What causes the tool case to fade? The fading of plastic colored products is related to the light resistance, oxygen resistance, heat resistance, acid and alkali resistance of pigments and dyes, as well as the characteristics of the resins used. Below, we will briefly analyze and analyze.
1. The fading of acid and alkali resistant colored plastic products is related to the chemical resistance (acid and alkali resistance, oxidation and reduction resistance) of the colorant.
"For example, molybdenum chrome red is resistant to dilute acids, but is sensitive to alkali, and cadmium yellow is not resistant to acids. These two pigments and phenolic resins have a strong reducing effect on some colorants, seriously affecting their heat resistance, weather resistance, and discoloration.".
2. Oxidation resistance Some organic pigments undergo macromolecular degradation or other changes after oxidation and gradually fade.
EVA Case
This process involves both high-temperature oxidation during processing and oxidation in the presence of strong oxidants such as chromate in chrome yellow. After mixing lakes, azo pigments, and chrome yellow, the red color gradually decreases.
3. The thermal stability of heat resistant pigments refers to the degree of thermal weight loss, discoloration, and discoloration of pigments at processing temperature.
Inorganic pigments are composed of metal oxides and salts, with good thermal stability and high heat resistance. Organic compound pigments, on the other hand, 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 ℃. 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. Generally, the heat resistance time is required to be 4-10 minutes.
4. The light fastness of colorants directly affects the fading of products.
For outdoor products exposed to strong light, the light resistance (light resistance) grade requirement of the colorant used is an important indicator. Due to poor light resistance, the product will quickly fade during use. The light resistance level selected for weather resistant products should not be lower than Level 6. For Zui products, Level 7 and Level 8 should be selected, while for indoor products, Level 4 and Level 5 can be selected.
The light resistance of the carrier resin also has a significant impact on the color change. After UV irradiation, the molecular structure of the resin changes and fades. Adding light stabilizers such as ultraviolet absorbers to the masterbatch can improve the light resistance of colorants and colored plastic products.