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1 – 10 of over 1000Abstract
Purpose
The purpose of this paper is to enhance the anticorrosion property of aluminium pigments and to improve their compatibility with polymers in coating.
Design/methodology/approach
Aluminium pigments encapsulated by organic‐inorganic layer were prepared by hydrolysis and condensation of organic silane acrylate resin and tetraethoxy silane (TEOS) on the surface of pigments via sol‐gel method. TEOS and poly (methyl methacryalte‐n‐butyl acrylate‐vinyl triethoxysilane) (PMBV) formed in advance by co‐polymerisation of methyl methacrylate (MMA), n‐butyl acrylate (BA) and vinyl triethoxysilane (VTES) were used as precursors. The adhesion property of the aluminium pigments was measured by peel test, and the loss of silvery appearance after encapsulation and acid soaking were both evaluated by colour lightness difference (ΔL) measurement. The encapsulated aluminium pigments were further characterised by means of FTIR, SEM, TG and XPS.
Findings
It was found that PMBV‐SiO2 thin films could be formed on the surface of aluminium pigments smoothly and uniformly, and the adhesion and anticorrosion performances of encapsulated aluminium pigments were improved significantly.
Research limitations/implications
The organic silane acrylate resin used as a precursor in the sol‐gel process could be synthesised from other aclyate monomers. In addition, the hydrolysis and condensation mechanism of organic silane acrylate resin on the surface of aluminium pigments need further studies.
Practical implications
The method developed provided a good solution to the two problems of aluminium pigments and increased their application values.
Originality/value
The method of improving adhesion and anticorrosion properties of aluminium pigments was novel and could find numerous applications in surface coatings and adhesives.
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Keywords
In part one the various properties of this important metallic pigment are considered.
Benjamin Tawiah, Liping Zhang, Anli Tian and Shai Shao Fu
The purpose of this paper is to colour aluminium pigment to the highest chroma using SiO2 and organic silane with dichlorotriazine reactive dye and investigate its reaction…
Abstract
Purpose
The purpose of this paper is to colour aluminium pigment to the highest chroma using SiO2 and organic silane with dichlorotriazine reactive dye and investigate its reaction mechanism, chemical stability and thermal properties to improve its applicability in surface coatings.
Design/methodology/approach
Aluminium pigment was encapsulated by the catalysed sol-gel method using SiO2, followed by modification with γ-glycidoxypropyltrimethoxysilane (GPTMS). Purified reactive dye (1-Amino-4-[3-(4,6-dichlorotriazin-2-ylamino)-4-sulfophenylamino]anthraquinone-2-sulfonic acid (X-BR)) was covalently immobilized onto modified SiO2 to obtain coloured aluminium pigment. The reaction mechanism, chemical stability and thermophysical properties were investigated by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscope, transmission electron microscope and thermogravimetric analyses (TGA).
Findings
The results showed that X-BR was covalently attached to modified Al/SiO2 with maximum colour grafting of 95 per cent when the dosage of GPTMS and X-BR per weight of modified Al/SiO2 was 25 and 15 per cent, respectively, at pH 8.5 and a temperature of 40°C. The coloured aluminium pigment had good chemical stability with excellent anti-migration properties in many solvents.
Research limitations/implications
The organic silane used required a careful control of pH to ensure maximum colour grafting efficiency meanwhile other silanes with amine groups could also be used effectively with different kinds of colorants besides reactive dyes.
Practical implications
The method used is less cumbersome and provides a simple route to preparing coloured aluminium pigment.
Originality/value
The use of organic-inorganic SiO2/γ- GPTMS with purified reactive dye to covalently colour aluminium pigment to the highest chroma is novel and will help advance the frontiers of knowledge on coloration of aluminium pigments.
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A severe problem with water‐borne paints containing aluminium or zinc pigments is hydrogen corrosion of these metals in the aqueous alkaline paint media. The subject of the…
Abstract
A severe problem with water‐borne paints containing aluminium or zinc pigments is hydrogen corrosion of these metals in the aqueous alkaline paint media. The subject of the present study is the examination of corrosion inhibition of aluminium and zinc pigments in aqueous alkaline media by different amino and polyamino acids. Aspartic acid inhibits this corrosion reaction of aluminium pigment only at pH 8 (protection factor 96 per cent) whereas polyaspartic acids do not. In contrast, aspartic acid stimulates the corrosion reaction of zinc pigment whereas polyaspartic acids show a moderate corrosion inhibiting effect. So, corrosion inhibition by aspartic and polyaspartic acids is completely different on aluminium and zinc pigment.
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Zhiling Ma, Yanjun Qiao, Fei Xie, Xianling Wang and Jing Wang
The purpose of this paper is to evaluate the role of encapsulation temperature on the preparation of silica-encapsulated waterborne aluminium pigments.
Abstract
Purpose
The purpose of this paper is to evaluate the role of encapsulation temperature on the preparation of silica-encapsulated waterborne aluminium pigments.
Design/methodology/approach
The waterborne aluminium pigments were prepared with H2O2 as anchoring agent and siloxane used as precursors in pH = 9.0 medium at different temperatures. The anchorage and compactness of silicon which on aluminium surface were characterized by optical microscopy, scanning electron microscopy and N2 adsorption-desorption. The anticorrosion property was characterized by the volume of produced hydrogen as a function of time.
Findings
The effect of encapsulation temperature on anticorrosion property of aluminium pigments is reflected from the anchorage and the compactness of silica on aluminium surface. Furthermore, when encapsulation temperature is 45-50°C, the silica platelets uniformly anchored on the aluminium surface as a dense film, which show the best anticorrosion property. Lower and higher encapsulation temperatures cause the silica platelets to agglomerate rather than anchor on the aluminium surface, which is unfavourable for the anchorage and the formation of compact silica film. The use of product in waterborne coatings gives a higher glossiness than that of raw material.
Research limitations/implications
Only pH = 9.0 medium was explored, and the other pH medium could result in different optimum temperatures.
Practical implications
The investigation results provide theoretical basis for obtaining excellent waterborne aluminium pigments.
Originality/value
The method of investigating corrosion resistance mechanism of aluminium pigments based on anchorage and compactness is novel.
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Zhiling Ma, Yajing Wen, Chunyan Zhang and Jing Wang
The purpose of this study is to evaluate the role of encapsulation pH and iron source on the anchorage mode and performance of iron oxide-encapsulated aluminium pigments.
Abstract
Purpose
The purpose of this study is to evaluate the role of encapsulation pH and iron source on the anchorage mode and performance of iron oxide-encapsulated aluminium pigments.
Design/methodology/approach
The coloured waterborne aluminium pigments were prepared at pH 5-7.5 by using FeSO4 and FeCl3 as iron source. The anchorage mode of iron oxides on aluminium was characterized using optical microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction. Furthermore, the pigmentary performance was characterized through anticorrosion test and multi-angle spectroscopy.
Findings
Diaspore and boehmite could form from H2O2 oxidizing aluminium. Both low pH and FeSO4 systems are beneficial for diaspore, inducing green rust anchor on the aluminium to form goethite. Either in FeSO4 or FeCl3 system, slightly high pH is beneficial for the formation of boehmite, which occurred together with ferrihydrite to form denser coating with yellowness and excellent anticorrosion property. At pH above 7, the formation of dendritic iron oxide is detrimental to the anticorrosion property and the glossiness.
Research limitations/implications
Only FeSO4·7H2O and FeCl3·6H2O as iron sources were explored.
Practical implications
The investigation results provide theoretical basis to obtain excellent chromatic waterborne aluminium pigments.
Originality/value
The method for investigation of encapsulation mechanism by surveying the structure of iron oxides on aluminium, which varies with the pH of the system and iron sources, is novel.
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The function of metallic pigments may be protective or decorative, sometimes both at the same time. The ultimate use of the pigments will determine the most suitable particle…
Abstract
The function of metallic pigments may be protective or decorative, sometimes both at the same time. The ultimate use of the pigments will determine the most suitable particle structure, whether the product is a paint or a plastic or an elastic composition. Protection may be provided against atmospheric or marine corrosion on the one hand, or against radiation — light or heat — on the other. In the former, metallic pigments of various particle structures are suitable, while in the latter the optical effect desired can only be obtained, as a rule, through the use of flaky or lamellar pigments. This is also the case when the metallic pigment is intended for decorative uses.
Bodo Müller and Sonja Kubitzki
Aluminium and zinc pigments react in aqueous alkaline media (e.g. water‐borne paints) by the evolution of hydrogen which can be measured gasvolumetrically. Certain organic…
Abstract
Aluminium and zinc pigments react in aqueous alkaline media (e.g. water‐borne paints) by the evolution of hydrogen which can be measured gasvolumetrically. Certain organic heterocycles are well‐known corrosion inhibitors for different metals. The six different heterocyclic compound which were examined inhibited the corrosion reaction of zinc pigment in aqueous alkaline media. The most efficient inhibitors were 1H‐benzotriazole at pH 8 and 10 and 2‐(5‐aminopentyl)benzimidazole only at pH 10. In contrast, with addition of all heterocycles there was no corrosion inhibition on aluminium pigment. This complete difference in the corrosion inhibiting effect of the heterocycles with respect to the two different metal pigments can be explained with Pearson’s “Principle of Hard and Soft Acids and Bases”.
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There are many pigment grades varying in manufacturing processes and product specifications. However, the most common denominator for which prices can be compared is the covering…
Abstract
There are many pigment grades varying in manufacturing processes and product specifications. However, the most common denominator for which prices can be compared is the covering power or specific surface area of pigments. Pigments with higher surface area command a higher price, reflecting a longer milling time and increased production and labour costs.
The paper deals with studying the anticorrosive properties of condensed phosphates and polyphosphates in the coatings. The pigments contain cation in the most cases as aluminium…
Abstract
The paper deals with studying the anticorrosive properties of condensed phosphates and polyphosphates in the coatings. The pigments contain cation in the most cases as aluminium in a combination with zinc, strontium, calcium or a combination with all the cations. The investigated anticorrosive pigments differ in water solubility, inhibition efficiencies of their aqueous extracts and also the efficiencies in the coatings protecting steel substrate to corrosion. Two types of condensed anticorrosive pigments (polyphosphates and polyphosphosilicates) were compared. The anticorrosion properties of polyphosphosilicates are inferior to those of polyphosphates. The high anticorrosion efficiency was found at a comparative pigment, represented by zinc phosphosilicate.
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