Factors affecting the fading of plastic products
According to the data and practice, it has been proved that there are many factors affecting the fading of plastic products. The fading of plastic colored products is related to the light resistance, oxidation resistance, heat resistance, acid and alkali resistance of pigments and dyes and the characteristics of the resin used. In masterbatch, the above properties of pigments, dyes, surfactants, dispersants, carrier resins and anti-aging additives can be comprehensively evaluated before they can be selected. The following are the common reasons that affect product discoloration for reference.
The light resistance of colorants directly affects the fading of plastic products. 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 in use. So this is why, for example, the anti-glare panels on the highway, water horses, etc., after a few years of use, the color of the sun exposure will fade. However, in general, during blow molding, quantitative anti-UV ingredients will be added to ensure the durability of the product color retention time.
2. Heat resistance
The thermal stability of pigments refers to the degree of thermal weight loss, discoloration and fading of pigments at processing temperature. The components of inorganic pigments are metal oxides and salts, which have good thermal stability and high heat resistance. The organic compound pigments will undergo molecular structure changes and a small amount of decomposition at a certain temperature. In fact, we need in the production process. If it is a plastic product that requires high temperature heating, we need to choose a more heat-resistant pigment to ensure the color. Discoloration, fading, to ensure the overall appearance of the product.
Some organic pigments gradually fade due to the degradation of macromolecules or other changes after oxidation. The first process is high temperature oxidation during processing. The second is the oxidation of strong oxidants (such as chromate in chrome yellow), and the red color will gradually decrease after the mixed use of lakes, azo pigments and chrome yellow.
4. Acid and alkali resistance
The fading of colored plastic products is related to the chemical resistance (acid and alkali resistance, redox resistance) of colorants, such as molybdenum-chromium red, which is resistant to dilute acid, but is sensitive to alkali, and cadmium yellow is not acid-resistant. These two kinds of pigments and phenolic resin have a strong reducing effect on some colorants, which seriously affects the heat resistance, weather resistance and fading of the colorants.