Pigment Particles Research Articles

Peculiarities of the magneto-optical response in dispersions of anisometric pigment nano-particles

We demonstrate an unusually strong magneto-optical response of elongated plate-shaped pigment particles in magnetic fields ranging from 0 to 25 T.

Characteristics and aerosol size distributions of metal-containing paint particles at a spray-painting workplace

The health effects of metal-containing paint-particles at various particle-size distributions on workers in a spray-painting workplace at an industrial ventilation equipment manufacturing plant.

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.

Dynamic and Permanent Gratings in Suspensions of Absorbing Nanocrystals in Organic Solvent

Both dynamic and permanent optical gratings were recorded in the suspension of absorbing pigment nanocrystallites in organic solvent. The dynamic gratings were recorded due to the transfer of the nanocrystallites in the temperature gradient induced by light interference pattern, and the permanent gratings were formed due to light-induced adsorption of the nanocrystalites on the surface of the cell substrate. Full Text: PDF References B.Y. Zel'dovich, N. V Tabiryan, "Orientational optical nonlinearity of liquid crystals", Sov. Phys. Uspekhi 28, 1059 (1985). CrossRef K. Thyagarajan, P. Lallemand, "Determination of the thermal diffusion ratio in a binary mixture by forced Rayleigh scattering", Opt. Commun. 26, 54 (1978). CrossRef F. Bloisi, L. Vicari, P. Cavaliere, S. Martellucci, J. Quartieri, P. Mormile, G. Pierattini, A. Felice, "Soret effect in forced Rayleigh scattering", Appl. Phys. B 106, 103 (1987). CrossRef W. Köhler, "Thermodiffusion in polymer solutions as observed by forced Rayleigh scattering", Chem. Phys. 98, 660 (1993). CrossRef J. Zamir Anvari, R. Karimzadeh, N. Mansour, "Thermo-optic properties and nonlinear responses of copper nanoparticles in polysiloxane oil", J. Opt. 12, 035212 (2010). CrossRef N.M. Rouhollah Karimzadeh, "Investigation of the Soret effect in copper nanoparticle colloids by self-phase modulation and Z-scan", J. Mod. Opt. 60, 163 (2013). CrossRef N. Tabiryan, W. Luo, "Soret feedback in thermal diffusion of suspensions", Phys. Rev. E 57, 4431 (1998). CrossRef A. Eremin, R. Stannarius, S. Klein, J. Heuer, R.M. Richardson, "Switching of Electrically Responsive, Light-Sensitive Colloidal Suspensions of Anisotropic Pigment Particles", Adv. Funct. Mater. 21, 556 (2011). CrossRef I.C. Khoo, "Nonlinear optics of liquid crystalline materials", Phys. Rep. 471, 221 (2009). CrossRef H. Löwen, "Anisotropic self-diffusion in colloidal nematic phases", Phys. Rev. E 59, 1989 (1999). CrossRef S. Kredentser, A. Eremin, P. Davidson, V. Reshetnyak, R. Stannarius,Y. Reznikov, submitted to Eur. Phys. J. E (2015). CrossRef

Particle Size, Morphology and Color Characteristics of C.I. Pigment Red 57:1 : 2. Effect of Salt Milling Process

The effect of salt milling process on the crystal size, morphology, and color characteristics of C.I. Pigment Red 57:1 was studied. The primitive morphology and color properties of the pigment after synthesis were studied in the former series work. The size and morphology of primary particles and the second aggregation features should be considered because they are very important to determine pigment quality. We compared the primary morphology of pigment particles before drying with the secondary aggregated morphology of pigment particles after drying and salt milling process. Morphological properties were investigated by particle size analysis, X-ray diffraction, and scanning electron microscopy and color measurement was carried out. Significant reduction in particle size as well as enhanced crystallite size after salt milling process was observed. This result might give a difference in color of the pigment, turning into brighter and more blue-toned red color. It was revealed that synthesis condition affect the morphology and color of the pigment even after milling. Increase in HCl concentration in the synthesis process enhanced crystal size and quality forming bluer-red pigments but an increase in concentration resulted in more amorphous crystals forming darker-red pigments after salt milling.

Far-reaching geometrical artefacts due to thermal decomposition of polymeric coatings around focused ion beam milled pigment particles.

Focused ion beam and scanning electron microscope (FIB-SEM) instruments are extensively used to characterize nanoscale composition of composite materials, however, their application to analysis of organic corrosion barrier coatings has been limited. The primary concern that arises with use of FIB to mill organic materials is the possibility of severe thermal damage that occurs in close proximity to the ion beam impact. Recent research has shown that such localized artefacts can be mitigated for a number of polymers through cryogenic cooling of the sample as well as low current milling and intelligent ion beam control. Here we report unexpected nonlocalized artefacts that occur during FIB milling of composite organic coatings with pigment particles. Specifically, we show that FIB milling of pigmented polysiloxane coating can lead to formation of multiple microscopic voids within the substrate as far as 5 μm away from the ion beam impact. We use further experimentation and modelling to show that void formation occurs via ion beam heating of the pigment particles that leads to decomposition and vaporization of the surrounding polysiloxane. We also identify FIB milling conditions that mitigate this issue.

Utilizing cellulase as dispersant to prepare stable nano-pigment suspension and investigating its coloring performance on cotton fabrics

In this research, a novel nano-pigment suspension was successfully prepared in an ultrasonic disruptor using crude cellulase as dispersant. The colloidal and rheological properties of this cellulase-based suspension such as zeta potentials, particle distribution and apparent viscosity were analyzed. The measurement of zeta potentials showed that the surface charges of pigment were adjustable along with the acid–base properties of external environment due to the amphoteric character of cellulase proteins. Subsequently, its stability to high-speed centrifuge, freeze–thaw treatment and ion intensity was carefully investigated. Thermo-gravimetric analysis (TGA) was conducted to demonstrate the coverage of pigment particles by cellulase proteins. Furthermore, X-ray diffraction (XRD) characterization was utilized to disclose the combined impacts of cellulase and ultrasonic power on the crystal structures of pigment. At last, the coloring performance of this charge-adjustable nano-pigment suspension on cotton substrates was evaluated by measuring their K/S values and color fastness. Scanning Electron Microscope (SEM) was carried out to give a direct observation of the nano-pigment distributed on cotton surfaces.

Diffusion process of an ink drop in core–shell silica–titania pigment particles

Recording coatings have been successfully prepared by the core–shell structural silica–titanium dioxide particles, which were synthesized using sol–gel methods and fabricated as a close-packed colloidal crystalline array. The size of the nano-silica particles (50–100nm) was controlled via varying the concentration of ammonium hydroxide. The silica spheres coated with titania (core–shell structure) were prepared by a self-assembly coating deposition process. Transmission electron microscopy and scanning electron microscopy were used to analyze the microstructure of the core/shell composite particles. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy were used to analyze the molecular structure of the composite particles and the formation of the chemical bonds (Ti–O and Ti–O–Si) on the shell surface. The prepared composite pigment particles were applied in recording materials. The diffusion process of the ink drop on the surface of the recording materials was studied by the edge detection method. We also investigated the role of the ink drop in the diffusion process of the different composite pigment particle.

Aluminium X-ray absorption near-edge spectroscopy analysis of discoloured ultramarine blue in 20th century oil paintings

A specific case of synthetic ultramarine degradation was observed in three oil paintings from the early 20th century. Pigment particles were found to have been discoloured, resulting in intricate patterns of white lines, approximately 10 to 30 microns wide, criss-crossing the paint surface. Colour in ultramarine pigments comes from the encapsulated sulphur radical anions, chromophores, inside the cage framework built from SiO44− and AlO45− tetrahedral units linked by the oxygen atoms. In healthy pigment, the charge is balanced by cations such as sodium and the framework stabilises the reactive radicals, preserving the colour. This discolouration mechanism was investigated using X-ray near edge spectroscopy (XANES).XANES was used at the aluminium K-edge to investigate the coordination of the Al atoms in the pigment framework. Using the focused synchrotron beam available at the PHOENIX beamline from the Swiss Light Source, scans with high spatial resolution (5μm) and with a relatively low (2μm) depth interaction could be performed, enabling analysis of the discoloured lines on samples collected from one of the paintings. The comparison of spectra from healthy (blue) and discoloured (white) areas, supported a degradation mechanism involving the removal of aluminium atoms from tetrahedral coordination in the ultramarine framework, which results in the formation of six-coordinate aluminium compounds separate from the pigment structure. This causes a permanent opening of the cage framework, enabling the reaction of the chromophore and subsequent colour loss.

Micro FTIR imaging for the investigation of deteriorated organic binders in wall painting stratigraphies of different techniques and periods

This work deals with the detection and imaging of metal oxalates/carboxylates in the paint layers of ancient wall paintings and with the investigation of their possible association with the ageing of organic substances used as binding media in the original painting. This assumption is investigated employing Fourier transform infrared (FTIR) imaging on several case studies; starting with a thin section of the paint stratigraphy extracted from extensively deteriorated post-Byzantine murals, painted with an oil binder. Metal carboxylates and oxalates show their maximum concentration at the interface of free fatty acids and pigment particles, indicating a possible origin of their formation. Then, the methodology was applied in paint thin sections, originating from Prehistoric, Roman and Hellenistic wall paintings. In these case studies, metal oxalates detected within the paint layers were explored regarding their relation to the use of an organic binder in the wall paintings. The chemical images of calcium oxalates in the paint layers of the Prehistoric wall paintings was a trigger for further laborious investigation on numerous samples, which resulted in revealing the spectrum of an aged proteinaceous binding medium. Thereafter, the distribution of metal oxalates within the paint layers of the samples from the Roman and Hellenistic wall paintings, unaffected by any later intervention, was assumed as an indirect indication of the use of an original organic binder.

Role of Acrylic Copolymers in Designing Environmentally Friendly Technologies for Finishing Textile Materials

We present the results of studies aimed at designing environmentally friendly technologies for printing and final finishing of textile materials. The technologies are based on the specific properties of carboxylated acrylic copolymers that can increase the viscosity in an alkaline medium. The obvious connection between negative changes in nature and the anthropogenic impact of industrial plants on the environment has raised general concerns, and requires solving a number of problems involved in the indicated issue. The negative impact of industrial activity on natural processes and living organisms is due not only to its wasteful management but also to shortcomings in the production processes employed [1]. Within the broad range of sectors in the national economy, the textile industry makes an appreciable contribution to environmental pollution and pollution of water and air basins. Considering this fact, improving processes in dyeing-and-finishing departments and designing environmentally friendly technologies for finishing textile materials is a timely and important direction in solving the important problem of reducing the level of toxicological and ecological stress on the environment and designing environmentally friendly textiles meeting international safety and quality standards. In this paper, we present the results of studies to develop environmentally friendly printing and final finishing using acrylic latexes and water-soluble copolymers of domestic manufacture (Nord Sintez LLC). In this case, improvement of the environmental situation is achieved as a result of the following: – using few-component pigment compositions, not containing toxic crosslinking agents; – improving the degree of utilization of reactive dyes and reducing their desorption during washing of printed material, with a corresponding decrease in their input into wastewaters from the dye-and-finishing plant; – designing low-formaldehyde and formaldehyde-free coupling agents, ensuring permanence and high resistance of the effects of final finishing to organic solvents. In the first step, we evaluated the properties of aqueous dispersions of acrylic and styrene-acrylic latexes of domestic manufacture, with the objective of using them as binders in the composition of pigment printing inks. The acrylic latex recommended for use is a copolymer of butyl acrylate, methyl methacrylate, acrylonitrile, and acrylic acids with the optimal ratio of “hard” and “soft” monomer units in the macromolecular chain, which ensures the needed combination of strength and elasticity of the polymer film. Such films are distinguished by high weathering resistance and form coatings that do not yellow over time, in contrast to films based on diene structures which tend to oxidize [2]. We established that an aqueous dispersion of acrylic carboxyl-containing latex MN-10 has low surface tension (36.7 mN/m), comparable with its value for divinyl nitrile latexes BNK 40/4 and BNK 20/35 (respectively 38.4 and 33.1 mN/m). The effective wettability and penetration of cellulose-containing fabrics by printing compositions based on this latex promotes stronger fixation of the pigment particles to the fiber substrate. The light scattering method has shown (Fig. 1) that the average size of MN-10 latex globules is not more than 100 nm, which is responsible for the high degree of homogeneity of the films and their stronger fixation to the polymer substrate [3].

Potential Threat of Microplastics to Zooplanktivores in the Surface Waters of the Southern Sea of Korea.

The potential impact of microplastic to zooplanktivores was assessed by measuring a ratio of neustonic microplastics to zooplankton by abundance in the southern sea of Korea. Neustonic microplastics and zooplankton (0.33-2 mm) were collected using a 330-μm mesh Manta trawl in Geoje eastern Bay and Jinhae Bay before and after the rainy season in 2012 and 2013. The mean microplastic to zooplankton ratios were 0.086 (May) and 0.022 (July) in 2012, and 0.016 (June) and 0.004 (July) in 2013, indicating that zooplanktivores could be more likely to feed on microplastics than natural preys before the rainy season in 2012 and 2013. In particular, the relatively high ratio occurred in a semi-enclosed bay characterized by a shipyard and a beach resort in Geoje Bay, and at stations close to a wastewater treatment plant and an aquaculture facility in Jinhae Bay before the rainy season. Among dominant microplastics and zooplankton before the rainy season, meroplankton of macrobenthos could be confused with paint particles in Geoje Bay, 2012, whereas Styrofoam could be mistaken as immature copepods by predators in Jinhae Bay, 2013. These observations suggest that zooplanktivores could be more likely to feed on microplastics than natural preys around Geoje and Jinhae Bays before the rainy season.

Influence of Animal Glues Application for Painting Restoration on Paper Characteristics

Artists have been used animal glues for a long time as binding and sizing materials of paintings in many countries including Korea. Since animal glues as a binding material lose their own adhesive strength by aging, pigment particles or pigment layers are easily detached from painting surface. Restaurators prefer to use animal glues for consolidation of pigment particles or pigment layers because artists use animal glues as a binder for their painting works. It is widely known that animal glues have different characteristics such as viscosity, stability on water etc. But there are still a few requirements to consider their stabilities for the restoration of paintings. Therefore, this study was aimed to evaluate of stability and efficiency of animal glue applications. The efficiency of animal glue application was decreased with increasing the concentration of animal glue solution. This result means the simple tendency, but does not representative data for other animal glues made from same raw materials. In most cases, the surface and mechanical characteristics of animal glues are dependent on some factors, like viscosity and concentration of animal glue solution.

Numerical study of particle deposition in electrostatic painting near a protrusion or indentation on a planar surface

The edge effect and the Faraday cage effect are two major problems that occur when the target surface contains sharp corners and recessed areas. This can significantly affect the electric field and degrade the deposition uniformity of paint, which is important in electrostatic painting. A numerical study is presented in this paper to investigate the methods to minimize these problems. A 2D axisymmetric numerical model is proposed to analyze the electric field distribution in the electrostatic painting system, assuming a grounded target with a small surface perturbation at the center using COMSOL. Simulations have been performed for different configurations on the target, different values of the corner radius and the space charge. Also, simulations of paint particle trajectories and deposition have been obtained using ANSYS to examine the effect of the particle size and the charge-to-mass ratio on the coating buildup rate of a flat target and a target with an indentation or a protrusion. The injections of mono- and poly-dispersed uncharged and charged particles were considered. The results suggest that preliminary analysis of the electric field distribution on a target having a perturbation provides a simple design tool for predicting coating uniformity.

White zinc in linseed oil paintings: chemical, mechanical and aesthetic aspects

The interest of this research derived from the request for a scientific investigation of the observed phenomenon from by few contemporary artists who, in some occasions, observed the formation of crequalure in rethinking areas where a paint layer of different colour was over imposed to a zinc white layer, on commercial canvases. To investigate this phenomenon several investigations to characterized chemical and physical proprieties of commercial white zinc pigments are carried out: XRD, ICP/OES, SEM/EDS, FTIR, GC-MS. Moreover, to several tests were performed in order to evidence the different behavior of the various white pigments referring to the miscibility and to the drying times. The paper shows how the size of the pigment particles affects the formation and the type of the craquelure.

Abundance and Distribution Characteristics of Microplastics in Surface Seawaters of the Incheon/Kyeonggi Coastal Region.

Microplastics in marine environments are of emerging concern due to their widespread distribution, their ingestion by various marine organisms, and their roles as a source and transfer vector of toxic chemicals. However, our understanding of their abundance and distribution characteristics in surface seawater (SSW) remains limited. We investigated microplastics in the surface microlayer (SML) and the SSW at 12 stations near-shore and offshore of the Korean west coast, Incheon/Kyeonggi region. Variation between stations, sampling media, and sampling methods were compared based on abundances, size distribution, and composition profiles of microsized synthetic polymer particles. The abundance of microplastics was greater in the SML (152,688 ± 92,384 particles/m(3)) than in SSW and showed a significant difference based on the sampling method for SSWs collected using a hand net (1602 ± 1274 particles/m(3)) and a zooplankton trawl net (0.19 ± 0.14 particles/m(3)). Ship paint particles (mostly alkyd resin polymer) accounted for the majority of microplastics detected in both SML and SSWs, and increased levels were observed around the voyage routes of large vessels. This indicates that polymers with marine-based origins become an important contributor to microplastics in coastal SSWs of this coastal region.

Materials, Techniques, and Conservation of Historic Stained Glass “Grisailles”

A grisaille is a brown‐blackish paint applied onto the inner surface of stained glass to draw the contours and details of the figures and to produce the effect of shades and volumes. Grisailles were traditionally made of finely ground oxides of iron but also of copper, zinc, lead, or manganese mixed with a flux such as lead ground glass and a binder and fixed onto the flat glass by firing. The grisailles have typical layer thickness varying between 10 and 100 μm and are formed by a complex mixture of pigment particles, crystalline, and amorphous reaction compounds, aging, and weathering compounds. The high brilliance, collimation, energy selection, and monochromacity of the SR beam are ideal to obtain micro‐XRD patterns from thin cross sections of the grisailles. The analyses are complemented with SEM‐EDX and LA‐ICPMS. A selection of grisailles from several cathedrals and buildings in Spain, Avila, Burgos, Alcalá de Henares, and in particular from Segovia, dating from early 16th to the 20th century and belonging to several master glaziers are studied. Changes in the methods of production and materials in the different historical periods are obtained and also related to the conservation state of the materials.

Ecological effects of Irgarol 1051 and Diuron on a coastal meiobenthic community: A laboratory microcosm experiment

After the Tributyltin world ban, Irgarol 1051 and Diuron have been the most commonly used biocides in antifouling paints. When adsorbed to suspended particulate matter or introduced as paint particles, these compounds accumulate in marine sediments and potentially cause ecological damage to benthic organisms. Therefore, a microcosm experiment was designed to evaluate the effects of Irgarol 1051 and Diuron, individually, on a meiofaunal community with emphasis on the dominant nematode assemblages. The experiment tested two factors: “Treatment” (two types of controls and three environmentally relevant concentrations of each contaminant) and “Exposure time” (5, 15 and 30 days). Significant declines in meiofauna density, nematode species richness and diversity, and changes in multivariate community structure were observed for both biocides at all exposure levels when compared to controls. Decreases occurred early on, within five days of exposure, which suggests that mortality, and not sub-lethal effects, has befallen upon the organisms. Sediment chlorophyll a and pheopigment concentrations, and redox potential were monitored to verify any indirect effects to the fauna through changes in the environment and results gave no indications of such mediated effects pointing to a direct toxic effect of both Irgarol and Diuron on the meiofauna. Although contaminated treatments showed a significant decline in the relative abundances of a particular functional group represented by the larger, longer-lived species, we did not observe the typical expected switch to smaller, more opportunistic taxa. Indeed, differences between controls and contaminated treatments were mainly due to an overall reduction in densities of the most abundant species in contaminated treatments. The high mortality (ca. 50% decline in total abundances), changes in community structure and species loss observed at biocide levels frequently encountered in the field suggest Irgarol and Diuron as a threat to benthic communities. Such severe effects contrast to other studies that have detected lower impacts, suggesting the free-living nematodes as potential indicators of marine pollution and the microcosm approach using natural communities as an impending tool for ecotoxicological studies.

Physico‐Chemical Characterization of Pigments and Binders of Murals in a Church in Ethiopia

Here, we report the physico‐chemical characterization of wall paintings from the Petros and Paulos church in Ethiopia. This work represents the first technical study of paintings located in Ethiopia, rather than paintings in museum collections outside the country, using diverse analytical techniques. In situ examination with a portable X‐ray fluorescence spectrometer (pXRF) was followed by analysis of samples using optical microscopy (OM), scanning electron microscopy coupled with energy‐dispersive X‐ray spectroscopy (SEM/EDS), micro‐Raman spectroscopy (MRS), attenuated total reflection – Fourier transform infrared spectroscopy (ATR‐FT–IR), X‐ray powder diffraction (XRD) and pyrolysis gas chromatography – mass spectrometry (Py‐GC/MS). The paint stratigraphy, the compositions of the support material, the preparatory and painting layers were studied, as well as the morphology of the pigment particles. The results revealed the use of earth pigments and carbon black. The preparatory layer was uncommon; composed of dolomite, clay rich in clinochlore and sand, in contrast to the more common gypsum and calcite. The binder and the stratigraphic analyses suggested a distempera technique.

Marine neustonic microplastics around the southeastern coast of Korea

We investigated floating debris around the mouth of the Nakdong River in the Southeastern Sea of Korea using a Manta trawl (330-μm mesh) and hand-net (50μm) before (May) and after (July) the rainy season in 2012. Microplastic (<2mm) was present at all of the stations, whereas Styrofoam (2–5mm) peaked only at a few stations far from the Nakdong River mouth in July. The dominant types were fibers (polyester), hard plastic (polyethylene), paint particles (alkyd), and Styrofoam (expanded polystyrene). The average abundances of fibers and hard plastic (<2mm) in the trawl were significantly higher in July than in May (p<0.005, p<0.05, respectively), while two orders of magnitude more microplastics (<2mm) were collected with the hand-net than with the trawl. Fibers and hard plastic by trawl were significantly compared temporally, and the hand-net proved the missed microplastics (50–330μm) when trawl used.