One: Acid and alkali resistance

The fading of blow-molded products is often due to the chemical resistance of the coloring agents, such as molybdenum chromite which resists dilute acids but is reactive to alkalis, and cadmium yellow which is not resistant to acids, severely affecting the coloring effect of the agents and triggering fading.

Thermal Resistance

This is quite straightforward to understand. Heat resistance refers to the degree of discoloration and fading that occurs in pigments under high temperatures. For coloring agents, organic pigments will change their molecular structure under high temperatures, leading to fading; whereas inorganic pigments are relatively more heat-resistant and more stable.

Three: Lightfastness

The poor lightfastness of coloring agents can directly lead to fading. Many blow-molding products are outdoor items, thus lightfastness is a top requirement. Industry standards generally dictate that outdoor products must have a lightfastness rating of at least 6, while indoor products typically choose a rating of 4-5.

Four: Antioxidant Properties

Some inorganic pigments gradually fade due to the dissolution of macromolecules or other modifications after oxidation. This process occurs primarily during high-temperature oxidation in the production and processing phase, as well as upon contact with strong oxidizing agents. When used in a mixed application with mordant yellow and formamide dye paste, the red color will gradually diminish.