With Flying Colors: Pigment Size Analysis using Dry Jet Dispersion Technology

In the paint and coating industry, the particle size of pigments critically affects the optical properties, viscosity and stability of the finished products. The PSA measures the particle size of dry (powder) samples using laser diffraction. Its patented dry jet dispersion technology enables optimal dispersion of powder under low air pressure, a feature of particular interest for the analysis of pigments which are fragile by nature. Here we show that the PSA was able to disperse and measure a pigment powder using an air pressure of only 200 millibars without damaging the particles.

Pigments are natural or synthetic, organic or inorganic substances capable of absorbing parts of the light spectrum, and re-emitting part of this light, which corresponds to the color perceived by the eye. 

The particle size of pigments has an immense effect on their optical properties, coating performance, rheological properties and stability. Furthermore, the particle size of pigments also affects the final appearance of the coated surface. Paint sheen (or glossiness) depends on how deep the pigment particles are immersed in the binder, and it can be anywhere between glossy and matt. Furthermore, the ability of a pigment to absorb light, i.e., its color intensity, increases as particle size decreases and the specific surface increases, until a size at which the particles become translucent.

Even though small particles lead to a more resistant glossy finish and a more intense color, they also exhibit a higher "chalking" effect. This effect can be described as a layer of dust that comes off the paint finish, and is characteristic of coating aging. Other paint attributes that are influenced by the particle size distribution (PSD) are the rheological properties. Thus, particle size affects production (e.g. viscosity is increased by small particles) as well as application (flow and adhesion).

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