What are the reasons for the frequent occurrence of black spots in recycled materials such as PP and PE?

In PP and PE recycled materials, manufacturers will encounter many problems that are difficult to solve. Let us give an example today. As we all know, some of the recycled materials are imported from abroad, such as Japan, the United States, and South Korea. There is a PP, PE film, the light is difficult to identify with the naked eye, this film is better in transparency and smoothness, but when you get on the train to the extruder, a small amount of black spots will appear after the process, and the temperature control is appropriate in this process. And no other impurities are incorporated, so why are there such black spots? The reason is that the film is coated with an anti-UV coating at the time of production because of the packaging requirements. The temperature of the coating decomposes at about 120 degrees, and the coating is coked and grayed at 150-160 degrees after the film is plasticized. It is the black dot that appears above. This leads to a reduction in the price of the film and a loss of production. Therefore, some manufacturers must pay attention to this PP, PE film when purchasing, so as not to bring unnecessary losses.

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