In daily life, colorful plastic products are ubiquitous and enrich our lives. At the same time, the problem of plastic fading has also become a problem. The fading of colored plastic products is related to the heat resistance, light resistance, acid and alkali resistance of the colorant, and the characteristics of the resin used.
Heat resistance means that there is no obvious change of shade, coloring power and performance under a certain processing temperature and a certain time. Colorants often decompose when heated during plastic molding, resulting in color changes. Generally, inorganic pigments have good heat resistance, but organic pigments and dyes have different heat resistance. Among the organic pigments that can remain stable at high temperatures, the most widely used are phthalocyanine green, phthalocyanine blue, carbazole violet, quinacridine red, isoindolinone yellow, and perylene red. Therefore, it is particularly important to select the appropriate colorant based on the heat resistance index.
1.Light resistance :
The definition of lightfastness refers to the ability of colorants and polymer systems to maintain their color when exposed to sunlight. The main reason for the changes in colorants and sunlight is the damage caused by ultraviolet rays and visible rays in sunlight to colored products.
The lightfastness index is judged as an 8-level system, with the 8-level being the best and the 1-level being the worst.
The importance of light resistance varies depending on its use, and sometimes it is extremely important, such as outdoor building boards, billboards and car taillights. In these products, it is hoped that the products can be exposed to full sunlight for at least ten years keep it steady.
3.Acid and alkali resistance：
The fading of colored plastic products is related to the chemical resistance of the colorant (acid and alkali resistance, oxidation-reduction resistance). For example, molybdenum chrome red is resistant to dilute acid, but is sensitive to alkalis, and cadmium yellow is not acid resistant. These two pigments and phenolic resins have a strong reducing effect on certain colorants, which seriously affects the heat resistance and weather resistance of the colorants and causes fading.
For the fading of plastic colored products, it should be selected according to the processing conditions and use requirements of the plastic products, after comprehensive evaluation of the above-mentioned properties of the required colorant surfactants, dispersants, carrier resins and anti-aging additives.