Plastic colored products will fade due to many factors. The fading of plastic colored products is related to the light resistance, oxidation resistance, heat resistance, acid and alkali resistance of the color powder and the characteristics of the resin used. The following is a detailed analysis of the factors that cause plastic coloring to fade:

1. Light resistance

The light resistance of the colorant directly affects the fading of the product. For outdoor products exposed to strong light, the light resistance (sun resistance) level requirement of the colorant used is an important indicator. If the light resistance level is poor, the product will fade quickly during use. The light resistance level of weather-resistant products should not be lower than level 6. preferably level 7 or 8. and level 4 or 5 can be selected for indoor products. The light resistance of the carrier resin also has a great influence on the change of color. After the resin is irradiated by ultraviolet rays, its molecular structure changes and fades. Adding light stabilizers such as ultraviolet absorbers to the masterbatch can improve the light resistance of the colorant and colored plastic products.

2. Heat resistance

The thermal stability of the pigment refers to the degree of thermal weight loss, discoloration and fading of the pigment at the processing temperature. Inorganic pigments are composed of metal oxides and salts, with good thermal stability and high heat resistance; while organic compound pigments will undergo molecular structure changes and decomposition at a certain temperature. Especially for PP, PA, and PET products, the processing temperature is above 280°C. When selecting colorants, attention should be paid to the heat resistance of the pigment on the one hand, and the heat resistance time of the pigment on the other hand, which is usually required to be 4-10 minutes.

3. Antioxidation

Some organic pigments gradually fade due to macromolecular degradation or other changes after oxidation. This process is one of high-temperature oxidation during processing and the other is oxidation caused by strong oxidants (such as chromate in chrome yellow). After the color lake, azo pigments and chrome yellow are mixed, the red color will gradually fade.

4. Acid and alkali resistance

The fading of colored plastic products is related to the chemical resistance (acid and alkali resistance, oxidation and reduction resistance) of the colorant. For example, molybdenum chromate red is resistant to dilute acid but sensitive to alkali, and cadmium yellow is not resistant to acid. These two pigments and phenolic resin have a strong reducing effect on some colorants, which seriously affects the heat resistance and weather resistance of the colorant and causes fading.

For the fading of plastic colored products, the above-mentioned properties of the required pigments, dyes, surfactants, dispersants, carrier resins and anti-aging additives should be comprehensively evaluated according to the processing conditions and use requirements of the plastic products before they can be selected.