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Article
Publication date: 12 August 2019

Junrui Zhang, Guojun Jiang, Tianhao Huang, Jun Xie and Da Shi

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…

Abstract

Purpose

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.

Design/methodology/approach

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.

Findings

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.

Research limitations/implications

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

Practical implications

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.

Originality/value

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

Details

Pigment & Resin Technology, vol. 48 no. 5
Type: Research Article
ISSN: 0369-9420

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Article
Publication date: 13 September 2011

Peter Greenwood and Borje Gevert

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…

Abstract

Purpose

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.

Design/methodology/approach

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.

Findings

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.

Research limitations/implications

Only organo‐reactive silanes were studied.

Originality/value

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.

Details

Pigment & Resin Technology, vol. 40 no. 5
Type: Research Article
ISSN: 0369-9420

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Article
Publication date: 16 June 2021

Zrinka Buhin Šturlić, Mirela Leskovac, Krunoslav Žižek and Sanja Lučić Blagojević

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…

Abstract

Purpose

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.

Design/methodology/approach

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.

Findings

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.

Originality/value

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.

Details

Pigment & Resin Technology, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 0369-9420

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Article
Publication date: 1 February 1993

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…

Abstract

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.

Details

Pigment & Resin Technology, vol. 22 no. 2
Type: Research Article
ISSN: 0369-9420

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Article
Publication date: 23 April 2020

Abd El-Wahab H., Farouk Abd El-Monem, Naser M.A., Hussain A.I., Elshhat H.A. Nashy and Lin L.

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…

Abstract

Purpose

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.

Design/methodology/approach

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.

Findings

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.

Research limitations/implications

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.

Practical implications

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.

Originality/value

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.

Details

Pigment & Resin Technology, vol. 49 no. 4
Type: Research Article
ISSN: 0369-9420

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Article
Publication date: 9 November 2010

Peter Greenwood

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…

Abstract

Purpose

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.

Design/methodology/approach

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.

Findings

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.

Research limitations/implications

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.

Practical implications

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.

Originality/value

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.

Details

Pigment & Resin Technology, vol. 39 no. 6
Type: Research Article
ISSN: 0369-9420

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Article
Publication date: 1 October 1988

P. Ghosh

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…

Abstract

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.

Details

Anti-Corrosion Methods and Materials, vol. 35 no. 10
Type: Research Article
ISSN: 0003-5599

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Article
Publication date: 6 January 2012

Teofil Jesionowski, Magdalena Nowacka and Filip Ciesielczyk

The purpose of this paper is to characterise the electrokinetic properties of pigments supported on both unmodified and modified silica. The paper describes the…

Abstract

Purpose

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.

Design/methodology/approach

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.

Findings

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.

Research limitations/implications

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.

Practical implications

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.

Originality/value

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.

Details

Pigment & Resin Technology, vol. 41 no. 1
Type: Research Article
ISSN: 0369-9420

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Article
Publication date: 25 May 2010

Peter Greenwood, Börje S. Gevert, Jan‐Erik Otterstedt, Gunnar Niklasson and William Vargas

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

Abstract

Purpose

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

Design/methodology/approach

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.

Findings

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.

Research limitations/implications

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.

Practical implications

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.

Originality/value

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

Details

Pigment & Resin Technology, vol. 39 no. 3
Type: Research Article
ISSN: 0369-9420

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Article
Publication date: 1 July 1982

Anne J. Walton

Thixotropy can be regarded as the loss of viscosity in a paint or other material that is brought about by mechanical agitation, and where the viscosity continues to…

Abstract

Thixotropy can be regarded as the loss of viscosity in a paint or other material that is brought about by mechanical agitation, and where the viscosity continues to decrease provided that this disturbance is continued for a period of time. Conversely, when the mechanical force is removed, the material then increases in viscosity and this recovery toward the initial structure continues to take place over a period of time. Sometimes the time dependency of the viscosity is vanishingly small so that the material is then properly referred to as pseudoplastic. In most of the literature, however, it is not usually possible to differentiate between thixotropy and true pseudoplasticity and therefore both kinds of structure are included in this review as they each are destroyed by mechanical agitation and recover when this is discontinued.

Details

Pigment & Resin Technology, vol. 11 no. 7
Type: Research Article
ISSN: 0369-9420

1 – 10 of 209