5 сентября, 2015 
Pokraskin There are three groups of commercially important ferrite and chromite browns. The first are pure ferrites defined by C. I. Pigments Brown 11, Brown 31, and Yellow 119, followed by the mixed chromite/ferrite browns which are C. I. Pigments
Brown 33 and Brown 35. These are all spinels. The third type is mixed chromium iron pigments. These pigments adopt either the hematite or the corundum structures.
Pure ferrite spinels containing zinc, C. I. Pigments Yellow 119 and Brown 31, or magnesium, C. I. Pigment Brown 11, provide light yellow-brown to light red — brown colors. Zinc ferrites, and to a lesser extent magnesium ferrites, are widely used as heat-stable colorants for thermoplastics.
The mixed chromite/ferrite spinels, C. I. Pigments Brown 33 and Brown 35, provide darker browns than the pure ferrites, covering the color range from reddish — brown to nearly black. These products are used mainly in plastics and coatings to provide heat stable colors. In addition, Brown 35 spinels have good IR-reflective properties, and are used in low heat build-up plastics and coatings.
Pigments containing only iron(III) and chromium(III) oxides in an M2O3 stoichiometry are identified as either C. I. Pigment Green 17 or C. I. Pigment Brown 29. Both of these Colour Index descriptions denote the same pigment type, and the names can be used interchangeably. The pigments are not spinels, as they adopt either the corundum or hematite structures. They are dark red-brown to nearly black in color.
The great feature of these pigments is their good IR reflectivity. They generally have higher IR reflectivity than other dark IR-reflective CICPs, as demonstrated in Figure 5.5. These browns and blacks are primarily used to prepare dark exterior durable colors with low heat build-up.
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