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Pigment Particles (pigment + particle)

Distribution by Scientific Domains

Polymers and Materials Science	66%

Selected Abstracts

A Facile Synthesis and Characterization of Monodisperse Spherical Pigment Particles with a Core/Shell Structure,

ADVANCED FUNCTIONAL MATERIALS, Issue 9 2007
C. Lin
Abstract In this paper, a facile sol,gel process for producing monodisperse, spherical, and nonaggregated pigment particles with a core/shell structure is reported. Spherical silica particles (245 and 385,nm in diameter) and Cr2O3, ,-Fe2O3, ZnCo2O4, CuFeCrO4, MgFe2O4, and CoAl2O4 pigments are selected as cores and shells, respectively. The obtained core/shell-structured pigment samples, denoted as SiO2@Cr2O3 (green), SiO2@,-Fe2O3 (red), SiO2@MgFe2O4 (brown), SiO2@ZnCo2O4 (dark green), SiO2@CoAl2O4 (blue), and SiO2@CuFeCrO4 (black), are well characterized by using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and UV-vis diffuse reflection, as well as by investigating the magnetic properties. The results of XRD and high-resolution TEM (HRTEM) demonstrate that the pigment shells crystallize well on the surface of SiO2 particles. The thickness of the pigment shell can be tuned by the number of coatings, to some extent. These pigment particles can be well dispersed in some solvents (such as glycol) to form relatively more stable suspensions than the commercial products. Apart from the color characteristics, some of pigments like SiO2@Cr2O3, SiO2@MgFe2O4, and SiO2@CuFeCrO4 also show magnetic properties with coercivities of 1098,Oe (5,K), 648,Oe (5,K), and 91,Oe (298,K), respectively. [source]

The Use of an Exact Light-Scattering Theory for Spheroidal TiO2 Pigment Particles

PARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Issue 2 2006
Juho-Pertti Jalava
Abstract Titanium dioxide pigments are widely used, e.g., in paints, printing inks, plastics, and papers, because of the excellent and whiteness they provide. As is well known, the opacity and to it related optical properties depend on the pigment's crystal- and particle-size distributions (CSD, PSD). Therefore, the process and quality control of the CSD and PSD are very essential. The development of a straightforward and sophisticated method for process and quality control is presented here. The principal component is a new determination method for the PSD based on an accurate theory of light scattering of spheroidal particles. In this new method, called the turbidity spectrum method (TSM), the whole turbidity spectrum is measured. This spectrum, which is due to the particle-size distribution of the pigment particles, is then solved using the T-matrix method by taking into account the shape of the particles. After that the CSD is extracted from the PSD. The T-matrix method is one of the most powerful and widely used tools for the rigorous computing of electromagnetic scattering by non-spherical particles. The repeatability of the mean PSD (,200,nm) obtained by the TSM is excellent, with a standard deviation of 0.1,nm (0.05,%). Linear regression models based on TSM results were developed for undertone and tint-reducing power, which are important optical parameters of the pigment. The excellent repeatability of the TSM results was necessary for the production of representative models. [source]

A Facile Synthesis and Characterization of Monodisperse Spherical Pigment Particles with a Core/Shell Structure,

High-pressure paint-gun injury of the finger simulating giant cell tumor of tendon sheath

JOURNAL OF CUTANEOUS PATHOLOGY, Issue 2 2005
Catherine M. Stefanato
At this pressure, paint will penetrate the skin and spread quickly through fascial planes and tendon sheaths. The present case is that of a lesion from the finger of a 35-year-old white male in whom a history was initially unavailable. Histologic examination revealed diffuse fibrohistiocytic proliferation and giant cells, with numerous darkly pigmented, uniformly small-sized particles throughout the lesion. The initial impression was that of a giant cell tumor of tendon sheath. However, the pigment particles were negative for Perls stain, and polariscopic examination revealed clear refractile fragments. These findings raised the possibility that the lesion was the result of a traumatic event. On further inquiry, it was revealed that the patient had sustained a high-pressure paint-gun injury 1 year earlier. The simulation, histopathologically, of a giant cell tumor of tendon sheath by a high-pressure paint-gun injury has not, to our knowledge, been reported previously, nor has the histologic finding of small, uniformly sized pigment particles and polarizable refractile fragments in this particular type of injury. [source]

The Use of an Exact Light-Scattering Theory for Spheroidal TiO2 Pigment Particles

Photocatalytic Coatings for Environmental Applications,

PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 2 2005
Norman S. Allen
ABSTRACT A series of nano- and micronparticle-grade anatase and rutile titanium dioxide pigments have been prepared with various densities of surface treatments, particle size and surface area. Their photocatalytic activities have been determined in a series of paint films by FTIR, chalking, color, gloss change and weight loss after artificial weathering. The pigments have also been examined by rapid assessment methodologies using photodielectric microwave spectroscopy, 2-propanol oxidation and hydroxyl analysis. The microwave response under light and dark cycles provides an extended timescale probe of chargecarrier dynamics in the pigments. Pigment particle size, surface area and properties clearly play an important role in dispersion and any polymer-pigment interactions. Photooxidation studies on several types of paint films show a clear demarcation between nanoparticle- and pigmentary-grade titanium dioxide, with the former being more active because of their greater degree of catalytic surface activity. The photosensitivity of titanium dioxide is considered to arise from localized sites on the crystal surface (i.e. acidic OH), and occupation of these sites by surface treatments inhibits photoreduction of the pigment by ultraviolet radiation; hence, the destructive oxidation of the binder is inhibited. Coatings containing 2,5% by weight alumina or alumina and silica are satisfactory for generalpurpose paints. If greater resistance to weathering is desired, the pigments are coated more heavily to about 7,10% weight. The coating can consist of a combination of several materials, e.g. alumina, silica, zirconia, aluminum phosphates of other metals. For example, the presence of hydrous alumina particles lowers van der Waals forces between pigments particles by several orders of magnitude, decreasing particle-particle attractions. Hydrous aluminum oxide phases appear to improve dispersibility more effectively than most of the other hydroxides and oxides. Coated nanoparticles are shown to exhibit effective light stabilization in various water- and oilbased paint media in comparison with conventional organic stabilizers. Hindered piperidine stabilizers are shown to provide no additional benefits in this regard, often exhibiting strong antagonism. The use of photocatalytic titania nanoparticles in the development of self-cleaning paints and microbiological surfaces is also demonstrated in this study. In the former case, surface erosion is shown to be controlled by varying the ratio of admixture of durable pigmentary-grade rutile (heavily coated) and a catalytic-grade anatase nanoparticle. For environmental applications in the development of coatings for destroying atmospheric pollutants such as nitrogen oxide gases (NOX), stable substrates are developed with photocatalytic nanoparticle-grade anatase. In this study, porosity of the coatings through calcium carbonate doping is shown to be crucial in the control of the effective destruction of atmospheric NOx gases. For the development of microbiological substrates for the destruction of harmful bacteria, effective nanoparticle anatase titania is shown to be important, with hydrated high surface area particles giving the greatest activity. [source]