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[1] [2] Pigments support a structure of fine porosity and form a light scattering surface. The surface charge of the pigment plays an important role in dispersion consistency. The surface charge of calcium carbonate is negative and not dependent on pH , however it can decompose under acidic conditions. [ 3 ]
Dispersion is a process by which (in the case of solid dispersing in a liquid) agglomerated particles are separated from each other, and a new interface between the inner surface of the liquid dispersion medium and the surface of the dispersed particles is generated. This process is facilitated by molecular diffusion and convection. [4]
The chief purpose of pigment dispersion is to break down aggregates and form stable dispersions of optimally sized pigment particles. This process generally involves three distinct stages: wetting, deaggregation, and stabilization. A surface that is easy to wet is desirable when formulating a coating that requires good adhesion and appearance.
Next there is a fusion of the frit to the substrate and pigments followed by the expulsion of voids to give a compacted structure. Lastly there is a formation of a surface with the desire properties. A successful firing of the glass and ceramic ink will result in a bubble free layer of constant thickness and homogeneous pigment dispersion ...
Determining the fineness of a paint's grind is important, because too coarse a grind may reduce the paint's color uniformity, gloss, and opacity. [7] The Hegman gauge is widely used for this purpose because it requires minimal skill and only a few seconds' work.
The pigment preparations are produced in batches. For this the formulation components are distributed into a binder previously selected for the respective application and then dispersed. The most optimal breaking up of agglomerates is crucial to ensure a high effectiveness of the colour concentrates and / or functional process additives.
Mixing is implemented at low rate for adequate dispersion. During the mixing, there is no air added into the mixture. In the second phase, pigment is in the process. It will be added in suitable amount into the water. Mixing is implemented at very high rate in this process which is different from the first phase.
Pigments for sale at a market stall in Goa, India. A pigment is a powder used to add color or change visual appearance. Pigments are completely or nearly insoluble and chemically unreactive in water or another medium; in contrast, dyes are colored substances which are soluble or go into solution at some stage in their use.