion-Part I. Dynamic mechanical properties of silane coatings on glass fibers

The dynamic mechanical properties of glass fibers impregnated with y-methacryloxypropyltrimethoxy silane and methyltrimethoxy silane were studied as a function of the concentration of the silanes in the coating solution. An increase of the concentration of the silanes increases the molecular weight of the polymeric coatings, as well as the extent of their crosslinking, glass transition, modulus, and damping. The dynamic mechanical properties of y-methacryloxypropyltriethoxy silane show a correlation with the adsorption characteristics of the silane on an inorganic filler. It is demonstrated that dynamic mechanical measurements of the glass/silane composites, when combined with other instrumental approaches such as infrared spectroscopy and gel permeation chromatography, may provide valuable information on the composition, the structure, and the mechanical properties of silane coatings on a glass surface.