Texture of pigments (dispersibility)

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 highest potential of pigments in coatings can be realized if their agglomerates are broken and dispersed as primary particles. In the paint manufacturing process, the pigment dispersion step is the most energy-intensive one, and hence ease of pigment dispersion is a desirable property of pigments.

Easily dispersing pigments are called soft-textured pigments, normally dispersing pigments are called normal-textured pig­ments and those that pose difficulty in dispersion are called hard — textured pigments. The pigment texture can be related to its packing and surface area, which are related to particle size and particle shape. Finer and more compacted pigments are more dif­ficult to disperse than coarser and less densely aggregated ones.

Many pigments are surface treated by the manufacturers to enhance their ease of dispersion. Common types of surface treatment include adsorption of an organic or inorganic layer on the pigment surface to modify surface polarity and hence surface energy.

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