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What are the factors that affect the fading of plastic crafts?

TIME:2021-04-16 Share

As we all know, plastic colored products will fade due to many factors. This is closely related to the superposition of various factors. The fading of colored plastic products is related to the light resistance, oxygen resistance, heat resistance, acid and alkali resistance of pigments and dyes, and the characteristics of the resin used. This series of associations all hint at the diversity of plastic coloring products. According to the processing conditions and use requirements of plastic products, in any case, the required pigments, dyes, surfactants, dispersants, carrier resins and anti-aging additives can only be comprehensively evaluated in the production of masterbatch. Optional. These conditions are quite harsh.

It can be seen that the lightfastness of general lightfast colorants directly affects the fading of products. For outdoor products exposed to strong light, the lightfastness (lightfastness) level requirements of the colorants used are an important indicator, and the lightfastness has reached a certain level. The light fastness level is poor, and the product will fade quickly in use. In any case, the light resistance grade selected for weather-resistant products should not be lower than six grades, preferably seven or eight grades, and indoor products can choose four or five grades. This should be just right. The light resistance of the carrier resin also has a greater impact on the color change. After the resin is irradiated by ultraviolet rays, its molecular structure changes and the color fades. Adding light stabilizers such as ultraviolet absorbers to the masterbatch can improve the light resistance of the product.

Over time, the thermal stability of heat-resistant pigments refers to the degree of thermal weight loss, discoloration, and fading of the pigment at the processing temperature. Inorganic pigments are composed of metal oxides and salts, with good thermal stability and high heat resistance. This is an explanation of a general law. The pigments of organic compounds will undergo molecular structure changes and a small amount of decomposition at a certain temperature. The self-decomposition of these pigments is more serious, especially for PP, PA, PET products, and the processing temperature is above 280℃. When selecting colorants, one should pay attention to the heat resistance of the pigment and the heat resistance time of the pigment, which is usually required. The heat-resistant time must be long enough;.

There are also some fading situations. Anti-oxidation Some organic pigments undergo macromolecular degradation or other changes after oxidation and gradually fade. This process is high temperature oxidation during processing, and oxidation occurs when encountering strong oxidants. After the lake, azo pigment and chrome yellow are used in combination, the red color will gradually fade. This is the effect of strong oxidants. The fading of acid and alkali resistant colored plastic products is related to the chemical resistance of the colorant. This is a combination of things that are inevitable. For example, molybdenum chrome red is resistant to dilute acid, but is sensitive to alkalis, and cadmium yellow is not acid resistant. These two pigments and phenolic resins have a strong reducing effect on certain colorants and challenge heat resistance.

We know that there are many factors that affect the fading of plastic products. Among them, the pigments of plastic colorants, the light resistance and oxidation resistance of the dyes all have certain relevance. The effect of lightfastness directly affects the degree of fading of the product. This is also the light fastness showing a graded performance. It is worth noting that if light stabilizers such as absorbers are added to the masterbatch, the light resistance of the product can be improved. Heat-resistant pigments discolor and fade at the processing temperature, and the molecular structure of organic compounds changes and decomposes at a certain temperature. Nevertheless, in the injection molding process, certain organic pigments with antioxidant properties undergo macromolecular degradation and fade after oxidation. These are inseparable from high temperature oxidation and strong oxidant oxidation.

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