Plastic PVC coloring products affected by a variety of factors will occur fade.
The fading of plastic coloring products is related to the light resistance, oxygen resistance, heat resistance, acid and alkaline resistance of the toner and the properties of the resin used.
The following is a detailed analysis of the fading factors in plastic coloring:
1. Light resistance of colorants
The light resistance of the colorant directly affects the fading of the product. For outdoor products exposed to strong light, the light resistance (light resistance) grade requirement of the colorant used is an important index. The light resistance grade is poor, and the product will fade quickly in use.
Weather resistant products to choose the light level should not be lower than six, it is best to choose seven, eight, indoor products can choose four, five.
The light resistance of the carrier resin also has a great influence on the color change, and the molecular structure of the resin changes and fades after uv irradiation.
Adding uv absorbent and other light stabilizers into the base material can improve the light resistance of colorants and colored plastic products.
2. Heat resistance
The thermal stability of heat-resistant pigments is the degree of thermal weight loss, discoloration and discoloration of pigments at the processing temperature.
Inorganic pigments are composed of metal oxides and salts with good thermal stability and high heat resistance.
Organic pigments, on the other hand, undergo molecular structure changes and a small amount of decomposition at a certain temperature.
Especially PP, PA, PET products, the processing temperature of more than 280℃, in the selection of colorant on the one hand to pay attention to the heat resistance of the pigment, on the other hand to consider the heat resistance of the pigment time, usually requires the heat resistance of 4-10min.
3. Antioxidant
After oxidation, some organic pigments gradually fade due to the degradation of macromolecules or other changes. This process is the oxidation of high temperature during processing and the oxidation of strong oxidants (such as chromate root in chromium yellow).
The red color will gradually decrease when the color lake, azo pigment and chrome yellow are mixed.
4. Acid and alkaline resistance
The color fading of 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 acid, but sensitive to alkali, and cadmium yellow is not resistant to acid. These two pigments and phenolic resin have a strong reduction effect on some colorants, seriously affecting the heat resistance and weather resistance of colorants and causing discoloration.
For the fading of plastic coloring products, it is necessary to evaluate the above properties of pigment, dye, surfactant, dispersant, carrier resin and anti-aging agent comprehensively according to the processing conditions and use requirements of plastic products.
