Opacity and tinting strength

Key criteria for all pigments (and particularly whites) are opacity and tinting strength. 

Opacity is particularly important in thin-section applications, where a highly opaque pigment can serve well, even at a lower concentration. In thicker sections it may be less important - but it is as well to remember the other side of the coin lower concentrations of Ti02 pigment may detract from durability. 

With titanium dioxide, the development of opacity and tinting strength depends on light-scattering power, which is governed by refractive index, particle size distribution, Ti02 content, and dispersion in the polymer. 

The effect on properties of particle size distribution of titanium dioxide is  

The actual Ti02 content of a pigment is an important factor in the opacity developed by a specific pigment. Typical grades have a content of 8 8-9 7%. 

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They have good opacity and tinting strength. Lead chromates with lead sulfate are used to provide rays of color from pale primrose to scarlet. They are economical and have inhibitive properties largely used in automotive coatings. 

P. D. Mitton, "Opacity, Hiding Power, and Tinting Strength," in Printing Ink Handbook Vol. Ill, T. C. Patton, editor, John Wiley Sons, New York, 1973, p. 289-339 J. W. Vanderhoff, "Rheology and Dispersion of Printing Inks, " ibid., p. 409-416. 

Ultramarine blue has poor opacity but high tinting strength, high heat resistance, and good alkali resistance. It is primarily used as a tinting color, and when added to whites makes them look whiter by giving them a bluish cast. 

A high quality pigment grade with excellent whiteness, high opacity and high tinting strength. 

Fillers may also play the role of a pigment and when they do, the particle size distribution is important for several reasons. Figure 5.9 shows that the tint strength and opacity depend particle size. This graph is based on the following relationship developed Irom the scattering theory of Mie ... 

The use of fluorescent pigments and colorants in plastics applications has experienced sustained growth over the past few decades. Research and development efforts continue in the pursuit of more thermally stable, plate-out resistant fluorescent colorants with greater tinting strength and opacity. As these qualities are achieved and improved upon, we should see the use and growth of fluorescent pigments and colorants into more diverse plastics applications well into the future. 

Pigment Violet 19 (Red) is also offered with variety of properties and comes in a variety of shades and opacities. The more opaqne have better lightfastness and heat stability and the more transparent have excellent tinting strength. Some recently developed products can offer both. The particle size and particle size distribution are mainly responsible for the variety of products offered. Most grades are FDA approved. 

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