It is precisely because of its own performance characteristics that the masterbatch can stand out among many dyeing materials, and the color can not only last for a long time, but also be very environmentally friendly and safe. However, in some cases, the color of the masterbatch will fade in the short period after use, which is mainly because:
1. Antioxidant properties
Some organic pigments are gradually fading after oxidation due to macromolecular degradation or other changes, one of which is high-temperature oxidation in processing. The second is the oxidation that occurs when encountering strong oxidants (such as chromate in chromium yellow). When the lake and azo pigments are mixed with chrome yellow, the red color gradually fades.
2. Lightfastness
Lightfastness directly affects the fading of products, outdoor products irradiated by strong light, therefore, the lightfastness (lightfastness) grade requirements of masterbatch is an important indicator, and the lightfastness grade is poor, and the product will fade quickly in use. The lightfastness grade of weather-resistant products should not be less than grade 6, it is recommended to choose grade 7 and 8, and indoor products can choose grade 4 and 5.
Solution: The lightfastness of the carrier resin also has a great influence on the color change, and the molecular structure of the resin caused by ultraviolet light changes and fades after irradiation. Black masterbatch manufacturers add light stabilizers such as ultraviolet absorbers to the masterbatch, which can improve the lightfastness of colorants and coloring plastic products.
3. Heat resistance
The thermal stability of a pigment refers to the degree of thermal loss, discoloration, and fading of the pigment at processing temperature. The composition of inorganic pigments is metal oxides and salts, which have good thermal stability and high heat resistance. Pigments of organic compounds will undergo molecular structure changes and a small amount of decomposition at a certain temperature, especially for PP, PA, PET products.
Solution: The processing temperature of the masterbatch is above 280 °C, on the one hand, we should pay attention to the heat resistance of the pigment when selecting the colorant, and on the other hand, we should consider the heat resistance time of the pigment, which usually requires the heat resistance time of 4-10min.
4. Acid and alkali resistance
The fading of colored plastic products is related to the chemical resistance of the colorant (acid and alkali resistance, redox resistance). For example, molybdenum chromium red is resistant to dilute acid, but sensitive to alkali, cadmium yellow is not acid resistant, these two pigments and phenolic resins play a strong reducing role in some colorants, seriously affecting the heat resistance, weather resistance and fading of the masterbatch.
Solution: For the fading of plastic coloring products, the black master manufacturer should comprehensively evaluate the above properties of pigments, dyes, surfactants, dispersants, carrier resins and anti-aging additives according to the processing conditions and use requirements of plastic products.
Therefore, when it is found that the masterbatch is prone to fading after use, it means that the quality of the product is not good, and even the performance is defective. The main reason for fading is the lack of rigor and incorrectness in the production process, so in order to avoid the occurrence of this phenomenon, it is necessary to strictly control the production process and produce in accordance with the correct production method.