Pigment particle size

The energy required to initiate an explosion and the maximum explosive pressure developed by a number of polyester—epoxy powder coatings has been studied in some detail (89). The variables studied included composition, level and type of pigmentation, particle size, and concentration in air. The lowest MEG for unfilled and unpigmented powders was 33—35 g/m. ... 

The specific surface area also represents a mean of the pigment particle size distribution. It can be used to calculate the mean diameter of the surface distribution. Care must be taken that the effect of the internal surface area is taken into account. If the product has an internal surface area which cannot be neglected in comparison to the external surface area, then the measured specific surface area no longer gives a true measure of the mean diameter. This applies, for instance, to aftertreated pigments because the treatment material is often very porous. 

Hardness and Abrasiveness. The abrasiveness of a pigment is not identical to its intrinsic hardness, i.e., the hardness of its primary particles. In practice the Mohs hardness is not therefore a useful indication of the abrasiveness of a pigment. Abrasion rather depends on pigment particle size and shape and is usually caused by the sharp edges of the particles. A standard test procedure for determining abrasiveness does not exist. A method based on the abrasion of steel balls by the pigment is described in [1.12],... 

The opacity of pigments is a function of the pigment particle size and the difference between the pigment s refractive index and that of... 

Colorants are typically defined as pigments and dyes that, when added to plastics, define a specific color. The subject of colorants has been discussed in numerous books and papers. However, in the context of this chapter, a dye is defined as a substance that is soluble in the resin system and produces color only by the absorption of light and no scattering of light. Pigments are not soluble in the resin system and therefore must be mixed into the resin by one of many dispersion processes. Factors such as pigment particle size and ease of mixing or dispersion directly influence their... 

When thermoforming coextruded sheets, the thickness and the viscosity of the upper layer in relation to the pigment particle size and its thickness influence the surface appearance. Of course, the degree of elongation and tight bends are critical. 

The authors determined pigment particle size using Green s photographic method (9) which could not have been too precise, but it was claimed that good correlation had been obtained with the relative hiding power values of Hallet (11) when calculated for film thicknesses, providing a residual contrast of 2% over their black substrate (see Table III). 

Various mills usually do not "grind" or reduce the pigment particle size they disperse the agglomerates. The milling equipment must not only wet and disperse but also be able to move this mass. Consequently, the viscosity of the mill base is important. 

The particle size 75/25 ratio is calculated from the Sedigraph as the measured value of the pigment particle size measured in micrometres at the 75 weight percentile, divided by the particle size measured in micrometres at the 25 weight percentile. 

Further, an inkjet method has been described wherein the inkjet recording material such as paper or plastic comprises a top layer containing core-shell particles of a refractive nature (17). Preferred pigment particle sizes are 0.005-0.3 jum. 

Pigment Particle size [fim] Suijactant Appearance R erences... 

The calculations show that only a very thin colour layer (< 5-7 pm) can be applied so as to adhere, since otherwise the tension threshold is exceeded, leading to chipping off of the composite. This makes it necessary to produce colours that are opaque at such minimum layer thicknesses, which can lead to difficulties in view of pigment particle sizes often exceeding 10 pm. Another difficulty is that the upper cooktop surface of the colours deemed generally suitable for decoration of Ceran cooktops must also withstand other, sometimes extreme, loads. For example, these loads are as follows. 

There are other factors that need to be considered to make up a good paint, including pigment particle size, solubility of the pigment in the medium, media adsorption, reactivity with the medium, etc. There is so much more to color than meets the eye ... 

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