Pigment Blacks for Plastics

Unlike other pigments, carbon black used in plastics does not only yield coloristic effects but also modifies the electrical properties, provides heat and UV resistance, and may act as a filler to modify mechanical properties. 

Carbon black is used in large amounts for the black and gray tinting of plastics, including polyethylene, polypropylene, polyvinyl chloride, polystyrene, ABS polymers, and polyurethanes. The largest application in tonnages is in polyolefins. Pelletized black is usually employed. 

Carbon black concentrations of 0.5-2% are required for full-tone tinting. For crystal-clear plastics, the addition of up to 1% carbon black is generally sufficient. Plastics with marked intrinsic color, e.g. ABS, are tinted with blacks of higher tinting 

Strength at concentrations of 1-2%. Transparent tints have black contents of 0.02-0.2%. 

Most of the carbon black used in the plastics industry is produced by the furnace black process. Fine furnace blacks often appear more bluish in incident Ught (fuU-tone tinting) than coarse ones, but more brownish in transmitted Ught (transparent tinting) and in gray tints. By controUing the conditions of black manufacture, however, substantial shifts in hue can be achieved. Bluish carbon blacks are commonly preferred to achieve the impression of greater color depth. 

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Pigment Blacks for Plastics, Degussa Technical Bulletin No. 40, Frankfurt am Main (1998). 

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