Pigments, colorants, whites, blacks

White pigments are used for white coloring and covering, but also for reducing (lightening) colored and black pigments. They must have a minimal intrinsic color tone. 

When colored or black systems are reduced with white pigments, an undertone is observed, which is a particle-size effect of the white pigment (see Section 1.3.1). These undertones can be conveniently expressed as CIELAB color differences. The effects can, however, also be measured by using the difference Rz — Rx between the values obtained with the blue and red tristimulus filters. The undertone measured in this way depends on the lightness, and has a maximum at Y = 41.4. The lightness of a gray paste should therefore have this value to ensure that undertone differences between white pigments are comparable [1.32], [1.33]. 

Colorant A pigment, dye, or other chemical that imparts color (including black and white) or any special effect appearance to a polymer. These special appearances could be metallic, pearlescent, stone and fleck, flourescent, phosphorescent, thermochromatic, or photochromatic. 

Natural black (human hair, bovine eyes) and synthetic (tyrosine, dopa, and dopamine) melanins were investigated by Curie point pyrolysis-gas chromatography-mass spectrometry (86,96). The pigments were characterized by different ratios of degradation products identified as aromatic hydrocarbons, phenols, catechols, pyrroles, and indoles. The amount of ash in karakul lamb wool was correlated to its color, with black producing the most (3.9%) and white the least (1.2%). Similar studies showed a correlation with the calcium content (317,318). 

The creation of Janus particles, with interesting asymmetric electrical properties, was reported by Nisisako et al. [2]. In this case, isobornyl acrylate was used as a hydrophobic, water-insoluble, monomer, and pigmented with carbon black and titanium dioxide as black and white colors, respectively (Figure 14.21). 

Colors - Non-black products are colored by mineral pigments and organic dyes. White articles usually contain titanimn dioxide, alone or supplemented in whole or part by zinc oxide, zinc sulfide, lithopone (precipitated zinc sulfide arium sulfate), or talc. A trace of ultramarine blue is sometimes used to correct off-white tints. Iron oxides are used for colors other than white. 

---