Types of Pigments

Several new types of pigments have been introduced commercially which are based on polymers that do not contain formaldehyde. These pigments have some different characteristics but have the advantage of not giving off formaldehyde. Most of the primary manufacturers provide these types of pigments and more are being developed. 

The reaction of dextrose with a nitrogen-containing compound, eg, amino acids or proteins, yields a series of intermediates which form pigments of varied molecular weight (Maikard reaction). The type of pigments produced is dependent on reaction conditions such as pH, temperature, and concentration of reactants. 

The energy required to initiate an explosion and the maximum explosive pressure developed by a number of polyester—epoxy powder coatings has been studied in some detail (89). The variables studied included composition, level and type of pigmentation, particle size, and concentration in air. The lowest MEG for unfilled and unpigmented powders was 33—35 g/m. ... 

The hue of the colorant varies gready with the amount and type of pigment found in the fish scales. Carotenoids produce reds and yellows, melanin results in blacks, and combinations of guanine and melanin produce greens and blues. Only when guanine is found alone is the product silvery or peady white. 

Metallic, pearlescent and fluorescent pigments are grouped together in this section as three types of pigment used for their ability to produce unusual optical effects. 

This type of pigment is the precipitate formed when molybdic oxide is dissolved in aqueous sodium hydroxide with the addition of sodium chromate. The resulting mixture is reacted with a solution of lead nitrate. The precipitate formed is further processed through filtration, washing, drying, milling, and packaging. 

Scierka et al. [93] reported on the difference in chemical changes, as studied by XPS, in an epoxy system with and without TiC>2 pigment. Whereas the concentration of the pigment seemed to have no influence, the type of pigment... 

Funk C, Schroder WP, Napiwotzki A, Tjus SE, Renger G, Andersson B. The PS 11 -S protein of higher plants A new type of pigment binding protein. Biochemistry 1995 34 11,133-11,141. 

However, instead of exploring new pigments, it is often preferable to optimize the properties of one of the already available compounds. This explains why a given type of pigment is often marketed in more than one physical form to provide a variety of coloristic and application properties, each of which is designed for a specific vehicle system or condition of use. 

P.R.214 affords a medium to bluish shade of red. It exhibits average stability to organic solvents, an aspect in which it resembles other members of its class. P.R.214 is very lightfast and fast to overcoating. Its weatherfastness, however, does not quite reach the standards of other types of pigments within its class it is somewhat inferior, for instance, to that of P.R.242. 

The shortage of tungsten and molybdenum during the 1930s in Germany necessitated the use of copper ferrocyanide as anion. Some of these salts have maintained their commercial position to the present time. Besides, silicomolybdates are also used to produce this type of pigments. 

Scotopic vision does not permit the resolution of colors. Rods are much more sensitive to dim light (see Figure 1.3) than cones, but they do not have different types of pigments that are sensitive to different wavelengths so color cannot be distinguished in dim lighting conditions. 

Commelinaceae) shows an extra absorption band at 583 nm at pH values above 4.0, which makes this pigment highly colored at these pH values.The high stability of this type of pigments with as much as four acyl units was assumed to be due to the difficulty of water molecule diffusion to the hydrophobic center formed by the acyl groups and the aglycone. 

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