Red Organic Pigments Research Articles

Microanalytical Characterization of an Innovative Modern Mural Painting Technique by SEM-EDS, NMR and Micro-ATR-FTIR among Others.

During the 20th century, modern painters experimented with different mediums and painting techniques, one of them was Rafael Coronel in his mural painting, Paisaje Abstracto (Abstract landscape). The painting was created with a peculiar pouring technique and an unknown binding medium; ageing produced fractures and severe conservation problems. Therefore, the characterization of the painting medium became an urgent matter in order to understand the current condition of the painting and to develop a proper treatment. The aim of this research was to characterize the chemical composition and painting technique of Paisaje Abstracto. To approach this goal two microsamples were taken and analyzed by optical microscopy (OM), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), nuclear magnetic resonance (NMR) spectroscopy, attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), micro attenuated total reflection Fourier transform infrared spectroscopy (micro-ATR-FTIR) and gas chromatography/mass spectrometry (GC/MS). The analysis allowed for the identification of cadmium sulfide (CdS) and titanium dioxide (TiO2) as inorganic pigments; aluminosilicate fillers; poly(methyl methacrylate) (pMMA) as a binder; MMA monomer, red organic pigment PR181; benzoyl peroxide, dibutyl phthalate and 1-octadecanol as organic additives. This study presents an innovative painting technique with pMMA, a medium not commonly used by artists, which was probably polymerized onto the painting support.

Kinetic characteristics of evaporative crystallization desalination of acidic high-salt wastewater

CLT acid (2-amino-4-methyl-5-chlorobenzenesulfonic acid) is a red organic pigment intermediate, which is widely used in textile printing and dyeing industry, but a large amount of acidic MgSO4 high-salt wastewater will be generated during the production process. Direct discharge not only wastes sulfates in wastewater, but also damages the environment. In this paper, a new treatment process is developed to separate and recover MgSO4 from high-salt wastewater by thermal evaporation crystallization method, which realizes the resource utilization and ensures the treatment effect. Through the evaporative crystallization kinetic experiment and the pilot experiment of acidic MgSO4 high-salt wastewater, the influence of operating conditions on the product crystal size and crystal size distribution was investigated. The results show that the crystal growth is completed when the residence time is 40 min, the stirring speed is 200 r/min, and the seed content is 3 g/L. In industrial production, crystallization and recrystallization should be carried out after removing organic matters. When the concentration ratio is 1.6, the purity of MgSO4 crystal reach 96 %, and the resources can be maximized.

Time-resolved fluorescence and anisotropy studies of red pigments present in acrylic formulations

Red organic pigments are frequently found in modern paintings and murals based on acrylic formulations. The detection of these molecules is valuable to guide investigations about cultural heritage and for restoration efforts. These studies usually employ microscopic amounts of materials that are obtained through swabbing or micro-sampling. In this contribution we describe the time-resolved emission properties of a set of red pigments with the objective of characterizing their excited state properties and developing strategies to identify their presence through fluorescence lifetime measurements, even in concentrations of the order of 10−9 M. As we show, using different solvent systems, the emission decay measurements can be setup to be a robust identification technique that avoids problems with evaporation or partial solubility. We also show that the sensitivity of these determinations is improved using a confocal type of setup with a high numerical aperture lens to ensure a high photon capture. This setup also allows for the samples to be prepared in microliter level volumes which implies a relatively high concentration of the pigments. In addition, we show that the lifetime measurements can be complemented with determinations of the emission anisotropy decays with the same experimental setup, which provides an additional property specific to each pigment, permitting an accurate differentiation between fluorophores.

Controlling the risks of nano-enabled products through the life cycle: The case of nano copper oxide paint for wood protection and nano-pigments used in the automotive industry

The widespread use of engineered nanomaterials (ENMs) in consumer products and the overwhelming uncertainties in their ecological and human health risks have raised concerns regarding their safety among industries and regulators. There has been an ongoing debate over the past few decades on ways to overcome the challenges in assessing and mitigating nano-related risks, which has reached a phase of general consensus that nanotechnology innovation should be accompanied by the application of the precautionary principle and best practice risk management, even if the risk assessment uncertainties are large. We propose a quantitative methodology for selecting the optimal risk control strategy based on information about human health and ecological risks, efficacy of risk mitigation measures, cost and other contextual factors. The risk control (RC) methodology was developed in the European FP7 research project SUN and successfully demonstrated in two case studies involving real industrial nano-enabled products (NEPs): nano-scale copper oxide (CuO) and basic copper carbonate (Cu2(OH)2CO3) used as antimicrobial and antifungal coatings and impregnations for the preservation of treated wood, and two nanoscale pigments used for colouring plastic automotive parts (i.e. red organic pigment and carbon black). The application of RC for human health risks showed that although nano-related risks could easily be controlled in automotive plastics case study with modifications in production technology or specific type of engineering controls, nano-related risks due to sanding and sawing copper oxide painted wood were non-acceptable in the use lifecycle stage and would need the identification of a more effective risk control strategy.

Spectroscopic Differentiation and Microscopic Imaging of Red Organic Pigments Using Optical Pump-Probe Contrast.

Analysis of red organic pigments in artworks (and in forensics applications) is challenging, because conventional nondestructive mapping techniques provide little contrast, and most chemical analyses with high specificity require sample removal. Here we demonstrate a new optical approach, pump-probe microscopy, for the analysis of red organic pigments. We investigate Carmine naccarat, Lac dye, purpurin, alizarin, madder lake, and eosin Y and show that their intrinsic photophysical properties produce distinctive pump-probe spectra. We utilize this contrast for high-resolution, three-dimensional imaging without the need for physical sample removal. Lastly, we highlight the potential of pump-probe microscopy as an analytical tool for forensics of other types of organic colorants by investigating a series of automotive paints.

Mathematical modeling of pigment dispersion taking into account the full agglomerate particle size distribution

The purpose of this work is to develop a mathematical model that can quantify the dispersion of pigments, with a focus on the mechanical breakage of pigment agglomerates. The underlying physical mechanism was assumed to be surface erosion of spherical pigment agglomerates. The full agglomerate particle size distribution was simulated. Data from two previous experimental investigations were used for model validation. The first concerns two different yellow organic pigments dispersed in nitrocellulose/ethanol vehicles in a ball mill and the second a red organic pigment dispersed in a solvent-based acrylic vehicle in a three-roll mill. When the linear rate of agglomerate surface erosion was taken to be proportional to the external agglomerate surface area, simulations of the volume-moment mean diameter over time were in good quantitative agreement with experimental data for all three pigments. The only adjustable parameter used was an apparent rate constant for the linear agglomerate erosion rate. Model simulations, at selected values of time, for the full agglomerate particle size distribution were in good qualitative agreement with the measured values. A quantitative match of the experimental particle size distributions could be obtained using time-dependent fragment distributions, but this resulted in a very slight improvement in the simulated transient mean diameter only. The model provides a mechanistic understanding of the agglomerate breakage process that can be used, e.g., in the development of novel dispersion principles and for analysis of dispersion failures. The general applicability of the model, beyond the three pigments considered, needs to be confirmed.

Surface protection of an organic pigment based on a modification using a mixed-micelle system

The surface of a model red organic pigment, 3,6-bis(4-chlorophenyl)pyrrolo[3,4-c]pyrrole-1,4-dione, was modified using a mixed-micelle system containing different surfactants and polymers to improve the dispersibility of the pigment. It is shown that modifying the surface using a non-ionic surfactant and a mixed-micelle solution leads to good dispersibility of the pigment. The surface-modified pigment particles were additionally encapsulated with a SiO2 shell to improve the UV/TiO2 fastness. The influence of the synthesis parameters, such as the temperature and the pH, on the formation of the SiO2 protective layer around the pigment particles and, consequently, on the UV/TiO2 protection were investigated. The conditions leading to a compact and uniform protective silica layer over the majority of the pigment particles are discussed in detail.

Non-invasive identification of traditional red lake pigments in fourteenth to sixteenth centuries paintings through the use of hyperspectral imaging technique

The present paper, which focuses on the identification of red lake pigments, in particular madder, brazilwood, and cochineal, addresses the advantages and drawbacks of using reflectance hyperspectral imaging in the visible and near-infrared ranges as a non-invasive method of discrimination between different red organic pigments in cultural heritage objects. Based on reconstructions of paints used in the period extending from the fourteenth to the sixteenth century, prepared with as far as possible historical accuracy, the analyses by means of visible/near-infrared reflectance hyperspectral imaging were carried out with the objective of understanding the most significant differences between these vegetal- and animal-based red lake pigments. The paper discusses the results that were obtained on four original Italian and North European paintings and compared with those from the paint reconstructions, in order to demonstrate how the hyperspectral imaging technique can be usefully and effectively applied to the identification and mapping of red lake pigments in painted surfaces of interest in the conservation field.

Raman analysis assessed by Fourier‐Transformed infrared and X‐ray fluorescence spectroscopies: a multi‐analytical approach of ancient chromolithographs from the 19th century

A set of chromolithographs from the 19th century were analysed to identify the fillers and pigments used for their elaboration. Because of the delicacy of the chromolithographs, the research involved the use of Raman, Fourier‐transform infrared and energy dispersive X‐ray fluorescence spectroscopies for a complete characterization of the works on paper without removing any microsamples. Despite the high fluorescence of the samples when analyzed by Raman spectroscopy, in this paper, we demonstrated that ink spectra can be successfully enhanced by subtracting the spectra of the supporting background paper. The results of the study showed that, apparently, the lithographer used a limited range of common inorganic pigments from the 19th century (carbon black, chrome yellow, Prussian blue, red ochre, red lead and vermilion) together with organic pigments (indigo blue, gamboge and a red organic pigment). The study also found that despite the fact that during the 19th and early 20th century the use of mixtures of several pigments was a common practice, unusual admixtures were used for the preparation of some colours of the studied chromolithographs. Copyright © 2011 John Wiley & Sons, Ltd.

Micellar electrokinetic chromatography method for the determination of several natural red dyestuff and lake pigments used in art work

The identification of organic colorants used in artistic paintings is an important information source for reconstructing the working techniques found in a particular work and for defining a programme for the restoration and conservation of the painting. In this work, sodium dodecyl sulfate (SDS) was used as a surfactant in micellar electrokinetic chromatography (MEKC) for separating a broad range of red organic pigments, based on their colouring matters: madder (colouring matters: alizarin, quinizarin and purpurin), cochineal (colouring matter: carminic acid), red sandalwood (colouring matter: santalin), brazilwood (colouring matter: brazilin), lac dye (colouring matter: laccaic acid) and dragon's blood (colouring matter: dracorhodin). The running electrolyte used was 20 mM borax (pH 9), containing 20 mM SDS and 10% acetonitrile as organic modifier. Separation was carried out by applying a +20 kV voltage at the injection end, 25 °C and 214 nm/254 nm as detection wavelengths. All colorants were separated within less than 13 min with a good baseline resolution. The method was applied to the analysis of paint samples obtained from the Diocesan Museum of Holy Art of Bilbao.

Effect of coloured pigmentation on titanium dioxide photo catalysed PVC degradation

Most organic coatings, regardless of colour, are pigmented with titanium dioxide (TiO2) to increase their covering power. TiO2 in its anatase crystal form is highly photoactive under ultraviolet (UV) irradiation. Photo activation of TiO2 causes the formation of free radicals, which can interact with the organic matrix, causing accelerated degradation of the polymeric coating. This releases carbon dioxide (CO2) via a series of reactions initiated by surface bound hydroxyl radicals. To identify which type and concentration of coloured pigment provides the most photostable formulation of TiO2 containing organic coating, model coatings containing different coloured pigments and loadings have been assessed using a novel flat panel irradiation reactor. The rate of CO2 evolved by the irradiated sample, measured using a Fourier transform infrared (FTIR) spectrometer, has been used to quantify the degradation induced by individual pigment combinations. Yellow chromium titanate pigments are ineffective in stabilisation of the TiO2 driven oxidation largely owing to poor light absorption properties and carbon black pigments are only effective at higher loadings where light absorption outweighs charge percolation. Red organic pigments can potentially sensitise degradation while the blue and green pigments tested offer the best stabilisation of TiO2 driven degradation over the range 0·1–10% per hundred resin (PHR) owing to their superior absorption of near ultraviolet A (UVA) light (at 380 nm) which activates the TiO2.

Improvements in the wallpaper industry during the second half of the 19th century: Micro-Raman spectroscopy analysis of pigmented wallpapers

Scientific studies of the pigments used in the manufacturing process of some pigmented wallpapers are presented in this work. Non-destructive micro-Raman spectroscopy was selected for this purpose, and provides important information about how the 19th century wallpaper industry incorporated new materials in their works and designs. At the same time, analysis can help to date the samples of uncatalogued wallpapers. Chrome yellow, burnt Sienna, Prussian blue, ultramarine blue, red lead, carbon black, calcium carbonate, red iron oxide and a red organic pigment were identified. According to the palette used, as well as to the manufacturing process, the wallpapers in this study can be dated to the second half of the 19th century.

Photopolymerization of pigmented thiol–ene systems

Photopolymerization kinetics and optical properties of pigmented thiol–ene coatings were investigated using photo-DSC, real-time FTIR, colorimetry, and AFM. Pigment has no deleterious effect on the unique ability of thiol–ene systems to photopolymerize in air. When trimethylolpropane tris-(3-mercaptopropionate) is incrementally added to tripropylene glycol diacrylate with and without calcium lithol rubine, a red organic pigment, the photopolymerization rate in nitrogen steadily decreases due to a shift in the polymerization mechanism from an acrylate homopolymerization to a thiol–ene copolymerization. However, the photopolymerization rate of pigmented and non-pigmented systems in air significantly increases with increasing thiol concentration, ultimately reaching a maximum at approximately 35 mole percent trifunctional thiol. The increase in rate is due to chain transfer from the non-reactive peroxy radical to the thiol. Thiol groups reduce oxygen inhibition to a greater degree than standard additives such as N-methyldiethanolamine, N-vinyl pyrrolidinone, and thioether containing trifunctional vinyl esters. For a typical acrylate based pigmented photocurable system, greater than 10 wt% photoinitiator is required to achieve a photopolymerization rate equivalent to a comparable thiol–ene system with 1 wt% photoinitiator in air. AFM and colorimetric data indicate that addition of trifunctional thiol has no deleterious effect on pigment dispersion and may in fact increase dispersion quality.

Design of polymeric dispersants for waterborne coatings

Block and random copolymers of ammonium methacrylate and dimeth-ylaminoethyl methacrylate have been synthesized and tested as dispersants of various organic and inorganic pigments in formulations for waterborne paints. Blockiness of the co-monomer distribution is a prerequisite for good color characteristics in the final paint. It is however noteworthy that a tapered diblock (one-step anionic synthesis), a diblock copolymer with a regular change in composition from one block to the other one, has an interfacial activity quite comparable to the parent “pure” diblock copolymer (two-step anionic synthesis). The most interesting observation is that the poly(dimethylaminoethyl methacrylate) anchoring block can impart stability to dispersions of pigments as different as iron oxide, a blue Cu-phthalocyanine pigment, and a red organic pigment based on pyrrole in representative aqueous paint formulations. This type of diblock copolymer is promising for the design of universal dispersants.

Pigmentation evaluation of talc in polypropylene

AbstractNew automotive and appliance applications require increased use of color matched pigmentation. End uses for the colored compounds include automotive interior and exterior applications, home appliances, tools, and lawn and garden equipment. The effects of “Platyness,” “Fineness,” and “Whiteness” are studied to better understand the contribution of each variable to compound color development in the presence of a red organic pigment.

The materials of J.M.W. Turner: pigments

Analyses of pigments from palettes used by J.M.W. Turner (active c.1792–c.1850) by means of microscopy, microchemical analysis, thin-layer chromatography, energy-dispersive X-ray analysis, X-ray diffraction and Fourier transform infrared spectroscopy are given. The occurrence of pigments in Turner's dated oil paintings and watercolours is also given, arranged by five-year periods. These findings are discussed in the context of published analyses of pigments from the first half of the nineteenth century. Turner used cobalt blue, emerald green, viridian, orange vermilion, barium chromate, chrome yellow, chrome orange and chrome scarlet within a few years of their known dates of discovery. It has become clear that Turner was using, or at least experimenting with, practically all the pigments known to be available at that time. In a few cases, in the light of these results, ideas on the availability of pigments to English artists have been revised backwards to the first known date of manufacture. Turner also possessed and used a wide range of red and yellow organic pigments, but few organic greens. The dyestuff extracted from Rubia tinctorum L. madder on an aluminiumcontaining substrate can be distinguished from the same madder on different substrates by its strong pink fluorescence in both ultraviolet and green light. The other red organic pigments (a second madder, brasilwood and cochineal dyestuffs on a range of substrates containing aluminium, copper, iron, aluminium/copper and clays) show negligible fluorescence. The red organic pigments were used in oil medium as well as watercolour, the yellows only in watercolour medium.

Red Pigments in Petroleum Exploration

Naturally occurring plant and animal pigments have long aroused intense scientific interest. The vivid red organic pigments, the petroporphyrins, present as minor components of many sediments and petroleums, are now receiving increasing attention in the field of organic geochemistry. First observed 50 years ago, and thought to arise in part from the green photosynthetic pigment chlorophyll in ancient organisms, they provided the first firm evidence for a biogenic origin for petroleum. Recent improvements in microanalytical chemical techniques have shown that the petro porphyrins are generally complex mixtures of a variety of closely related structural types. The distributions of the components as revealed by direct insertion probe mass spectrometry (MS), high-performance liquid chromatography (HPLC) and computerised gas chromatography-mass spectrometry (CGCMS) can provide a record of the original depositional palaeoenvironment and subsequent thermal history of the sedimentary matrix. The petroporphyrins are finding increasing application as a maturity parameter in petroleum geochemistry, complementing information from other biological marker components, and, in conjunction with geological and geophysical measurements, they can help to enhance the efficiency of exploration programmes.

Preparation of Red Organic Pigment with Phenylated Silica Gel as Core

Abstract The silanols on the surface of silica gel were chlorinated and a phenyl group was introduced onto the silica gel (Remark: Graphics omitted.) by phenylating with phenyllithium. The surface group was derived to a structure similar to Sudan I by nitration, reduction, diazotization, and coupling (with 2-naphthol). The prepared pigment showed approximately the same color as Sudan I, and had very good resistance to water.

Influence of pigments on the light stability of polymers: A critical review

Pigments can have significant influences, both favourable and unfavourable, on the light stability of polymer formulations. This paper reviews information on the manifestations of pigment influences on polymer stability and on their underlying causes. It aims to provide some understanding of the complex phenomena, identify possible causes of unfavourable pigment effects on polymer light stability, and provide some direction for improving the light stability of polymer-pigment-stabiliser systems of unfavourable performance. Favourable pigment influences on polymer light stability may be due to screening of harmful radiation, selective absorption of harmful radiation, and deactivation of polymer photoexcited species. Negative influences may be due to initiation of polymer photo-oxidation by photoexcited pigment chromophores, adsorption or chemical transformation of stabilising additives, influence on polymer morphology, or sensitisation of singlet oxygen formation. Pigment-polymer-stabiliser interactions are complex. Much work is needed to understand them better. A special challenge is a better understanding of why some orange, yellow, and red organic pigments exhibit negative influences on pigment light stability.

有機系赤色顔料に関する研究 (第7報)

有機系赤色顔料に関する研究 (第7報)