Coloring products are discolored by a variety of factors, and the discolouration of colored plastic products is related to the lightfastness, oxygen resistance, heat resistance, acid and alkali resistance, and the properties of the resin used.
The following is a detailed analysis of the fading factors in plastic coloring:
1. Light fastness of colorant
The light resistance of the colorant directly affects the fading of the product. Outdoor products subject to strong light irradiation, the light resistance (lightfastness) grade requirement of the colorant used is an important index, and the light resistance is poor, and the product will quickly fade during use. The selected light level should not be less than six, the best selection of seven, eight, indoor products optional four or five.
The light resistance of the carrier resin also has a greater impact on the color change, the molecular structure of the UV-induced resin changes fading.With the addition of UV absorbers and other light stabilizers in the masterbatch can increase the colorants and colored plastic products Lightfastness.
2. Heat resistance
Heat-resistant pigment thermal stability refers to the processing temperature of the paint weight loss, discoloration, fading extent.
Inorganic pigment composition of metal oxides, salts, thermal stability, heat resistance, while the organic compounds of the pigment at a certain temperature will occur molecular structure changes and a small amount of decomposition, especially PP, PA, PET products , The processing temperature is above 280 ℃. On the one hand, when selecting the toner, we should pay attention to the heat resistance of the pigment. On the other hand, we should consider the heat-resistant time of the pigment, and usually require the heat-resistant time is 4-10min.
3. Antioxidant
Some of the organic pigments undergo macromolecular degradation or other changes that gradually fade after oxidation, a process of high temperature oxidation during processing, and second, oxidation of strong oxidants such as chromate in chrome yellow. , Azo pigments and chrome yellow mixed use, the red will gradually diminish.
4. Acid and alkali resistance
Fading of colored plastic products is related to the chemical resistance (acid and alkaline resistance, oxidation-reduction resistance) of colorants, such as molybdenum-chromium-red resistance to dilute acids but to alkali, and cadmium yellow, which are not acid- Resins act strongly on certain colorants, severely affecting colorant heat resistance, weatherability and discoloration.
Faded plastic coloring products, plastic products should be based on processing conditions and requirements, the required pigments, dyes, surfactants, dispersants, carrier resins and anti-aging additives, a comprehensive assessment of the above properties before use.