Home / News / Industry News / What are the reasons for the fading of blow molding products

Industry News

What are the reasons for the fading of blow molding products

1. Acid and alkali resistance
The fading of blow mold colored plastic products is related to the acid resistance (corrosion resistance, air oxidation resistance) of the colorant. For example, the red color of molybdenum-chromium is resistant to dilute acid, but it is alkali-sensitive, and the yellow color of cadmium is not acid-resistant. These two pigments and phenolic resin play a strengthening role in a certain colorant, which will fade the heat resistance and weather resistance of the colorant.
2. Heat resistance
The so-called thermal stability means that the pigment cannot be discolored by heat at the processing temperature, and it disappears in the discoloration. The components of inorganic pigments are metal oxides and salts, which have good thermal stability and high heat resistance. The pigments of 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℃. When selecting colorants, on the one hand, pay attention to the heat resistance of the colorant, and on the other hand, consider the heat resistance time of the colorant. Generally, the heat resistance time is required. at 4-10ran.
3. Antioxidant
Some organic pigments gradually fade due to the degradation of macromolecules or other changes after oxidation. This process is one of high temperature oxidation during processing, and the other is the oxidation of strong oxidants (such as chromate in chrome yellow). When the lake, azo pigments and chrome yellow are mixed, the redness gradually decreases.
4. Lightfastness
The light fastness of the product is affected by the fading of the product, and the light fastness grade of the product is an important indicator that affects the light fastness of the product. The light resistance grade selected for weather-resistant products should not be lower than grade six, grade seven or eight, and grade four or five for indoor products. 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. The addition of light stabilizers such as UV absorbers to masterbatches can improve the lightfastness of colorants and colored plastic products.