Hue, lightness, and saturation are the three elements of color, but it is not enough to select plastic colorants only based on the three elements of color. Usually as a plastic colorant, its tinting strength, hiding power, heat resistance, migration resistance, weather resistance, solvent resistance and other properties must also be considered, as well as the interaction of colorants with polymers or additives.
(1) Powerful coloring ability
Colorant tinting strength refers to the amount of pigment required to obtain a certain color product, expressed as a percentage of the tinting strength of a standard sample, and is related to the properties of the pigment and its dispersion. When choosing a colorant, it is generally required to choose a colorant with strong tinting strength to reduce the amount of colorant.
(2) Strong covering power.
Strong hiding power refers to the ability of the pigment to cover the background color of the object when it is applied to the surface of the object. Hiding power can be expressed numerically and is equal to the mass of pigment (g) required per unit surface area when the background color is completely covered. Generally, inorganic pigments have strong covering power, while organic pigments are transparent and have no covering power, but they can have covering power when used together with titanium dioxide.
(3) Good heat resistance.
Heat resistance of pigments refers to the change in color or properties of pigments at processing temperatures. Generally, the heat resistance time of the pigment is required to be 4~10min. Generally, inorganic pigments have good heat resistance and are not easy to decompose at plastic processing temperatures, while organic pigments have poor heat resistance.
(4) Good migration resistance.
Pigment migration refers to the phenomenon that colored plastic products are often in contact with other solids, liquids, gases and other substances, and the pigments migrate from the inside of the plastic to the free surface of the product or the substances in contact with it. Migration of colorants in plastics indicates poor compatibility between colorants and resins. Generally, pigments and organic pigments have high fluidity, while inorganic pigments have low fluidity.
(5) Good light resistance and weather resistance.
Lightfastness and weatherability refer to color stability under light and natural conditions. Light fastness is related to the molecular structure of the colorant. Different colorants have different molecular structures and lightfastness.
(6) Good acid resistance, alkali resistance, solvent resistance and chemical resistance.
Industrial plastic products are often used to store chemicals and transport chemicals such as acids and alkalis, so the acid and alkali resistance of pigments should be considered.