Analysis of the causes and preventive measures for black spots appearing on granulated products from plastic machines

When black spots often appear during the plastic granulation process, we need to consider what exactly is causing them. Is it a problem with the granulation machine, a problem with the raw materials, or some other factors? When encountering such issues, our first priority is to analyze the causes.

There are many scenarios that may lead to the appearance of black spots. They could originate from the filler, the raw material, or neither of them, but emerge after carbonization in the screw. An excessive amount of external dust can also contribute to this issue. Additionally, uneven dispersion of carbon powder can cause black spots. Therefore, each specific problem should be analyzed on a case-by-case basis! In the actual production of plastic products, it is common practice to isolate the feed port before shutting down the machine, remove the plastic melt from the extruder and the head, adjust the temperature in each zone, and then turn off the power.

For large and medium-sized extruders capable of plasticizing ultra-high molecular weight plastics, ultra-high molecular weight plastics or their recycled materials can be used with white mineral oil for cleaning. Due to the good rigidity of ultra-high molecular weight plastics, combined with higher temperatures, the cleaning objects will be softened, making them easier to fall off, which is beneficial for the carbides to be carried out by the plastic melt. During the cleaning process, the rotational speed of the extruder is repeatedly switched between low and high speeds multiple times. If there is still margin in the motor load, the extruder can be repeatedly stopped and restarted multiple times during operation to further improve the actual cleaning effect. When the carbides (black spots) in the melt are significantly reduced, switch to the usual plastic cleaning until it is clean, gradually adjust to the appropriate temperature, and then normal production can be resumed.

The harm caused by carbonization to plastic products is not trivial, so it is necessary to avoid its damage to plastic products as much as possible. We should try to minimize the damage. As for the methods, we need everyone to collect and organize information from various aspects. Don't worry about the actual effect, it will definitely have a good actual effect, it's just a matter of time.

Overview:

White pollution is becoming increasingly serious, with waste plastics littering everywhere, which not only wastes resources but also seriously pollutes the environment.

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