Addition Of Silane Research Articles

Spherically expanding flame in silane–hydrogen–nitrous oxide–argon mixtures

The effect of silane addition on the laminar flame speed (Su0) of flames propagating in hydrogen–nitrous oxide–argon mixtures has been investigated experimentally for the first time using the spherically expanding flame technique in a constant volume combustion chamber. Replacing hydrogen by silane and maintaining the equivalence ratio constant, much higher flame speeds, explosion peak pressures, and pressure rise coefficients were measured. A previously developed detailed reaction model has been updated based on ab initio thermodynamic properties calculations and collision limit violation analysis. The improved reaction model demonstrates encouraging performance in predicting the flame speed, with a mean absolute error below 11%. To explain the effect of silane addition on the flame dynamics, a number of parameters have been calculated including OH and H rate of production, heat release rate per reaction, and sensitivity coefficient on Su0. The dynamics of freely propagating flames in SiH4–H2–N2O–Ar mixtures is essentially controlled by reactions of the H–O–N chemical system: N2O+H=N2+OH, OH+H2=H2O+H, and N2O(+M)=N2+O(+M). Whereas silane addition does not influence much the rate of production of OH, it significantly modifies that of H with a number of pyrolytic chemical pathways of silicon hydrides, such as SiH+H2=SiH2+H and Si+H2=SiH+H, which act as sink of H atom as they proceed in the backward direction. The reactions forming SiO(s) and SiO2(s), such as SiO+OH=SiO2(s)+H and 2SiO=2SiO(s), are exothermic and significantly contribute to the temperature increase. The adiabatic, constant pressure flame temperature for mixture containing silane is significantly higher, up to several 100’s K. The increase of Su0 induced by silane addition seems to be mostly related to the large increase of the flame temperature which leads to higher energy release rate.

Effects of silane on reaction process and microstructure of metakaolin-based geopolymer composites

A series of metakaolin-based geopolymer (MG) organic-inorganic composites were prepared by incorporating with different contents of silane. The silane was used as coupling agent to recombine different components in geopolymer pastes. During the hydration process, the hydration heat evolution, structure and chemical compositions were obtained to characterize the reaction kinetics. The use of silane (APTES) retarded the geopolymer hydration significantly with the increase of silane content. Fourier transform infrared (FT-IR) spectroscopy and solid-state 29Si nuclear magnetic resonance (NMR) indicated that the tetrahedral structure ([SiO4]4- and [AlO4]4-) of aluminosilicate was decomposed and migrated and recombined to form a new tetrahedral network. SEM microscope images and EDS maps showed that the addition of silane enabled geopolymer to achieve a structural homogeneity, which resulted in the significant increase of the content of carbon and the formation of the chemical bonding reaction in organic-inorganic geopolymer composites.

Effect of Carbon Nanotube-Silane Addition on Mechanical Properties of Chloroprene Rubber-filled Carbon Black

Chloroprene-filled CNT rubber has been investigated for the electromagnetic shielding application. Nevertheless, there are continuous studies to overcome CNTs agglomeration, materials loss and air contamination issues generated during conventional melt compounding process. Thus, the current study proposes the usage of polar and low molecular weight ethanol solvent as dispersant for CNT fillers and silane-based Si-69 as coupling agent. Si-69 is a widely used fillers’ coupling agent because of its reliable performance in the industrial-scaled rubber compounding process. This study is to investigate the effect of carbon nanotube (CNT)-Silane addition as secondary fillers on tensile strength, elastic modulus and cure characteristics of hloroprene rubber (CR)-filled carbon black (CB) compound. The CR-filled CB was prepared by internal mixing, followed by roll-mill process in which CNT-Silane dispersion was added. For comparison, the samples of CR-filled CB without CNTs addition and with as-received CNTs addition were prepared and characterized. The CR composite added with CNT-Silane dispersion displayed tensile strength and elastic modulus (at 300% elongation) of 23 MPa and 18 MPa respectively, which are 4% higher than the CR composite added with as-received CNTs. The findings were supported by the FESEM micrograph of tensile fracture samples that showed the CNT-Silane addition produced better CNTs dispersion in the CR-filled CB compound. Furthermore, the usage of CNT-Silane improved the CR-filled CB compound processibility by reducing the minimum (ML) and maximum torque (MH) values from 0.34 and 1.11 N.m in as-received CNT samples to 0.32 and 1.04 N.m respectively in CNT-silane samples.

Imido silyl complexes of molybdenum: synthesis, structure, and unusual H2/silane exchange

Reaction of complex (ArN)Mo(H)(Cl)(PMe3)3 (1) with BPh3 and silane H3SiPh affords a new silyl complex (ArN)Mo(SiH2Ph)(Cl)(PMe3)2 (3) that catalyses facile H–H/Si–H exchange. EXSY experiments suggest that this exchange does not involve the classical pathways such as oxidative addition of hydrogen or silane to the complex or σ-bond metathesis. It is suggested that the exchange may occur in an FLP cage comprised by the complex and the silane.

Morphology, abrasion and corrosion resistance study of the plasma electrolytic oxidation films formed on pure titanium by adding silane in the electrolyte

Surface modification of pure Ti is performed with the addition of aminopropyl trimethoxy-silane (APS) in the anodic electrolyte to obtain plasma electrolytic oxidation (PEO) ceramic films at a median voltage of 200 V. The addition of silane in Na2SiO3 solution does not change the phase compositions of the PEO films while promoting the faster growth of both rutile and anatase, meanwhile smoother and thicker ceramic films with more regular pores on the outer layers are obtained as reflected by the X-ray diffraction spectra (XRD) and scanning electron microscopy (SEM) results, respectively. The wear resistance in dry friction condition of the PEO films with silane addition is improved as seen from their friction coefficient and abrasive track image; the increase in corrosion potential (Ecorr) and decrease in corrosion current density (Icorr) suggest the improvement of their resisting ability to corrosive media, attributing to the formation of compacter inner and outer layer films as supported by the electrochemical impedance spectroscopy. The results of attenuated total reflection-Fourier transform infrared spectra (ATR-FTIR) and X-ray photoelectron spectra (XPS) reveal that APS exists on the surfaces and among the defects of ceramic films by adsorption, self-condensation and/or chemical linkage (Ti–O–Si) as various states, therefore their existence and filling effects result in the improvement in their abrasive and corrosive resistances.

Development of pipe repairs using bonded metal plate – Part I: Shape factor, stiffness and surface treatment

This work aims to study the resistance of repairs with bonded plates in pipes with holes subjected to hydrostatic pressure. It is a promising alternative for application in low-risk repairs (up to 1 MPa). Due to the differences between the circumferential and transverse stresses in the pipes, the influence of the bonded plate area in the joint strength was evaluated, checking whether the shape factor occurs. The effect of plate thickness in the repair strength, besides the addition of silane on the plate surfaces, were also studied. Finally, considering a control plate based in the performed experiments, the surface treatment influence on the tubes was evaluated in the face of rupture pressure of the system. High hydrostatic resistance values were found, demonstrating the efficiency of the procedures used in the repair. The studies show little influence on the repair strength due to dimensions variation in different directions, and high influence on the surface treatment, stiffness and bonded area increase. The work aims to initiate the development of a new procedure for contingency repair with low risk.

Avaliação da resistência coesiva de reparos de resina composta utilizando silano como agente de união

Objetivo: Avaliar a resistência coesiva de reparos de resina composta utilizando silano como agente de união. Métodos: Foram confeccionados 48 blocos de resina compostas para dentina na cor A3,5 medindo 8 x 8 x 4 mm que em sequência foram divididos em 4 grupos segundo a técnica de reparo: somente adesivo convencional; ácido fosfórico 37%+adesivo convencional; ácido fosfórico 37%+silano+adesivo convencional; ácido fosfórico a 37% + adesivo universal. Após isso, os blocos foram restaurados com resina composta translúcida, sendo 24 imediatamente após a confecção do bloco e 24 após conservação em água destilada por 24 horas. Os espécimes foram submetidos a teste de microtração antes após termociclagem. Os materiais utilizados para realização do reparo foram analisados em um espectrometro Micro-Raman. Resultados: Os grupos contendo silano apresentaram melhores resultados ao teste de microtração quando comparados aos grupos sem adição de silano (P < 0,05). No espectrofotômetro Micro-Raman o silano e o adesivo universal apresentaram picos aumentados de Si-O-Si quando comparados ao adesivo convencional. Conclusão: Pode-se concluir que a presença do silano interfere positivamente nos reparos de resinas compostas.

Synthesis of Stereodefined Trisubstituted Alkenyl Silanes Enabled by Borane Catalysis and Nickel Catalysis.

Regioselective and stereoselective synthesis of trisubstituted alkenyl silanes via hydrosilylation is challenging. Herein, we report the first β-anti-selective addition of silanes to thioalkynes with B(C6F5)3 as the catalyst. The reaction shows broad substrate scope. The products were proven to be useful intermediates to other trisubstituted alkenyl silanes by Ni-catalyzed stereoretentive cross-coupling reactions of the C-S bond. A mechanism study suggests that nucleophilic attack of thioalkyne to an activated silylium intermediate might be the rate-determining step.

Enhanced electrolyte performance by adopting Zwitterionic lithium-silica sulfobetaine silane as electrolyte additive for lithium-ion batteries

Zwitterionic lithium-silica sulfobetaine silane is fabricated by first synthesizing zwitterion sulfobetaine silane, grafting it onto hydrophilic silica to form silica sulfobetaine silane, and then lithiating the silica sulfobetaine silane. The resultant lithium-silica sulfobetaine silane additive is used as a liquid electrolyte additive in lithium-ion batteries with varying weight percentages in 1 M LiPF6 (ethylene carbonate/dimethyl carbonate = 1:1). The electrolytes with the lithium-silica sulfobetaine silane shows higher ionic conductivities (1.92 × 10−2 S cm−1 at RT and 1.62 × 10−3 S cm−1 at −20 °C) and greater electrochemical stability (anodic limit at ~5.5 V vs. Li/Li+) than the pure electrolyte (anodic limit at ~4.6 V vs. Li/Li+). The discharge capacity of the lithium nickel cobalt manganese oxide/graphite cell is improved at higher C-rates with the addition of lithium-silica sulfobetaine silane due to increased ionic conductivity. The lithium nickel cobalt manganese oxide/graphite cells with the lithium-silica sulfobetaine silane additive also show stable cycling performance. These findings warrant the use of lithium-silica sulfobetaine silane as an electrolyte additive in lithium-ion batteries.

Remarkable improvement of organic-to-inorganic conversion of silicone rubber at elevated temperature through platinum-nitrogen catalytic system

Organosilicon materials with high capacity of organic-to-inorganic conversion at elevated temperature are always favorable in the field of high-temperature-resistant materials, flame retardant materials, chemical engineering and functional materials in electrical engineering. In this work, it was found out that the platinum-nitrogen catalytic system could obviously enhance the organic-to-inorganic conversion efficiency of silicone rubber (SiR) at elevated temperature. The residual rate of Pt/N/SiR (SiR containing 0.33 phr Karstedt's catalyst (Pt) and 2 phr nitrogenous silane (N)) at 1000 °C was significantly improved from 3.0% to 44.8% in comparison with SiR and its thermal stability was also enhanced. DLS, TEM and UV–vis absorption spectrometry revealed that the platinum in Karstedt's catalyst would aggregate at elevated temperature and deteriorate its catalytic activity for organic-to-inorganic conversion of SiR. And the addition of nitrogenous silane can efficiently inhibit the aggregation and retain the high catalytic efficiency of platinum. A thorough TG-FTIR study, together with SEM/EDX and XPS analyses suggested that the platinum-nitrogen system might suppress the intramolecular cyclic transition and enhance the radical coupling between polymer chains of SiR during thermal degradation, which resulted in the high capacity of organic-to-inorganic conversion of Pt/N/SiR at elevated temperature.

Impacts of recycled crumb rubber powder and natural rubber latex on the modified asphalt rheological behaviour, bonding, and resistance to shear

The objective of this study is to investigate the rheological properties, bonding and resistancetoshear of the rubberized modified binders under different conditions. A base asphalt binder with penetration grade 60/70 was utilised in this study. The crumb rubber and natural rubber latex were added at different percentages for the modified bitumen production, and computed based on the mass of bitumen. Silane additives at the rate of 0.1% by mass of asphalt binder were used as a surfactant. A series of rheological properties and recovery test were conducted on all binders. While bond test and Layer-Parallel Direct Shear (LPDS) test were carried out in order to simulate the crack movement of pavement. The results show that the addition of crumb rubber and latex positively impacts the performance of the asphalt binder. The crumb rubber and natural rubber latex modified asphalt binder has comparatively identical elastic recovery outcomes, while it also helps in enhancing the stiffness in terms of softening and penetration value. However, natural rubber latex modified asphalt binder performed much better than crumb rubber modified asphalt binder in terms of torsional recovery. Whereas, rotational viscosity test has been useful in adopting the suitable temperature which is 160 °C in order to satisfy the needs of better workability and to ensure it is pumpable. Storage stability test proved that the modified asphalt binders are homogenous since the temperature differences are less than 5 °C. The dynamic shear rheometer (DSR) test proved that the modified asphalt binder has better resistance to rutting. Through DSR findings and activation energy, the modified asphalt binder were catogorize as less susceptible to temperature changes. Finally, the crumb rubber modified asphalt binder did well in terms of bonding strength, while the natural rubber latex modified asphalt binder performed well in terms of resistance to shear. Overall, both rubberized modified binders performed better than the control sample.

Copper-Catalyzed Asymmetric Formal Hydroaminomethylation of Alkenes with N,O-Acetals to Access Chiral β-Stereogenic Amines: Dual Functions of the Copper Catalyst

Chiral amines are synthetically versatile intermediates used for the preparation of a wide range of biologically active compounds and drugs. Compared with the well-developed synthesis of α-stereoge...

Effect of surface treatments and filler loading on the properties of hemp fiber/natural rubber composites

The aim of this present work was to study the effect of surface treatment methods, i.e., silane and permanganate on curing characteristics, dynamic mechanical, mechanical morphological and thermal properties of hemp fiber filled natural rubber composites. Hemp fiber surfaces were pretreated with an alkali solution and followed by a KMnO4 solution or (3-triethoxysilylpropyl) tetrasulfide (Si69). After that, the chemical, physical and morphological properties of untreated and treated hemp fiber samples were investigated by attenuated total reflectance-Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy. It was found that the KMnO4 and silane (Si69) treatments affected the surface characteristics of hemp fibers. The curing characteristics of the rubber composites, i.e., scorch and curing times increased with increased fiber loading, except for 15 parts per hundred of rubber (phr) fiber level. The curing characteristics improved with the addition of KMnO4 or silane treated hemp fiber compared to unfilled natural rubber composites. At 5 phr fiber loading, it was found that silane treated hemp fiber filled natural rubber composite showed greater tensile strength and crosslink density in comparison with KMnO4 treated and untreated hemp fiber filled rubber composites. Good interface interaction between the silane treated hemp fiber and rubber matrix was observed in SEM images. Additionally, the thermal stability of rubber composites was unaltered with the incorporation of KMnO4 or silane treated hemp fibers.

SILICA-REINFORCED NATURAL RUBBER TIRE TREAD COMPOUNDS CONTAINING BIO-BASED PROCESS OILS. I: ASPECTS OF MIXING SEQUENCE AND EPOXIDE CONTENT

ABSTRACT A bio-based process oil for rubber compounds is one of the compounding ingredients to be used toward an eco-friendly and more sustainable rubber technology. This work investigates epoxidized palm oil (EPO) as an alternative for petroleum-based process oil in silica-reinforced natural rubber (NR) tire tread compounds. The effect of different incorporating steps of EPO on the properties of the rubber compounds is first studied, taking into account that the polar functional groups in the oil molecules may interact with the silanol groups on the silica surface. The properties of silica-reinforced NR compounds with EPO oil are compared with that of reference mixes with treated distillate aromatic extract (TDAE) and without oil. The compounds with EPO show a lower viscosity, filler–filler interaction, and flocculation rate constant but higher cure reaction rate constants compared with the compound with TDAE. The results indicate that the epoxide groups in EPO interact with the silanol groups on the silica surface, promoting a greater shielding effect on the polar surface and thus better silica dispersion and less interference with the vulcanization reaction. The different incorporating steps of EPO show no significant effect on the viscosity, filler–filler interaction, or flocculation rate constant but clearly affect the extent of crosslinking, as indicated by the cure torque difference. The presence of EPO in an early stage of the mixing together with the first half addition of silica and silane results in the lowest cure torque difference, modulus, and tensile strength (i.e., the highest tan δ at 60 °C), which indicates a possible obstruction for the interaction between the silanol groups and silane coupling agent by the EPO molecules. Comparing EPO with different epoxide contents in the range of 1–3 mol%, the increase in epoxide content gives similar Payne effects but enhances the cure reaction, resulting in improved tensile properties and tan δ at 60 °C. The results clearly prove that EPO can be used as a TDAE alternative.

CO Displacement in an Oxidative Addition of Primary Silanes to Rhodium(I).

The rhodium dicarbonyl {PhB(OxMe2)2ImMes}Rh(CO)2 (1) and primary silanes react by oxidative addition of a nonpolar Si-H bond and, uniquely, a thermal dissociation of CO. These reactions are reversible, and kinetic measurements model the approach to equilibrium. Thus, 1 and RSiH3 react by oxidative addition at room temperature in the dark, even in CO-saturated solutions. The oxidative addition reaction is first-order in both 1 and RSiH3, with rate constants for oxidative addition of PhSiH3 and PhSiD3 revealing kH/ kD ∼ 1. The reverse reaction, reductive elimination of Si-H from {PhB(OxMe2)2ImMes}RhH(SiH2R)CO (2), is also first-order in [2] and depends on [CO]. The equilibrium concentrations, determined over a 30 °C temperature range, provide Δ H ° = -5.5 ± 0.2 kcal/mol and Δ S ° = -16 ± 1 cal·mol-1K-1 (for 1 ⇄ 2). The rate laws and activation parameters for oxidative addition (Δ H⧧ = 11 ± 1 kcal·mol-1 and Δ S⧧ = -26 ± 3 cal·mol-1·K-1) and reductive elimination (Δ H⧧ = 17 ± 1 kcal·mol-1 and Δ S⧧ = -10 ± 3 cal·mol-1K-1), particularly the negative activation entropy for both forward and reverse reactions, suggest the transition state of the rate-determining step contains {PhB(OxMe2)2ImMes}Rh(CO)2 and RSiH3. Comparison of a series of primary silanes reveals that oxidative addition of arylsilanes is ca. 5× faster than alkylsilanes, whereas reductive elimination of Rh-Si/Rh-H from alkylsilyl and arylsilyl rhodium(III) occurs with similar rate constants. Thus, the equilibrium constant Ke for oxidative addition of arylsilanes is >1, whereas reductive elimination is favored for alkylsilanes.

Effect of hierarchical ZSM-5 zeolite support on direct transformation from syngas to aromatics over the iron-based catalyst

In this work, hierarchical ZSM-5 zeolites featured by different Si/Al ratio and mesoporosity were prepared via soft template. The hierarchical zeolites supported iron catalysts were prepared by incipient impregnation and their properties were studied by XRD, XRF, BET, SEM, TEM and NH3-TPD. The resultant catalysts were used to convert syngas into aromatics. The results indicated that zeolite with high acidity could increase the selectivity to aromatics in the oil product. By using low Si/Al ratio catalyst Fe-Z-50-5, 70.7% of selectivity to aromatics can be obtained in oil product. With the increase of mesoporosity, selectivity of C5+ oil product also increased. By adjusting silane addition, 23.2% selectivity of aromatics was obtained in hydrocarbon over Fe-Z-80-15 catalyst, which is the highest among all the same catalyst system under low H2/CO syngas (H2/CO = 1). However, hierarchical zeolite support with different Si/Al ratio and mesoporosity have little effect on the distribution of aromatic product.

Study in the Durability of Silane-Based Mortar

Abstract This article investigates the durability properties of mortar containing three types of silanes as integral additives. Compared with the plain mortar, mortar samples with silanes exhibited better performance when subjected to freezing-thawing cycles and chemical and carbonation corrosion. The addition of silanes also results in the formation of chemical bonding across the interface, which is helpful for improving crack resistance. Additionally, mortar samples with γ-Glycidoxypropyl methyldimethoxysilane (GDMMS) show better freezing-thawing resistance and chemical corrosion resistance than do mortar samples with γ-aminopropytriethoxysilane and 3-(Trimethoxysilyl)propyl methacrylate, because of the more effective interface between the GDMMS and mortar. For mortar samples with silanes, the effect of the types and quantity of silanes on the crack resistance of mortar and carbonation corrosion is not obvious. Scanning electron microscopy images show that silanes perform the networking and “coupling” effect to hold mortar particles, resulting in the improvement of mortar durability.

Effect of vinyltrimethoxy silane as a coupling agent on the mechanical and electrical properties of acrylic rubber

When there is a need for enhancing the adhesion between a polymeric material and the filler, silane coupling agents are the best choice. In order to enhance the adhesion between acrylic rubber (ACM) and silica, vinyl trimethoxy silane (VTMS) can be used for this purpose. Acrylic rubber was prepared by emulsion polymerization. VTMS was added during the polymerization process to copolymerize with ACM. VTMS was added in different per cent; 0, 0.25, 0.5, 1.0 and 2.0 %. The effect of adding different percentages of VTMS on the mechanical, thermal and mechanical properties was monitored. Mechanical properties were significantly improved due to silane incorporation to the acrylic rubber matrix. The thermal stability of acrylic rubber increased due silane addition. Electrical measurements revealed that the volume resistivity, dielectric strength and breakdown voltage were also increased.

The effect of nanoperlite and its silane treatment on thermal properties and degradation of polypropylene/nanoperlite nanocomposite films

The main goal of this study is to observe the exact effect of nanoperlite and its silane treatment on thermal behavior and degradation mechanism as well as thermomechanical properties of nanocomposites. In this regard, polypropylene (PP) with various contents of untreated nanoperlite and silane treated nanoperlite were prepared using a twin-screw extruder and an extrusion film blew machine. Regardless of the type, the Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) tests show no chemical reaction between PP and nanoperlite and relatively good dispersion of nanoparticles was obtained in the system. The results of thermal studies represent a reduction in all the properties of nanoperlite/PP nanocomposites including thermal stability, while, the addition of silane treated nanoperlite shows less reduction and better thermal stability. Based on Flynn-Wall-Ozawa method, thermal degradation kinetics and mean activation energies of the untreated nanoperlite filled nanocomposites show higher values. Finally based on thermomechanical studies, treated nanoperlite-filled nanocomposites show lower values for tan D comparing to untreated nanoperlite-filled nanocomposites, as the storage modulus is reinforced and the loss modulus decreased. Overall, nanocomposites with 2–4% of treated nanoperlite showed nearly the same behavior of 4–6% of untreated nanoperlite filled nanocomposites and due to better dispersion, thermal and morphological properties, these films can be proper alternatives for packaging industries.

Fiber Surface Modification; Characterization of Rattan Fiber Reinforced Composite

Increasing the awareness of global warming and the depletion of petroleum resources had made many researchers focuses on using natural materials such as rattan. Its an edible fibers are prepared to reinforce matrix yielding composite products within the aid of epoxy based resin and hardener which also perform as catalyst. The fibres are previously conducted an alkali treatment, this was considered to enhance the cohessiveness of fibers to matrix. Silane and dimethylethanolamine (DMEA) as an adhesives booster is respectively added to the composite formula. The specific purpose of this research is to know the influence of addition of Silane and DMEA to the final properties of composite; flexural, tensile strength, elongation at break, hardness, and thermal. From the test results it is found that Silane keeps the matrix amorphous, while the addition of DMEA formed crystalline polymer. The ultimate property of the composites are found also depends on fiber woven pattern.