Four major causes of plastic EVA kits fading

I believe that many people are very worried about the discoloration of plastic EVA tool kits. So what causes the tool kits to fade? The discoloration of plastic colored products is related to the light resistance, oxygen resistance, heat resistance, acid and alkali resistance of the pigments and dyes, and the characteristics of the resin used. Let us briefly analyze the following:
1. The fading of acid- and alkali-resistant colored plastic products is related to the chemical resistance of the colorant (acid-alkali resistance, oxidation-reduction resistance).
For example, molybdenum chromium red is resistant to dilute acids, but sensitive to alkalis, and cadmium yellow is not resistant to acids. These two pigments and phenolic resins have a strong reducing effect on some colorants, which seriously affects the heat resistance and weather resistance of the colorants and discoloration occurs.
2. Oxidation resistance Some organic pigments gradually degrade after being degraded by macromolecules or other changes after oxidation.
This process is one of high temperature oxidation during processing, and the other is oxidation in the presence of strong oxidants (such as chromate in chrome yellow). After the use of lakes, azo pigments and chrome yellow, the red will gradually decrease.
3. The thermal stability of the heat-resistant pigment refers to the degree of thermal weight loss, discoloration and discoloration of the pigment at the processing temperature.
The composition of inorganic pigments is metal oxides and salts with good thermal stability and high heat resistance. The pigments of organic compounds undergo molecular structure changes and a small amount of decomposition at a certain temperature. Especially for PP, PA, PET products, the processing temperature is above 280 ° C. On the one hand, when choosing colorants, we must pay attention to the heat resistance of the pigment, on the other hand, we must consider the heat resistance time of the pigment. Generally, the heat resistance time is 4-10rain. .
4. Lightfastness of lightfast colorants directly affects the fading of products.
For outdoor products exposed to strong light, the light resistance (lightfastness) level of the colorant used is an important indicator. The light resistance level is poor, and the product will fade quickly in use. The weather resistance products should be selected not less than six, light grades seven and eight, indoor products can choose four or five. The light resistance of the carrier resin also has a large effect on the change of color, and the molecular structure of the resin caused by ultraviolet radiation changes and fades. Adding light stabilizers such as ultraviolet absorbers to the masterbatch can improve the light resistance of colorants and colored plastic products.