Published: Jan 2012
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CERAMIC PIGMENTS ARE COMPLEX MIXTURES of oxygen-containing materials that have been calcined at high temperatures to form specific crystalline phases . In most cases, oxide raw materials are carefully mixed and then calcined in either batch kilns or continuous calciners . After calcination, they are ground to the necessary fineness in mills. Micronizers and/or jet mills are used to break agglomerates. The final production step involves careful control of the color tone. Because these pigments are formed at high temperatures, they generally offer superb thermal stability and are relatively inert. This results in excellent weathering and light fastness properties. Most of these pigments have superior acid and alkali resistance. They are nonmigrating and nonbleeding in nature and do not interact with polymer systems . The principal disadvantage of ceramic pigments is their low tinting strength. In addition, some are relatively high in cost. This is particularly true with cobalt-containing pigments. Some of these pigments are difficult to disperse. However, the recent development of easily dispersed ceramic pigments should eliminate this problem. A final concern is the inherent hardness of these pigments. Their hardness can lead to processing system damage through abrasion. When using ceramic pigments, processing system components designed for use with abrasive materials should be considered.
Eppler, Richard A.
Eppler Associates, Cheshire, CT