Amount Of Silane Coupling Agent Research Articles

Minimizing usage of silane coupling agent for amine-grafted mesoporous silica CO2 adsorbent

AbstractAmine-grafted adsorbents are promising CO2 adsorbents; however, the excessive addition of an amino silane coupling agent during their synthesis increases their production cost. Thus, using low amounts of silane, we synthesized 3-aminopropyltrimethoxysilane (APTMS)-grafted SBA-15 mesoporous silica and evaluated its CO2 adsorption performance. APTMS-grafted SBA-15 samples were prepared using either impregnation or heating–filtration method (grafting). The obtained samples were characterized by X-ray diffraction spectroscopy, transmission electron microscopy, N2 adsorption/desorption, scanning electron microscopy, magic-angle spinning nuclear magnetic resonance, and elemental analysis. The results revealed that the micropores of SBA-15 were preferentially blocked, and APTMS increasingly occupied the mesopores with increasing amine loading. The CO2-adsorption performance of the adsorbents was measured by thermogravimetric analysis under dry conditions. Both synthesis methods achieved high amine immobilization efficiency (78.3–92.2%), as estimated from the amount of silane coupling agents used in the synthesis and that immobilized on the support. The adsorbents prepared by the two methods adsorbed similar amounts of CO2 of approximately 0.5 mmol g− 1 in 400 ppm CO2 and ~ 1.0 mmol g− 1 in 5 vol% CO2. The adsorption amounts attained in this study are comparable to those of previously reported silane-coupling-agent-modified adsorbents that were prepared with more silane. In contrast, the adsorption rate of the samples was affected by the synthesis method, even with similar amine loadings. Nonetheless, the results revealed that even with a low amount of the silane coupling agent, high-performance amine-grafted CO2 adsorbents could be synthesized.

Rubber-glass nanocomposites fabricated using mixed emulsions

Many composites consist of matrices of elastomers and nanoparticles of stiff materials. Such composites often have superior properties and are widely used. Embedding elastomers with nanoparticles commonly necessitates intense shear, using machines like extruders and roll millers, which cut polymer chains and degrade properties. Here, we prepare a rubber-glass nanocomposite by using two aqueous emulsions. Each emulsion is separately prepared with a single species of polymer chains. Each polymer chain is copolymerized with a small amount of silane coupling agent. Upon mixing the two emulsions, as water evaporates, the glassy particles retain the shape, and the rubbery particles change shape to form a continuous matrix. Subsequently, the silane coupling agent condensates, which cross-links the rubbery chains and interlinks the rubbery chains to the glassy particles. The cross-links and interlinks stabilize the nanostructure and lead to superior properties. The nanocomposite simultaneously achieves high modulus (~30 MPa), high toughness (~100 kJ m-2), and high fatigue threshold (~1,000 J m-2). The method of mixed emulsion is environmentally friendly and compatible with various open-air manufacturing processes, such as coat, cast, spray, print, and brush. Additionally, the silane coupling agent can interlink the nanocomposite to other materials. The method of mixed emulsion can be used to fabricate objects of complex shapes, fine features, and prescribed spatial variations of compositions.

Regulating surface energy and establishing covalent bonds to enhance interface interaction between m‐BN and polyphenylene oxide for 5G applications

AbstractIncorporation of boron nitride (BN) into polymers is a promising method to obtain composites with high thermal conductivity, low dielectric constant (Dk), and dielectric loss (Df), while the practical applications are limited by the poor interface between BN and polymer because of surface energy mismatch and absence of covalent bond connection between them. Herein, polydopamine (PDA) with good adhesion is deposited onto the BN. Then, a different amount of silane coupling agent containing vinyl reactive groups is grafted onto PDA‐coated BN. In this way, the surface energy of modified BN (m‐BN) can be adjusted to ensure BN contacts well with polymers. Moreover, reactive groups were introduced on BN for further reaction. Subsequently, covalent bonds between the m‐BN and the polyphenylene oxide (PPO) were established in situ during the curing process. The effects of the m‐BN surface energy on interface quality and thermal conductivity of composites are investigated. The m‐BN/PPO composite achieves a through‐plane thermal conductivity of 5.87 W/m·K and a low Df value of 1.53 × 10−3, as well as a low coefficient of thermal expansion (CTE) value (7.8 ppm/K) when the m‐BN loading is 32.6 vol%. This research provides a simple and efficient strategy for fabricating high‐performance composites for high‐frequency applications.Highlights Hexagonal boron nitride was modified successfully by combining non‐covalent and covalent modifications. Regulating surface energy and establishing covalent bonds enhances interface interaction between BN and polyphenylene oxide. Modified BN/polyphenylene oxide composites display improvements in thermal conductivity and dimensional stability as well as dielectric loss. Provides a feasible strategy for designing polymer composites with high thermal conductivity, dimensional stability, and low dielectric loss for 5G applications.

MACRO- AND MICRO-DISPERSION OF SILICA IN TIRE TREAD COMPOUNDS: ARE THEY RELATED?

ABSTRACT The dispersion of rubber fillers, such as silica, can be divided into two categories: macro- and micro-dispersion. Both dispersions are important; however, to achieve the best reinforcement of rubber, micro-dispersion of silica is crucial. The common view is that these filler dispersions are strongly related. The micro-dispersion is understood as the consequence of the continuous breakdown of filler clusters from macro-dispersion. Yet, a large problem is that an objective unequivocal direct measurement method for micro-dispersion is not available. In this study, a set of parameters is defined that are anticipated to have an influence on the micro- as well as the macro-dispersion. Mixing trials are performed with varying silanization temperature and time, different amounts of silane coupling agent, and by using silicas with different structures and specific surface areas. The degrees of micro- and macro-dispersion are evaluated by measuring the Payne effect as an indirect method for micro-dispersion and using a dispergrader for quantitative measurement of macro-dispersion. The results show that the filler dispersion processes happen simultaneously but independently. These results are supported by earlier work of Blume and Uhrlandt, who stated as well that micro- and macro-dispersion are independent. The major influencing factors on micro- and macro-dispersion of silica are also identified.

Preparation and characterization of attapulgite microcapsules coated with acrylic polymer

The attapulgite core-shell microcapsule type flame retardant was prepared by in situ polymerization. Attapulgite (ATP) was used as a core material with poly(methyl methacrylate) (PMMA) and poly(methyl methacrylate-co-acrylic acid) [P(MMA-co-AA)] as shell materials. The attapulgite was modified by the silane coupling agent. The effects of different shell materials and modification methods on the structure and properties of attapulgite core-shell microcapsules were studied by scanning electron microscopy, particle size distribution, infrared analysis and thermogravimetric analysis. The results showed that the coating effect was best when the amount of silane coupling agent was 1% of the attapulgite mass. The particle size of the microcapsule prepared with PMMA as shell material was uniform and the coating efficiency was better. After the copolymerization of acrylic acid (AA) in MMA shell materials, the cladding efficiency was improved. At the same time, the thermal decomposition temperature of the microcapsule shell material was greatly reduced, which is beneficial to the performance of attapulgite flame retardant.

Long-term performance of silane coupling agent/metakaolin based geopolymer

This article reports the effects of different dosages of silane coupling agent (KH-550) on the properties of geopolymer that have been cured for 360 days. The mineral phase formation and microstructure changes of geopolymer were analyzed combined with mechanical properties, XRD, FT-IR, SEM and 29Si NMR. The results show that adding an appropriate amount of silane coupling agent can improve the toughness of geopolymer, and the best performance is obtained when the silane coupling agent content is 0.1 wt%. The highest compressive strength and flexural strength of geopolymer samples containing 0.1 wt% silane coupling agent cured for 90 days reached 51.4 MPa and 12.93 MPa, respectively. The gel phase in the geopolymer is significantly enriched after adding silane coupling agent. Combined with 29Si NMR analysis, it can be seen that the doping of silane coupling agent promotes the polymerization reaction, and gradually develops towards low-aluminum bonded silica and Q4(0Al) structure. The decrease in Q4(0Al) structure of the geopolymer samples cured for 360 days indicates the weakening of the geopolymerization reaction and also explains the decrease in strength after long-term curing.

The NOx Degradation Performance of Nano-TiO2 Coating for Asphalt Pavement.

The NOx degradation performance of nano-TiO2 as a coating material for the road environment was evaluated in this research. The nano-TiO2 coating materials for both road surface and roadside were prepared by using anatase nano-TiO2, activated carbon powder, silane coupling agent and deionized water. The impact of varying amounts of coating material and silane coupling agent were evaluated. The road environment of NOx degradation was simulated by the photocatalytic test system designed by the research team. For the road surface coating, the photocatalytic degradation experiments of NO under different radiation intensities were carried out. The results show that the material has good photocatalytic degradation performance, and the proper amount of silane coupling agent can enhance the bonding performance of the material and asphalt mixture. For the roadside coating, sodium dodecylbenzene sulfonate was selected as the surfactant to carry out the photocatalytic degradation experiment of NO2 with different dosages of surfactant. The results showed that when the mass ratio of nano-TiO2 and surfactant was about 1:2, the catalytic degradation effect of the material was the best.

Fabrication and characterization of highly hydrophobic rutile TiO2-based coatings for self-cleaning

Highly hydrophobic rutile TiO2 nanocomposites modified by silica (SiO2) and silane coupling agent KH570 were synthesized. The chemical structure and morphology of TiO2 nanopowders before and after modification were investigated by Brunauer-Emmett-Teller, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and transmission electron microscope techniques. The results revealed that a continuous and dense SiO2 coating layers was formed on TiO2 surfaces via Si–O–Ti bonds first, acting as a barrier that separates TiO2 particles from the medium. Then after modification by KH570, the composite powder had obvious hydrophobic property. The amount of silane coupling agent had an important influence on the achieved properties. TiO2@SiO2 nanocomposites modified with 0.3 ml KH570 exhibited the best excellent hydrophobicity with water contact angle of 141°, highlighting its potential application as a pigment in exterior wall coatings.

Physicochemical Properties of Bis-GMA/TEGDMA Dental Resin Reinforced with Silanized Multi-Walled Carbon Nanotubes

The multi-walled carbon nanotubes (CNTs) modified by different amount of silane coupling agents named 3-(methacryloxy)propyltrimethoxysilane (γ-MPS), were incorporated into dental resin matrix in a series of mass ratio, with the aim to enhance the mechanical properties of dental resin matrix. The double bond conversion (DC) of dental resin matrix was investigated with a FT-IR instrument. Water sorption (WS) and solubility (SL) were obtained until the mass variation of dental resin matrix in distilled water kept stable. Flexural strength (FS) and modulus (FM) of dental resin matrix were measured using a three-point bending set up in a Universal testing machine. The fracture surfaces of specimens were observed with a scanning electron microscope. The results showed that all of CNTs containing dental resin matrix had lower DC (p < 0.05) than control resin matrix. Only adding 0.025 wt.% multi-walled carbon nanotubes (modified with 1.0 wt.% of γ-MPS) into dental resin matrix could enhance the FS and FM of dental resin matrix, as well as reducing the WS and SL of dental resin matrix. Therefore, the best properties of dental resin matrix could be obtained by incorporating 0.025 wt.% of CNTs, which were modified by 1.0 wt.% of silane coupling agents.

Distribution Control-Oriented Intercalation of a Cationic Metal Complex into Layered Silicates Modified with Organosulfonic-Acid Moieties.

A layered sodium silicate, octosilicate (Na2Si8O17· nH2O), was modified with an organosulfonic-acid moiety (sulfonated propyl (SPr) group, sulfonated phenethyl (SPhE) group, or sulfonated p-trifluoromethylphenyl (STFPh) group) for use as a host material to accommodate a cationic guest, tris(2,2'-bipyridine)ruthenium(II) cation ([Ru(bpy)3]2+). The organosulfonic-acid moiety was bound to the silicate layer via a reaction of an alkylammonium-exchanged octosilicate with a silane coupling agent, and subsequent treatment (oxidation or sulfonation) of the bound organosilyl groups; the surface densities of the organosulfonic-acid moiety were varied by controlling the added amount of silane coupling agents. Adsorption of [Ru(bpy)3]2+ onto surface-modified octosilicates was conducted to find that some surface-modified octosilicates successfully adsorbed [Ru(bpy)3]2+ in the interlayer space (intercalation), while other surface-modified octosiliates did not. In addition, the UV-vis absorption and the luminescence indicate that intercalated [Ru(bpy)3]2+ diffused in the interlayer and that the distribution of the time-averaged location varied depending on the kind and amount of the organosulfonic-acid moieties. Thus, the kind and surface density of the organosulfonic-acid moiety, which correlates to the interactions between the group and the guest species, the volume of free nanospace for adsorption and motion of guests, and the swelling properties, are the key factors not only for the intercalation ability but also for the dynamics of the guest in the interlayer space.

Mixing and Comparative Properties of NR Compounds Filled with Different Types of Reinforcing Fillers

Mixing behaviors of the compounds filled with different reinforcing fillers were studied in correlation with compound and vulcanizate properties. Four filler systems were used including: 1) silica plus small amount of silane coupling agent; 2) carbon black; 3) pre-modified silica; and 4) silica+silane-carbon black mixed one. The results have shown that silica provides longer optimum cure time and shorter cure rate than carbon black due to accelerator adsorption on silica surface. In addition, owing to highly polar nature on silica surface the silica-based compounds show rather high viscosity, attributed to stronger filler-filler interaction as can be confirmed by Payne effect and reinforcement index. However, the commercial surface treatment or pre-modified form of silica shows superior properties than in-situ modification of silica by silane during mixing, while it gives comparable properties to carbon black-based compound. Tensile properties of vulcanizates show a good correlation with the basic properties of their compounds.

Effects of surface modification of silane coupling agent on the properties of concrete with freeze-thaw damage

Surface waterproofing treatment with silane coupling agent is developed to prepare surface modification concrete, in recent years, which possesses an excellent permeability resistance. Freeze-thaw damage inevitable exists in concrete exposed to the cold environment, therefor this paper intensively investigates the effects of surface modification of silane coupling agent on the properties of concrete with freeze-thaw damage. Freeze-thaw cycles, capillary absorption, chloride penetration and carbonization tests were carried out, respectively. The results demonstrate that the surface waterproofing treatment is appropriate for the durability repairing of concrete with freeze-thaw damage, and the penetration depth of silane coupling agent in concrete increases linearly with the rise of freeze-thaw damage. The water and chloride permeability both increase with the increased freeze-thaw cycles for various concrete; however, the surface modification concrete has a better permeability resistance than ordinary concrete with the same freeze-thaw damage. In particular, the permeability resistance increases with the increases of applied amount of silane coupling agent, and there exists a good correlation between the permeability behavior and induced freeze-thaw damage for various concrete. Abrasion significantly decrease the permeability resistance of surface modification concrete, which should be considered carefully in the durability repairing.

Performance of Granite Asphalt Mixture Modified by Silane Coupling Agent

In order to improve pavement performance of granite asphalt mixture, the surface of granite mineral powder was organic modified by silane coupling agent. The water stability and high temperature stability of the asphalt mixture were analyzed by Marshall tests, immersion Marshall test, freeze-thaw splitting test and rutting test. The results show that the mixing amount of silane coupling agent in the range from 0.5% to 2.5% can significantly improve the high temperature stability and water stability of the asphalt mixture. Taking into account the performance and economic factors, 2.0% silane coupling agent on the surface of granite filler was recommended.

Particle morphology dependent superhydrophobicity in treated diatomaceous earth/polystyrene coatings

Superhydrophobic surfaces have been prepared from three different types of diatomaceous earth (DE) particles treated with 3-(heptafluoroisopropoxy)propyltrimethoxysilane (HFIP-TMS) and low molecular mass polystyrene. The untreated particles, consisting of CelTix DE (disk shape), DiaFil DE (rod shape) and EcoFlat DE (irregular), were studied using particle size analysis, bulk density, pore volume and surface area analysis (via Brunauer–Emmett–Teller, BET, methods). The treated particles were characterized with thermogravimetric analysis (TGA), contact angles, scanning electron microscopy, profilometry, and FTIR spectroscopy. The minimum amount of silane coupling agent on the DE surfaces required to obtain superhydrophobicity of the particles was determined and found to be dependent on the particle morphology. In the coatings made from different particles with 2.4wt% HFIP-TMS, the minimum amounts of treated particles (loadings) for superhydrophobicity was determined with the less dense CelTix DE requiring about 30wt%, DiaFil DE requiring about 40wt%, and EcoFlat DE each requiring about 60wt% loading of treated particles.

High temperature and pressurized steaming/silane coupling co-modification for wood fibers and its effect on the properties of wood fiber/HDPE composites

Poplar fibers were pretreated under high temperature and pressurized steam at different temperatures and pressures; they were further modified using different amounts of silane coupling agent. The obtained modified fibers were used to prepare wood fiber/high-density polyethylene (HDPE) composites by an extrusion-molding process. The effects of high temperature and pressurized steaming/silane coupling co-modification on the properties of wood fiber/HDPE composites were investigated. The results show that after the high temperature and pressurized steaming treatment, the amount of hydroxyl groups on the surface of the fibers and surface polarity of the fibers decreased, whereas the crystallinity and thermal stability significantly increased. The storage modulus and mechanical properties of the composites improved as well. The addition of silane to the steam-treated fibers further enhanced the storage modulus, loss modulus, and the mechanical properties of the composites. Moreover, when the wood fibers were only modified by adding silane and the silane content was 5%, the prepared composites showed better mechanical properties than the high temperature and pressurized steaming treatment. However, the addition of a small amount of silane to the wood fibers exposed to steam at 170 °C and 0.8 MPa provided even better results; when 2% silane was added, the composites showed the best mechanical properties.

Dispersion and filler network structure of fibrillar silicates in elastomers

The dispersion and filler network of fibrillar silicate (FS) in elastomers were studied. The results showed that a good dispersion of FS in matrix during mechanical blending in unvulcanized composites contributed to a strong FS filler network, different from that of traditional reinforcing fillers. Meanwhile, the filler re-aggregation during vulcanization caused by the overlapping and intertwining of FS further strengthened the filler network. The factors including Mooney viscosity and molecular polarity of elastomer, type and amount of silane coupling agents used for filler modification, that may influence the filler network, were studied. Our study helps us to understand the mechanism for the formation of filler network of FS in elastomers and provides guidance for the preparation of high performance FS/elastomer composites.

Effect of surface treatment of nanoclay on the mechanical properties of epoxy/glass fiber/clay nanocomposites

A new method of silane treatment of nanoclays is reported where in the clay is nanodispersed in hydrolyzed silanes. The surface functionalization of Cloisite® 15A nanoclay has been carried out using two different silane coupling agents: 3-aminopropyltriethoxy silane and 3-glycidyloxypropyltrimethoxy silane using varied amounts of silane coupling agents, e.g. 10, 50, 200, and 400 wt% of clay. The surface modification of Cloisite® 15A has been confirmed by Fourier transform infrared spectroscopy. The modified clays were then dispersed in epoxy resin, and glass fiber-reinforced epoxy clay laminates were manufactured using vacuum bagging technique. The fiber-reinforced epoxy clay nanocomposites containing silane modified clays have been characterized using small angle X-ray scattering, transmission electron spectroscopy and differential scanning calorimetry. The results indicate that the silane treatment of nanoclay aided the exfoliation of nanoclay and also led to an increase in mechanical properties. The optimized amount of silane coupling agents was 200 wt%. The nanocomposites containing clay modified in 200 wt% of silanes exhibited an exfoliated morphology, improved tensile strength, flexural modulus, and flexural strength. The improved interfacial bonding between silane modified nanoclays and epoxy matrix was also evident from significant increase in elongation at break.

Tailoring of thermal and dielectric properties of LDPE-matrix composites by the volume fraction, density, and surface modification of hollow glass microsphere filler

Hollow glass microsphere (HGM) filled low-density polyethylene (LDPE) composites were prepared, and the effects of density, content, and surface modification of HGM on the thermal and dielectric properties of the composites were investigated. It is found that the thermal conductivity of the composites decreases with increasing HGM content or decreasing HGM density. At the same HGM content and density, the composites filled with suitable amount of silane coupling agent (KH570) modified HGM exhibit higher thermal conductivity than unmodified-HGM filled composites. The dielectric constant at 1MHz of the composites also decreases with increasing HGM content or decreasing HGM density, but their dielectric loss increases with increasing HGM content or increasing HGM density. By modifying the surface of HGM with suitable amount of KH570, the dielectric constant and loss at 1MHz of the composites can be decreased at the same time. The results of microwave dielectric properties of the composites indicate that the dielectric constant decreases with increasing HGM content or decreasing HGM density, the quality factor (Q×f) decreases with increasing HGM content or increasing HGM density, but both dielectric constant and quality factor are slightly affected by the surface modification of HGM. Due to lower intrinsic thermal conductivity and dielectric constant but higher dielectric loss of HGM than LDPE, the thermal conductivity and dielectric properties of the composites can be controlled with adding HGM and varying its volume fraction. The surface modification of HGM improves the interface contact between HGM and LDPE in the composites, which is confirmed by the SEM observation, and thus the heat conduction and dielectric properties at low frequency are improved. Based on calculated thermal conductivity and dielectric constant of HGM, the experimental trends of thermal conductivity and dielectric constant at 1MHz of the composites are analyzed by using different models, including typical models for particles-filled composites and special models developed for hollow microsphere filled composites. The results from suitable models show close correlation with the experimental values.

Investigation of Interaction between the Silicone Rubber Sealant and Concrete Substrate

Abstract This investigation aimed to study the interaction between concrete substrate and silicone rubber sealant. Several surface treatments were applied in order to obtain different levels of surface roughness in concrete substrates. The bond tensile test showed that abrasion and solvent cleaning methods improved the bond strength relative to that of untreated substrates. The effects of silane coupling agents on the bond strength was studied via two methods of application of the coupling agent, namely, (a) pre-treatment of concrete substrate in an aqueous solution of silane, and (b) adding silane to the silicone rubber sealant as an integral blend additive. No significant differences in bonding values were noted between the two methods. An increase in the amount of silane coupling agent increased the bond strength of the silicone rubber sealant, but beyond a certain point, further increases in the amount of silane lowered the bond strength. As the amount of silanes increased, the failure mode of the samples changed from adhesive failure to cohesive failure. Scanning electron microscopy and contact angle methods were employed to investigate the interface. The results strongly suggest that interface adhesion and treatments are crucial factors in creating a durable bond interface between substrate and sealant.

Adhesion enhancement of ink-jet printed conductive copper patterns on a flexible substrate

Ink-jet printed conductive copper patterns with enhanced substrate adhesion were fabricated using a conductive copper ink containing a silane coupling agent as an adhesion promoter. The effect of the silane coupling agent on the copper complex ion ink properties, including viscosity and surface tension, was systematically investigated. The copper complex ion ink that was ink-jet printed on a polyimide film was transformed to copper films by thermal treatment at 200 °C for 2 h in H2. The phase, microstructure, resistivity and peel strength were examined by X-ray diffraction, field emission scanning electron microscopy, the four-point probe technique, the 90° peel test and the ASTM D3359 tape test. The proper amount of silane coupling agent was determined according to the electrical conductivities and adhesive strengths of the ink-jet printed copper patterns containing varied amounts of adhesion promoter. As a result, the patterns formed from copper complex ion ink containing 3 wt% silane coupling agent exhibited not only the highest peel strength (240.3 gf mm−1 and 4B) but also low resistivity (approx. 20 μΩ cm). The mechanism of adhesion promotion via the silane coupling agent was also suggested.