A substance that can change the color of an object, or that can color an object that is originally colorless, is generally called a colorant. The colorant produces a color by selectively absorbing and reflecting some of the colored light waves. Compared with traditional habits, plastic colorants can be divided into two major categories of dyes and pigments.
Dyes are organic compounds that are soluble in most solvents and dyed media. It is characterized by good transparency in plastics, strong coloring power and low relative density. Pigments are different from dyes. Pigments are colored substances that are insoluble in water, oil, resin, etc., and are usually present in a dispersed state in plastics, so that these products exhibit different colors. Contrary to the dye, the pigment and the material to be colored by it. There may be no affinity, so in order to obtain the desired coloring performance, it is necessary to mechanically disperse the pigment evenly in the plastic.
Dyes are organic in structure, while pigments may be organic or inorganic. The properties of these two types of pigments vary greatly from each other. Inorganic pigments are metal oxides and metal salts, and inorganic pigments of the same type have much in common. Inorganic pigments are insoluble in common solvents and have better heat resistance than organic pigments. On the other hand, organic pigments generally have higher tinting strength than inorganic pigments.
Comparison of various colorant properties applied to plastics
Performance Index | Organic Pigments | Inorganic Pigments | |
Chromatographic Range | Wide | Narrow | Wide |
Colouration | Bright | Not Bright | Bright |
Tinting Strength | Higher | High | Highest |
Light/Weather Resistance | Higher | Highest | High |
Migration Resistance | Better | Best | Good |
Dispersion Property | Good | Better | No need to disperse |
Heat Resistance | Higher | Highest | Higher |
It can be seen from the table that the organic pigments applied to plastics have bright color, for example: organic pigment benzidine yellow G, permanent yellow 2GS, permanent yellow HR, red lake C, fast scarlet BBN, brilliant red 2BP, Pigment Red 254, Permanent Orange G, etc., used in plastic products, with bright color, good migration resistance, good product stability, easy dispersion, low filtration value, and superiority of other pigments.
