The light fastness of the colorant of acrylic products directly affects the fading of the product. For outdoor products exposed to strong light, the light fastness (light fastness) grade requirement of the colorant used is an important indicator. The light fastness grade is poor, and the product will fade quickly during use. . The light resistance grade selected for weather-resistant products should not be lower than grade 6, preferably grade 7 or grade 8, and grade 4 or grade 5 for indoor products.
The light resistance of the carrier resin also has a great influence on the color change. After the resin is irradiated by ultraviolet rays, its molecular structure changes and the color fades. Adding light stabilizers such as UV absorbers to the masterbatch can improve the light resistance of colorants and colored acrylic products.
The thermal stability of heat-resistant pigments in acrylic products refers to the degree of thermal weight loss, discoloration and fading of the pigments at the processing temperature. The components of inorganic pigments are metal oxides and salts, which have good thermal stability and high heat resistance. The pigments of organic compounds will undergo changes in molecular structure and a small amount of 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. The heat resistance time is usually required to be 4-10min .
Acrylic products gradually fade due to the degradation of macromolecules or other changes after oxidation of certain organic pigments. This process is one of high temperature oxidation during processing, and the other is the oxidation of strong oxidants (such as chromate in chrome yellow). When lakes, azo pigments are mixed with chrome yellow, the red color will gradually decrease.