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The paper aims to provide a facile approach to the synthesis of polyurethane–silica nanocomposites by introducing self-made aqueous silica sols with different particle sizes into polyurethane materials. This paper investigates the effects of the silica nanoparticles on the polyester polyol, as well as the physical properties and transmittance of the hybrid polyurethane coatings.

Colloidal silica particles of different sizes were obtained using a sol–gel process and were then embedded into polyester polyol by in-situ polymerization. These polyester polyol–silica resins were synthesized using an azeotrope process, using xylene to remove the water generated in the system and present in the dispersion medium for the colloidal silica. The polyester polyol–silica resins were further cured using isocyanate trimers to form polyurethane–silica hybrid films.

The paper observed that the viscosity of the polyester polyol–silica nanocomposite resins increased and their appearance changed from transparent to ivory white as the particle size of the added silica was increased. It was found that increasing the hydroxyl content of the silica improved the film transmittance in the visible light region. However, the transmittance decreased sharply once the diameter of the silica particles reached 100 nm.

Because of the limitation of experimental conditions, some performances have not been tested. Therefore, researchers are encouraged to conduct further tests.

The paper provides a method of preparing hybrid polyurethane film by using silica; the results indicate that the introduction of nano-silica can improve the wear resistance and glass transition temperature of polyurethane coatings.

The results obtained in this study will be extremely useful to enhance the understanding of organic–inorganic hybrid materials.

The purpose of this paper is to study methods of reacting the surface of the particles of silica sols with silanes, primarily gamma‐glycidoxypropyltrimethoxysilane (GPTMS) and study some basic properties of the modified sols and the nature and structure of the silane groups attached to the particle surface.

The surface of the silica particles was modified by reacting the silica sols with aqueous solutions of silanes, chiefly GPTMS. The presence and structure of silane groups on the particle surface were established by Si‐NMR and C‐NMR, respectively.

Several silanes were studied but silica sols could be readily modified only with GPTMS and glycidoxypropylmethoxydiethoxysilane (GPMDES), most readily if the silanes were pre‐hydrolysed in water. Higher degrees of silylation were preferably done by continuous addition of silane. Lower degrees of modification can be achieved at room temperature by the stepwise addition of the silane solution. The silylation of the silica surface with GPTMS significantly reduces the number of charged surface groups and silanol groups. GPTMS binds covalently to the silica surface and the epoxy ring opens and transforms into a diol. Silica sols modified with GPTMS and GPMDES are stable toward aggregation.

Only organo‐reactive silanes were studied.

This is the first work to study the modification by silanes of silica aquasols with high concentrations of silica. The silane modification can extend the use of silica to areas of applications previously inaccessible to silica sols.

The purpose of this paper is to prepare stabile emulsions with 0–15% of colloidal silica and high monomer/water ratio and to investigate the influence of silica addition and surface modification on the polyacrylate properties.

Improving the properties of the composite can be achieved by optimizing the compatibility between the phases of the composite system with improving the interactions at the matrix/filler interface. Therefore, the silica surface was modified with nonionic emulsifier octylphenol ethoxylate, cationic initiator 2,2'-azobis-(amidinopropane dihydrochloride) and 3-methacryloxypropyltrimethoxysilane and polyacrylate/silica nanocomposites were prepared via in situ emulsion polymerization. Particle size distribution, rheological properties of the emulsions and morphology, thermal properties and mechanical properties of the film prepared from the emulsions were investigated.

Polyacrylate/silica systems with unmodified silica, silica modified with nonionic emulsifier and cationic initiator have micrometer, while pure PA matrix and systems with silica modified with silane have nanometer particle sizes. Addition and surface modification of the filler increased emulsion viscosity. Agglomeration of silica particles in composites was reduced with silica surface modification. Silica filler improves thermal stability and tensile strength of polyacrylate.

This paper provides broad spectrum of information depending on filler surface modification and latex preparation via in situ emulsion polymerization and properties with high amount of filler and monomer/water ratio with the aim that prepared latex is suitable for film formation and final application.

Despite recessionary years in 1990 and 1991, West European demand for specialty silicas has increased at an average annual rate of 8% per year over the past five years as detailed in a new study from Kline and Company. In 1991, total European demand reached $425 million for the eight silica products listed in Table 1. These silicas, which include both synthetically manufactured products as well as natural minerals, are used in a wide variety of industrial and consumer applications. Specialty silicas impart such unique functions as reinforcement, thickening or electrical properties to these applications and are not used merely as cost reducing fillers.

The purpose of this paper is devoted to application of the emulsion polymer of poly(methyl methacrylate-co-butyl acrylate) prepared with in situ nano-silica as a novel tanning agent of hide to partly or totally replace chrome salt and to improve physical, thermal and mechanical properties of the tanned leather and to reduce the environmental impact of chrome tanning effluent.

Polymer/nano-silica hybrid emulsions were prepared via in situ seed emulsion polymerisation. The prepared polymers were characterised for solid content, molecular weight, viscosity, drying time, minimum film-forming temperature (MFFT) and microstructures (via transmission electron microscopy). The mechanical, thermal and surface morphological (by scanning electron microscope) properties of the treated samples were also investigated. The influences of the increase in the content of organic nano-silica on the properties of the tanned leather are discussed.

It was found that the viscosity, the particle size and the solid content of the prepared polymers increased as the content of the nano-silica increased while gloss and drying time of the resulting polymer film decreased. Tanning buffalo hide by Polymer F (containing a high content of nano-silica) gave desirable properties in terms of tensile strength, thermal stability and shrinkage temperature.

This paper discusses the preparation and the characterisation of emulsion polymers with in situ nano-silica and their application in tanning process to enhance and improve the leather quality, as well as reduce the use of chrome tanning materials and consequently chrome tanning waste.

The tanned leather showed an improvement of physico-mechanical properties and enhancement of thermal stability. Furthermore, the tanned leather has uniform colour, softness and firmness of grain. All these promising results provide evidence to support the applicability of the prepared co-polymer/nano-silica emulsions as an efficient tanning agent that also provides lubricating properties for leather.

Since May 2015, REACH Annex XVII restricts Cr(VI) in leather articles or leather parts of articles that come into contact with skin to a concentration of less than 3 mg/kg. Cases of discovery of Cr(VI) in leather papers have been reported by the European rapid alert system on dangerous consumer products (RAPEX). The emulsion poly (methyl methacrylate-co-butyl acrylate) with in situ nano-silica that has been developed via the study reported in this paper is one of the better technologies for the reduction of chromium ratio used in tanning industry.

The purpose of this paper is to investigate epoxysilane‐modified silica sols as surfactant‐free inorganic pigments dispersants and as co‐binders/reinforcing agents for silicate paints.

The performance of epoxysilane‐modified silica sols as dispersants for titania was studied using a polyacrylate‐based dispersant as reference. Furthermore, the effect of the addition of silica sols, with or without silane modification, to potassium silicate on binder properties was investigated.

Significant improvements were obtained in stability towards settling in water‐based titania pigments pastes and in light‐scattering efficiency (as much as 50 per cent) for the optimal size of the silica particle of 5 nm. The number of silane molecules per nm² silica particle surface must exceed a critical value of at least 1 molecule of epoxysilane per nm² particle surface. Additionally, improved stability towards gelling, water resistance and film‐forming properties of sol‐silicate binder mixes were achieved for epoxysilane‐modified silica sols.

Only epoxysilane‐modified silica sols were studied in this report. Titania pigment was examined but other important pigments (e.g. iron oxides) remain to be studied. In addition, only sol‐silicate mixes were investigated and not fully formulated silicate paints.

A method that produces stable, high‐performing, surfactant‐free inorganic pigments pastes. Furthermore, stable, high‐ratio, sol‐silicate binders can be obtained with improved water resistance and film properties for use in silicate paints.

The present method provides an easy route to obtain stable surfactant‐free inorganic pigments pastes, as well as makes stable, high‐ratio, sol‐silicate mixes/paints.

Steam contamination (solid particles in the superheated steam) comes from the boiler water largely in the carry‐over of water droplets. The need for extreme purity of steam for use in high pressure turbines has prompted the development of highly satisfactory devices for separating steam and water in a boiler drum. Consequently, steam contamination has been steadily reduced. Troublesome turbine blade deposits may occur with surprisingly low (0.6 ppm) total solids contamination in steam. In the 3.5–6 MPa range, however these deposits are usually water soluble and can be removed by periodic washing. In the 4 to 10 MPa range, however, silica deposits predominate and these deposits are not easily removed by water washing. With operating pressure of 13 MPa and above insoluble deposits do occur which may be controlled by residual water washing. Before the unit is returned to service, the deposits should be removed by air or water‐driven turbine cleaners or by chemical cleaning.

The purpose of this paper is to characterise the electrokinetic properties of pigments supported on both unmodified and modified silica. The paper describes the preparation of hybrid pigments via adsorption of organic dyes on silica supports and determination of the zeta potential and electrophoretic mobility of the materials obtained.

The materials studied were hybrid pigments obtained as a result of adsorption of two basic dyes: C.I. Basic Red 1 and C.I. Basic Orange 14 and one acidic dye C.I. Mordant Red 3 from solutions of concentrations of 500, 2,000 and 3,000 mg/dm³ on the surface of both unmodified and modified silica supports. The agent used for modification of the silica surface was N‐2‐(aminoethyl)‐3‐aminopropyltrimethoxysilane.

The modification of the silica surface with aminosilane was found to change, significantly, the electrokinetic character of the inorganic support. This change was interpreted as being due to the ionisation of −NH₂ groups from the modifier molecule, which changes the surface charge. Electrokinetic curves of the pigment composites changed considerably as a function of the type and concentration of the organic dye adsorbed.

Only SiO2 supports (unmodified and aminosilane‐grafted) and C.I. Basic Red 1, C.I. Basic Orange 14 or C.I. Mordant Red 3 dyes adsorbed on its surface were evaluated. Other dyes could also be studied.

Measurements of the zeta potential were used to characterise the stability of colloidal dispersions of paints or dyes and to control the stability of paints on storage and their performance on painting and drying.

The paper demonstrates that the measurements of zeta potential permit determination of the optimum conditions for the use of a given pigment. The finding of the change of the zeta potential of a given pigment and so, also its application properties as a result of different functional groups in the dye or the modifying agent molecules.

The purpose of this paper is to develop methods to produce white composite pigments consisting of a silica core with a titania shell.

Silica cores were coated with titanium dioxide (TiO₂) via forced hydrolysis of a solution prepared from titanium tetrachloride (TiCl₄). The morphology, surface charge and particle size of obtained composite particles were studied.

Dispersions of well‐dispersed composite particles, having silica cores of uniform size in the range from 300 to 500 nm with a homogeneous titania coating are obtained. The coating thickness corresponded to 150‐400 per cent by weight of titania based on the core. Modification of the silica core by incorporation of 1.5 aluminosilicate sites per square nanometre of core surface proves to be favourable in achieving a homogeneous coating on the silica core. Deposition of such titania coating is also favoured by agitating the dispersion well, keeping electrolyte content low, maintaining pH at 2.0 and the temperature at 75°C during the coating process.

Only TiCl₄ is used as titania source. In addition, only silica cores obtained by Stöber synthesis are used while commercially available silica solutions made from sodium silicate are not used.

The process offers a method of producing a white composite pigment with a narrow particle size distribution in order to maximise light scattering as well as using a core with lower density than the shell. This kind of particle would be of interest for coating applications and white inorganic inks.

The developed method provides a straightforward process to produce well‐defined composite particles.

This study aims to perform the surface treatment of synthetic α-Fe₂O₃ red iron oxide pigment with hydrolysate 3-aminopropyl silane (A) and colloidal silica (CS) and investigate the effects of surface-treated pigment on the styrene acrylic (SA) emulsion and polyurethane (PU) dispersion.

For this purpose, firstly red iron oxide particles were modified with A and CS separately in an aqueous medium. After isolation of the modified iron oxide were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS). Moreover, the degree of the dispersion stability of the modified pigment in coatings with SA emulsion and PU dispersion was investigated by using an oscillation rheometer. Loss (G''), storage (G') modulus, loss factor [tan(δ)] and yield stress (τ⁰) values were determined by performing amplitude and frequency sweep tests.

The τ⁰ in SA coatings decreases with the amount of used A and increases with the amount of used CS. The τ⁰ decreases as the amount of used A and CS in PU coatings increases. The use of CS on red iron oxide pigments causes storage modulus to increase in SA coatings at low angular frequencies, while it causes a decrease in PU coatings.

To the best of the authors’ knowledge, for the first time, the suspended state of the iron oxide hybrid pigment formed with CS in the coating was investigated rheologically in this study.