Some people have encountered such a situation. The game controller case faded gratuitously after a long time. You thought it was not a material that would fade, but it is. Then let’s take a look at the cause of the fading.

The factors cause the fading of plastic EVA products. 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 characteristics of the resin used. According to the processing conditions and use requirements of plastic products, the required pigments, dyes, surfactants, dispersants, carrier resins and anti-aging additives must be selected after comprehensively evaluating the above properties in the production of masterbatch.

1. The fading of acid and alkali resistant 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 alkali, and cadmium yellow is not acid resistant. These two pigments and phenolic resin have a strong reducing effect on some colorants, which seriously affect the heat resistance and weather resistance, then leading to fade.

2. Antioxidant properties. Some organic pigments will gradually fade due to degradation of macromolecules or other changes after oxidation.

This process: one is high temperature oxidation during processing, and the other is oxidation when encountering strong oxidants (such as chromate in chrome yellow). After mixed use of lake, azo pigment and chrome yellow, the red color will gradually fade.

3. The thermal stability of a heat-resistant pigment refers to the degree of thermal weight loss, discoloration and fading of the pigment at the processing temperature.

Inorganic pigments are composed of metal oxides and salts with good thermal stability and high heat resistance. The pigments of organic compounds will 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℃. When selecting colorants, we should not only pay attention to the heat resistance of the pigment, but also consider the heat resistance time of the pigment. Generally, the heat resistance time is 4-10 minutes.