Four major reasons for the fading of plastic EVA tool bags

I believe many people are very worried about the fading problem of plastic EVA tool bags, so what causes the tool bags 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, and the properties of the resin used. Let’s briefly analyze it below.

1. 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 acids, but is sensitive to alkali, and cadmium yellow is not acid-resistant. These two pigments and phenolic resin have a strong reducing effect on certain colorants, seriously affecting the heat resistance and weather resistance of the colorants and causing fading.

2. Antioxidation: Some organic pigments gradually fade due to degradation of macromolecules or other changes after oxidation.

This process involves high-temperature oxidation during processing and oxidation when encountering strong oxidants (such as chromate in chromium yellow). When lakes, azo pigments and chrome yellow are mixed, the red color will gradually fade.
3. Thermal stability of heat-resistant pigments refers to the degree of thermal weight loss, discoloration, and fading of the pigment under processing temperature.

Inorganic pigments are composed of metal oxides and salts, which have good thermal stability and high heat resistance. Pigments made from 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, on the one hand, we must pay attention to the heat resistance of the pigment, and on the other hand, we must consider the heat resistance time of the pigment. The heat resistance time is usually 4-10rain. .

4. Lightfastness The lightfastness of colorants directly affects the fading of products.

For outdoor products that are exposed to strong light, the lightfastness (sunfastness) level of the colorant used is an important indicator. If the lightfastness level is poor, the product will fade quickly during use. The light resistance grade selected for weather-resistant products should be no less than level six, and it is best to choose levels seven or eight. For indoor products, level four or five can be selected.

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 ultraviolet absorbers to the masterbatch can improve the light resistance of colorants and colored plastic products.