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What are the reasons and solutions for black spots on the surface of plastic products?

Views: 364     Author: Site Editor     Publish Time: 2022-12-08      Origin: Site

In the production process, there will always be defective products due to some improper operation methods. In fact, there may not be much difference between defective products and genuine products, such as black spots appearing on the surface of the entire plastic product, such plastic products will be scrapped. So how to avoid such a situation, let's analyze and discuss it below.



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Reasons for black spots on the surface of plastic products

Observe the surface of the plastic product. If the black spot is large, it should belong to the carbonized black masterbatch spot of the raw material; if the black spot is dark, brittle, bulky and porous, it can be considered as a carbonized black spot; if the density of the black spot is particularly large, check that the raw material has no obvious impurities. , Under normal circumstances, it belongs to the phenomenon that the original material is cleaned after the material is changed, otherwise the cause of the material should be investigated.



Solutions for black spots on the surface of plastic masterbatch products

1. Molding impurities may form black spots due to foreign matter mixed into the material. It is necessary to strictly control the cleaning of all links from production, packaging, storage, transportation, reporting, mixing to the barrel.


2. For carbonized black spots, the processing temperature should be strictly controlled, because in actual production, the processing temperature is different from the actual processing temperature. For the same equipment, different back pressures, different cycle times, different one-time injection volumes, and different thermocouple insertion positions will result in different carbonization and degradation trends at the same processing temperature.

That is to say, when the temperature is the same, the back pressure is small, the cycle is short, the one-time injection volume is large, and the thermocouple is inserted in the upper part of the screw barrel, the melt drop/decomposition trend is weak, and it is not easy to produce carbonized black spots. To prevent black spots from carbonization, it is necessary to strictly prevent material accumulation. It is necessary to eliminate the dead corners in the screw barrel, nozzle, and flow channel, so that there is a smooth transition at the turning point, and the area where material may be stagnant is eliminated.


3. The black spots deposited on the threaded surface and the wall of the screw barrel due to the degradation of the auxiliary agent or the existing carbonized material are generally carried out with the production. These black spots will break away from the original attachment surface and enter the screw barrel under various strong shearing effects. discharged in the melt.

This "discharge" process is the process in which black spots and impurities appear in the product. For example, in the production of material conversion and color change, this process of "discharging" impurities is inevitable. In order to shorten this process as much as possible, the method adopted is "cleaning".



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