Лако-красочные материалы — производство

The term texture generally is used to mean the feel — that is, the rough­ness or smoothness, and the softness or hardness experienced when a pigment is rubbed between the fingers. The more general meaning in the pigment and coating industry is the relative ease of dispersion of a pigment in a paint vehicle. The […]

Pigments vary not only in size but also in particle shape. Although the inherent shape of pigment particles is determined from its crystal Figure 3.4: Shapes of primary pigment particles form, it also depends to some extent on the method of synthesizing the pigment. In general, wet-ground pigments tend to have smoother and rounder edges […]

All particles in a given pigment are not identical in size; rather, they are a mixture of particles with different sizes. Therefore, pigments are generally evaluated for their mean particle size and particle size distribution by means of the following methods: • Sieve analysis • Accelerated sedimentation, such as centrifugal and ultra-centrifugal • Light attenuation […]

Particle size and particle size distribution are very important cha­racteristics of pigments because they influence various optical pro­perties of the paint such as color (Section 3.2.1.1), hiding power/ opacity (Section 3.2.1.2), tinting strength (Section 3.2.1.3) and gloss, as well as physical properties such as suspension of particles in the paint and rheology of the paint […]

The density of a pigment may be determined by the pycnometer method at a standard temperature of 25 °C using kerosene as immersion liquid. The detailed procedure may be found in ISO 787­10 and ASTM D153. Many pigments are tested disregarding air entrapment on the par­ticle surfaces or in the voids between the particles. The […]

Density can be a useful pointer to such properties of a pigment when dispersed in paint as suspension and density of the paint itself. According to Stokes’ law, a pigment particle will settle in paint at a rate proportional to the difference in the densities of the pigment and the medium. Therefore, paints with dense […]

Tolerance to an individual solvent is tested by enclosing a certain amount of pigment powder in a piece of filter paper, which is then immersed in the organic solvent for a given amount of time. The extent of coloration of the test solvent indicates the solvent fastness of the pigment. In another method for evaluating […]

3.1.1.3 Solubility Solubility is the most undesirable characteristic of a pigment. Although pigments by definition are insoluble, in practice, many pigments exhibit a minute level of solubility, leading to noticeable problems in the systems in which they are incorporated. Gene­rally, organic pigments exhibit such a level of solubility in organic solvents, while inorganic pigments are […]

A test method for evaluation of tinting strength of colored pigments is briefly described here. A white reduction of the test pigment and another of the reference pigment are prepared by dispersing them separately in the same quantity of suitable solvent-free vehicle with an identical mass ratio of colored pigment to standard white pig­ment. Drawdowns […]

The tinting strength of a colorant is its ability to impart color to a light scattering material by virtue of its absorption properties. Tin­ting strength corresponds to the effectiveness with which a unit quantity of a colorant changes the color of a material. Generally, tin­ting strength is expressed as the mass ratio in which the […]