Kinds Of Silane Coupling Agents Research Articles

Synergistic flame‐retardant effects between silane coupling agents modified expanded graphite and Pt catalyst in silicone rubber composites

AbstractIn this work, different kinds of silane coupling agents modified expanded graphite (MEG) fillers were successfully prepared and then incorporated into silicon rubber matrix to fabricate flame‐retardant composite materials (SR/MEG). The inserted MEG fillers with siloxane chains exhibited good compatibility with the silicon rubber matrix, which cannot only reduce the negative impact of adding fillers on mechanical properties but also endow the silicon rubber composites with ideal flame retardancy. Subsequently, platinum (Pt) catalyst was incorporated into the SR/MEG composites to prepare SR/MEG/Pt composites, and the synergistic effects of MEG and Pt catalyst on the thermal stability, flame retardancy, and combustion behavior of silicon rubber composites were systematically investigated. The target SR/MEG/Pt composite with appropriate addition of MEG and Pt catalyst can obtain relatively high char residue of 41.9% and limiting oxygen index value of 29.6%, as well as achieve V‐0 rating in the vertical combustion test, owing to the formation of expanded and dense silicon–carbon protective layer under the catalysis of Pt catalyst. Moreover, the cone calorimeter test results showed that the peak of heat release rate and total heat release of SR/MEG composites were further reduced after the addition of an appropriate amount of Pt catalyst, manifesting the good synergistic effect of MEG and Pt catalyst on the flame retardancy performance of silicon rubber. The method proposed herein may provide a promising way for fabricating high‐performance flame‐retardant silicone rubber materials.

Modified SiO2 microspheres/polyacrylate resin composites for the enhancement of oil-absorbing performance

Inserting inorganic materials into the skeleton of oil-absorbing resin (OAR) would weaken the interchain winding of polymer, regulate the pore channel structure, and thus enhance the oil-absorbing performance. However, the effects of surface modifiers on the oil-absorbing ability have been rarely explored. Herein, SiO2 microspheres coated with three kinds of silane coupling agents (3-aminopropyltriethoxysilane (APTES), γ-(methacryloxypropyl) trimethoxy silane (MEMO) and chlorotrimethylsilane (TMCS)) were composited with P(SMA-co-BA-co-ST) (octadecyl methacrylate (SMA), butyl acrylate (BA) and styrene (ST)). The as-prepared composite resin microspheres (OAR-APTES-SiO2, OAR-MEMO-SiO2 and OAR-TMCS-SiO2) were fully characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), optical microscopy (OM) and thermal gravimetric analysis (TGA). The results showed that the average particle sizes of the as-prepared SiO2 microspheres were nearly 300 nm and the silane coupling agent of APTES exhibited the best surface modification for SiO2 microspheres (grafting rate reached 16.78%). While, the average particle sizes of composite resins (OAR-APTES-SiO2, OAR-MEMO-SiO2 and OAR-TMCS-SiO2) were nearly 1.5 mm, 2 mm and 2.5 mm, respectively. Meanwhile, composite resin OAR-APTES-SiO2 showed the highest saturated oil-absorbing capacities, which were calculated to be 44.97, 38.12, 27.29 and 22.86 g/g for CCl4, CHCl3, CH2Cl2 and gasoline, respectively, under the optimal adding amount of SiO2 (ω(SiO2) = 0.8%), reaching more than 90% of the saturated oil-absorbing capacity in 30 min. Meanwhile, the oil-absorbing capacity of composite resin is 1.34 times higher than that of bare acrylic resin. It can be recycled 7 times without the obvious decrease in oil absorption ability. This study provides a novel method for the preparation of composite materials with high stability, high oil-absorbing capacity and low-saturation oil-absorbing time by regulating the resin pore structure.

Regulating and Controlling the Microstructure of Nanocellulose Aerogels by Varying the Intensity of Hydrogen Bonds

Because of the fascinating properties and tremendous application potential of nanocellulose aerogels (CAs), research into them has exploded. However, regulating and controlling their microstructure remain challenging. Herein, the strategy of regulating the strength of hydrogen bonding was used to investigate the cause of cellulose nanofiber (CNF) aggregation. Three kinds of silane coupling agents with different tail functional groups were employed to modify CNFs. The hydrogen bond fraction of CAs decreased from 0.41 to 0.33, indicating a decrease in the intensity of hydrogen bonding. Also, the CA with a 3D-web-like structure was obtained. The specific surface area of the aerogels increased from 44.36 to 99.37 m2/g, showing that the aggregation was limited. In parallel, superior mechanical properties and thermal insulation were obtained. These results showed that varying the intensity of the hydrogen bond could inhibit the aggregation of the CA skeleton structure. The improvement of the specific surface area will expand its application in catalyst support, environmental remediation, heat insulation, and other fields. This method paved the way for future studies on the control of the micro-structure of CAs.

Reactivities of silane coupling agents in the silica/rubber composites: Theoretical insights into the relationships between energy barriers and electronic characteristics.

Si69 and Si75, typical commodities of silane coupling agents, are often employed in tire recipes to work as the bridges connecting silica and polymers, with which rolling resistance and wet traction are enhanced without loss in abrasion resistance. In this article, the reactivities of Si69 and Si75 with silica and various rubbers were theoretically investigated by using density functional theory (DFT). When the agents were coupled with silica, not only the acid+water condition but also the pure acid condition was confirmed to readily trigger the condensation reactions. The corresponding Gibbs free energy barriers were related to the charge distributions of reaction regions. As the agents suffered from the homolysis of central SS bonds, the generated single-S-tailer radicals (RS·) showed significantly higher reactivities of both the radical addition and the α-H transfer reactions with rubbers, due to the stronger radical philicities of the terminal sulfur radicals with larger condensed local softnesses [s0 (S)]. When the agents underwent the heterolysis of central SS bonds, the terminal sulfur anions with smaller s- (S) indices, however, facilitated the nucleophilic addition reactions with rubbers. Several derivative indices based on the condensed local softnesses were also proposed here to shed light on the reactivities from the viewpoint of the relationship between energy barriers and electronic characteristics. The above findings pave the way for the design of new kinds of silane coupling agents using computer-aided techniques, and meanwhile, provide references for the practical application of Si69 and Si75 to the silica/rubbers systems.

Cellulose Nanofiber-Assisted Dispersion of Halloysite Nanotubes via Silane Coupling Agent-Reinforced Starch-PVA Biodegradable Composite Membrane.

HNTs (halloysite nanotubes) are widely used in reinforcing material, often used in material reinforcement and particle loading. However, their easy agglomeration causes them to have great limitations in application. In this work, two kinds of silane coupling agents (KH560 and KH570) were introduced to graft the CNF/HNT (cellulose nanofiber) nanoparticles used to reinforce the starch-polyvinyl alcohol (PVA) composite membranes. The mechanical properties, water resistance properties and thermal performance of the composite membrane were tested. The results showed that the CNF/HNTs nanoparticle system modified by two silane coupling agents enhanced the tensile strength (TS) of the starch–PVA composite membranes by increments of 60.11% and 68.35%, and, in addition, the water resistance of starch–PVA composite membrane improved. The introduction of chemical bonds formed associations and a compact network structure, which increased the thermal stability and the crystallinity of the starch–PVA composite membrane. In the study, we creatively used CNF to disperse HNTs. CNF and HNTs were combined under the action of the silane coupling agent, and then mixed into the starch–PVA membranes matrix to prepare high-performance degradable biological composite membranes.

Preparation and characteristics of sepiolite-waterborne polyurethane composites

Abstract A kind of organic/inorganic composite material composed of waterborne polyurethane and sepiolite was prepared in this work. Sepiolite was organically modified by three kinds of silane coupling agents, and then compounded with waterborne polyurethane through layer-by-layer method in order to prepare composite materials. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) show the crystal and chemistry structure of sepiolite samples, and confirmed the preparation of organic sepiolite. Scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS) showed the surface microstructure and elemental content of sepiolite and organic sepiolite, and was consistent with the XRD results. Transmission electron microscope (TEM) examination of waterborne polyurethane composites surfaces showed that sepiolite particles were regularly dispersed in the waterborne polyurethane matrix. Thermal resistance of waterborne polyurethane composites was determined by thermogravimetry analyzer (TG) and derivative thermogravimetry analyzer (DTG), differential scanning calorimetry (DSC), gas chromatography (GC), and mass chromatography (MS). Mechanical behavior was examined by tensile strength tester, showed higher break strength than that of the control waterborne polyurethane. Therefore, organically modified sepiolite was considered to be a kind of wonderful inorganic material that could be used to improve the thermal stability and mechanical property of polymer.

Preparation and Characterization of TiO₂ Nanowires Modified Organically with Coupling Agents.

Anatase-type one-dimensional TiO₂ nanowire was prepared by hydrothermal method. The nanowires were modified by three kinds of silane coupling agents, such as KH550, KH560 and KH570. Flocculation was caused when the amount of modifier reached a certain level. When KH570 was used at 3.0 percent, at 80 °C, 4 h, and pH value between 9 and 10, modified nanowires had the highest 56.5 percent lipophilization degree, the lowest 0.562 per/nm² surface hydroxyl number, and the maximal 121.2° static contact angle.

Reusable 3D silver superposed silica SERS substrate based on the Griess reaction for the ratiometric detection of nitrite.

When nitrite is ingested and absorbed by the body, it can be converted into highly toxic nitrosamines (carcinogens, teratogens, and mutagens), posing health risks to the general population. Therefore, it calls for establishing a method for determination of nitrite. In this paper, the glass-SiO2-Ag surface-enhanced Raman scattering (SERS) substrate with a large number of "hot spots" were prepared by two kinds of silane coupling agents. The SERS substrate had high sensitivity and repeatability. Silicon dioxide supported the silver nanoparticles (Ag NPs), which increased surface roughness of the substrate, generated a great quantity of hot spots and enhanced the SERS signal. In the SERS spectrum, the intensity ratio of the two characteristic peaks (1287cm-1 and 1076cm-1) had a good linear correlation with the logarithm of the concentration of nitrite, R2 = 0.9652. The recoveries of 50μM and 100μM nitrite in three kinds of foods, three kinds of cosmetics and tap water were 90.9-105.3%.

Enhancing TFC membrane permeability by incorporating single-layer MSN into polyamide rejection layer

A new kind of thin film composite membrane (TFC) was prepared through a simple layer-by-layer assembly method. Vinyltrimethoxysilane (VTMS), a kind of silane coupling agent, was grafted on PVDF membrane surface through free radical polymerization method firstly. Then, mesoporous silica nanoparticles (MSN) were uniformly grafted on surface of VTMS/PVDF membrane through reacting with the methoxide group (Si-OCH3) of VTMS. Under the optimized grafting conditions, the MSN grafted density can reach up to 8.73 mg/dm2. Eventually, the MSN were embedded into polyamide rejection layer through an interfacial polymerization process. The prepared MSN-TFC membrane has excellent permeability and desalination properties. Furthermore, this research provides a new pathway to incorporate MSN into polyamide rejection layer.

Effect of silane treatment on mechanical properties and thermal behavior of bamboo fibers reinforced polypropylene composites

In this work, the surface of the bamboo fibers (BF) was treated with three kinds of silane coupling agents terminated with amino functional groups (KH550), epoxy functional groups (KH560), and methyl functional groups (KH570) to improve fiber–matrix adhesion. The effects of silane treatment on the mechanical properties and thermal behavior of BF/polypropylene (PP) composites were investigated. Mechanical test results showed that the order of modification effectiveness was KH570 > KH550 > KH560. KH570 treated fiber composite exhibited the best mechanical properties. The tensile strength and flexural strength of 5 wt% KH570 treatment reached to 36.1 and 54.7 MPa, which were 15.4% and 23.6% higher than those of UBF/PP composites. Simultaneously, the thermal stability increased from 467.0°C (UBF) to 470.6°C (KH-570 treated BF). An increase in crystallization temperature (1.7°C) and a decrease in crystallinity (5.8%) occurred upon the addition of 5% KH570 silanes treated bamboo fibers.

Scalable in situ condensation fabrication of amorphous SiOX@C microbeads derived from organic silane coupling agents for lithium-ion storage

In the past few years, silane coupling agents are often used to modify the surface of silicon materials; however, researches in preparation of SiOX-based materials pyrolyzed from silane coupling agents are seldom reported. Hence, in order to prepare amorphous SiOX@C anodes for Li-ion storage, we adopted three kinds of silane coupling agents as organic silicon sources. The results show that silane coupling agents with vinyl group is the optimum organic silicon source. Owing to the strong chemical bonds of Si–O–C, amorphous SiOX particles are uniformly embedded in carbon matrix, forming monodisperse microbeads architecture with good buffer abilities. Therefore, the V-SiOX@C anodes derived from silane coupling agents with vinyl groups show good electrochemical performance, retaining a reversible discharge capacity of 940 mAh g−1 at a current density of 100 mA g−1 after 200 cycles, and it still depicts a good long-term cycling durability, maintaining 739 mAh g−1 at a current density of 400 mA g−1 after 400 cycles.

Modifying wood veneer with silane coupling agent for decorating wood fiber/high-density polyethylene composite

Because of the smooth, dense, and nonpolar surface of wood-plastic composites (WPCs), it is challenging to form an efficient bonding interface between the WPC and the material of the wood veneer by using traditional adhesives. In this study, two kinds of silane coupling agents (r-aminopropyl triethoxy silane, production number KH550; and trimethoxy vinyl silane, production number A171) and dicumyl peroxide were used to improve the bond between the wood fiber/high-density polyethylene (WF/HDPE) composite and the wood veneer. The attenuated total reflection-Fourier transform infrared spectroscopy curve shows that the two kinds of silane coupling agents were grafted to the surface of the wood veneer, and the contact angle between distilled water and the veneer surface increased from 46° to greater than 120° after treatment. The bonding strength between the treated veneer and the WF/HDPE composite was significantly enhanced, and samples treated with A171 had higher bonding strength than those treated with KH550. The greater the volume of wood fiber in the WF/HDPE, the poorer the bonding strength of the veneer and the lower its water resistance. Images from a scanning electron microscope show that the silane coupling agent A171 can induce a denser interface between the wood veneer and the WF/HDPE composite.

Hydrolysis kinetics of silane coupling agents studied by near-infrared spectroscopy plus partial least squares model

A method of Fourier transform near-infrared (FT-NIR) spectroscopy combined with partial least squares (PLS) model was successfully applied to investigate the hydrolysis kinetics of four kinds of silane coupling agents (phenyltriethoxysilane, vinyltriethoxysilane, 3-mercaptopropyltriethoxysilane, 3-chloropropyltriethoxysilane) in an acid-catalyzed EtOH system. The fast scanning speed and high sensitivity of the FT-NIR spectroscopy, and the powerful data processing ability of the PLS, enabled the method to quantitatively and accurately catch the fast changing H2O concentration during the hydrolysis processes without delay, realizing the study of the fast-paced hydrolysis reactions of the silane coupling agents. The results showed that electrophilic substitution occurred in the hydrolysis reactions, which followed second-order reactions and greatly depend on the catalyst concentration and reaction temperature. The hydrolysis rate constants, activation energy, and Arrhenius Frequency factors were gained. In conclusion, the FT-NIR PLS model is a powerful tool for hydrolysis kinetics researching of the silane coupling agents.

Silane Coupling Agents Modified Silica and Graphene Oxide Materials for Determination of Sulfamerazine and Sulfameter in Milk by HPLC

Silica and graphene oxide were separately modified by using three different kinds of silane coupling agents, including (3-chloropropyl)-trimethoxysilane (NQ54), 3-methacryloxypropyltrimethoxysilane (KH570), and (3-aminopropyl) triethoxysilane (KH550). The characterization of obtained materials was tested by Fourier transform infrared spectroscopy and scanning electron microscopy, and the electronegativity was determined by Zetasizer Nano ZSP. The obtained materials were used to determine the sulfamerazine and sulfameter by ultrasonic-assisted dispersive solid-phase extraction. The static sorption experiment showed that the graphene oxide modified by NQ54 had a good sorption ability for two targets. Under the optimal condition, a reliable analytical method was developed for high recognition towards two targets in milk by NQ54-modified graphene oxide with satisfactory extraction recoveries (sulfamerazine 96.75% and sulfameter 94.08%, respectively). The recoveries of proposed method at three spiked levels were 92.16–101.71% and 92.95–103.81%, respectively, with the relative standard deviation less than 3.20%. It was indicated that graphene oxide modified by NQ-54 showed better performance for two targets, and the proposed method had been successfully applied for the determination of sulfonamides sample in milk.

Durable superhydrophobic and underwater superoleophobic cotton fabrics growing zinc oxide nanoarrays for application in separation of heavy/light oil and water mixtures as need

Based on controlling ZnO nanoarrays morphology and employing fluorine-free modification agent, superhydrophobicity in air and superoleophobicity under water were successfully achieved on the prepared cotton fabric surfaces via a two-step hydrothermal reaction. To increase adhesion between ZnO crystal layer and substrate surface, two kinds of silane coupling agents (hydrophobic TTOP-12 and hydrophilic KH550) were added selectively in the pretreatment process. The as-prepared fabric exhibited great tolerance and durableness towards external harsh environments, such as mechanical abrasion, UV radiation, immersion of acid or alkali, and high temperature. In comparison, superhydrophobic fabrics showed superior separation effect for heavy oil and water mixture, while underwater superoleophobic fabric can also show efficient separation of water and light oil with high separation efficiency and flux. In a word, heavy/light oil and water mixtures can be separated efficiently as need by choosing cotton fabrics with various wettabilities.

Preparation and characterization of modified SiO2 nanospheres with dichlorodimethylsilane and phenyltrimethoxysilane

In this study we synthesized spherical nanosilica by the Sol-Gel method using tetraethyl orthosilicate (TEOS), and the average particle diameter was measured by scanning electron microscopy (SEM). The surface of silica nanoparticles was modified with two kinds of silane coupling agents: dichlorodimethylsilane (DCDMS) and phenyltrimethoxysilane (PhTMS). We investigated the effect of the type of silane coupling agent with different functional groups (alkoxy or chloro) on the surface properties of modified silica by various analytical methods, i.e., FT-IR spectroscopy, CHN analysis, UV-visible spectra and thermogravimetric analysis (TGA) measurements. The particles modified with DCDMS showed larger grafting density from CHN analysis and higher weight loss from TGA measurement indicating the higher content of silane grafted on the surface of SiO2 nanoparticles. We suggest that the variations in grafting were dependent on the silane condensation which indicating the greater ability of condensation reaction of DCDMS with OH groups of silica rather than PhTMS.

Manufacturing a high performance film of CaO-B2O3-SiO2 glass-ceramic powder with surface modification for LTCC application

The present work was oriented to develop a high-performance film for LTCC application through using a kind of silane coupling agent (SCA) to modify the CBS (CaO-B2O3-SiO2) glass-ceramic powders in tape casting process. The coupling mechanism of the silane coupling agent interacting with the powders was illustrated in detail, and the optimum amount of additions was determined by the infrared transmittance and contact angle experiment. The rheological properties of suspensions, the compactness and tensile breaking strength of the green tape were texted by using a number of quantitative and qualitative instruments. Furthermore, when the green tapes sintered at 820°C, the sintering characteristics and microwave properties of sintered body with different SCA additions was also analyzed. Based on the experimental results, it revealed that the powders modified by SCA with 1.5wt% additions could induce the most excellent performance of film, with the density at 1.57g/cm3 and the tensile strength at 2.57MPa, possessing the highest density and best microwave properties of sintered body: the density of sintered body was 2.48g/cm3, the dielectric constant and dielectric loss was εr=5.93, tanδ=8×10−4 at 12Hz.

Green fabrication of ultraviolet curable epoxy acrylate-silica hybrid coatings

Abstract Ultraviolet (UV) curable organic-inorganic hybrid materials have attracted increasing researchers' attention due to the environmental advantages and extensive application potential. In this work, a novel green fabrication of UV curable epoxy acrylate (EA)-silica hybrid coating via a sol-gel process induced by photochemical reaction was presented. The inorganic phase, silica was formed at present of an iodonium salt and tetraethyl orthosilicate, avoiding the application of acid or base in traditional synthesis method. The hybrid coatings were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and thermogravimetric analysis(TGA). Three kinds of silane coupling agents including KH-550, KH-560 and KH-570 were investigated to modify the silica sol. The distribution of SiO 2 in the hybrid coating with KH-570 modification is most homogeneous. TGA results indicate that the hybrid coating with 10% of silica exhibits the most excellent thermal stability. The effects of adding content of silica on the hybrid film's tack free time and hardness were also investigated for the preliminary study.

Surface modification of silicon carbide with silane coupling agent and hexadecyl iodiele

In this paper, two kinds of silane coupling agents, namely 3-aminopropyl triethoxysilane (KH550) and 3-mercaptopropyl trimethoxysilane (KH590), were adopted as preliminary modifiers to improve the hydrophobic surface properties of silicon carbide (SiC) powder for the first step. The factors that influence the modification effects were investigated by measuring the contact angle. The results showed that KH590 has a better effect than KH550 for the hydrophobic modification of SiC, and the contact angle improved most after SiC powder was reacted with 0.3g KH590 at 75°C in aqueous/alcohol solution for 4h. On account of further enhancement of hydrophobicity, the study was focused on utilizing nucleophilic substitution between KH590 and hexadecyl iodiele to extend the length of alkyl chain. Compared with using KH590 alone, SiC powder modified by KH590 and hexadecyl iodiele showed better water resistance with an increase of contact angle from 106.8° to 127.5°. The Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectra (XPS) as well as X-ray diffraction (XRD) analysis results showed that KH550/KH590 and hexadecyl iodiele can be covalently bonded to the surface of SiC powder without altering its crystal configuration. This methodology may provide a new way of the modification of inorganic materials in further.

Dental Composites Based on Dimethacrylate Resins Reinforced by Nanoparticulate Silica

This paper describes morphological differences and associated functional properties of dental composites based on dimethacrylate resins reinforced by nanoparticulate silica filler modified according to different silanization procedures. Surface morphology of the materials was evaluated by means of AFM, while nanohardness and elasticity modulus of the surface layer - by nanoindentation and abrasion - gravimetrically. The effects of silane treatment of nanoparticulate silica surface on possible filler loading, mechanical properties and abrasion resistance of the composites were discussed. The influence of the amount and kind of silane coupling agent on the example of 3 -methacryloxypropyltrimethoxysilane and vinyltrimethoxysilane were presented. The modification of nanoparticulate silica with 3 -methacryloxypropyltrimethoxysilane enabled the introduction of 15% more filler than modification with vinyltrimethoxysilane. The abrasion resistance depended strongly on the composite morphology and the micromechanical parameters of the surface layer. The composite modified with vinyltrimethoxysilane, containing the highest percentage of filler particles smaller than 1 μm in diameter, exhibited the lowest abrasion (0.3 vol.%). Abrasive wear seemed to be a linear function of nanoindentation hardness with the correlation coefficient of R2 = 0.96. The highest hardness of the surface layer of commercial composite (130 MPa) resulted in the highest abrasive wear (7.7 vol.%). The type and the quantity of silane coupling agent used for silica modification strongly influence the morphology and mechanical and tribological properties of the dental composites. The application of more than the calculated, optimal amount of silane to nanosilica modification enables higher filler loading, but the composites exhibit inferior mechanical characteristics. Nanoindentation hardness of surface layer showed to be the most useful parameter in estimation of material susceptibility to abrasion.