Plastic packaging bag production workers are often questioned by a large number of packaging bag users. Why do some plastic packaging bags fade after being used for a period of time? This makes people want to break their heads and can’t find an answer. Where is the problem? The following yltpacking packaging will give you an analysis. Thermal stability of heat-resistant pigments used in plastic packaging bags: it refers to the degree of thermal weight loss, discoloration and fading of pigments at processing temperatures. Inorganic pigments are composed of metal oxides and salts, and have good thermal stability and high heat resistance. However, pigments of organic compounds undergo molecular structure changes and a small amount of decomposition at a certain temperature. Especially for plastic bag products such as PP, PA and PET, the processing temperature exceeds 280°C. On the one hand, attention should be paid to the heat resistance of the pigment when selecting the colorant. Lightfast colorants directly lead to the fading of plastic packaging bags: For outdoor plastic bag products that are often exposed to strong light, an important indicator of their quality is the lightfastness level of the colorant used. Poor light resistance, plastic bags fade quickly. The light resistance grade of plastic bags commonly used outdoors should not be lower than grade 6, and grade 4 or grade 5 can be selected indoors. The light resistance of the carrier resin also has a great influence on the color change, and the molecular structure of the resin will change and fade after being exposed to ultraviolet light. Adding light stabilizers such as UV absorbers to the masterbatch can improve the light resistance of colorants and colored plastic bags. Oxidation resistance of plastic packaging bag materials: some organic pigments used in plastic packaging bags will undergo macromolecular degradation or other changes, and gradually fade after oxidation. The first is high-temperature oxidation during processing, and the second is oxidation with strong oxidants. For example, when lakes, azo pigments, and chrome yellow are mixed, the red color will gradually decrease. The fading of plastic packaging bags is also related to the chemical properties of the colorant: the chemical resistance of the colorant (acid and alkali resistance, oxidation resistance, and reduction) will cause the acid-base colored plastic packaging bag to change color. For example, molybdate red is resistant to dilute acids, but is sensitive to alkalis, 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 affect the heat resistance, weather resistance and fading of the colorant. The fading of plastic packaging bags is affected by many factors. According to the processing conditions and use requirements of plastic bag products, before producing qualified plastic bags and plastic bag products, the required pigments, dyes, surfactants, dispersants, carrier resins and Performance of anti-aging additives.
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