How to reduce the 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 carbon black spot of the raw material; if the black spot is dark, brittle, and bulky, it can be considered as carbonized black spot; if the black dot density is particularly large, the raw material is inspected without obvious impurities. Under normal circumstances, it belongs to the phenomenon that the original material is clean after the refueling, otherwise the reason for the material should be checked. For the analysis of the above reasons, Jiuzhi Plastics Network recommends:

Forming impurities may form black spots due to foreign matter mixed into the material, and it is necessary to strictly control the cleaning of all aspects of production, packaging, storage, transportation, reporting, and mixing to the barrel.

For carbonized black spots, the processing temperature should be strictly controlled, because in actual production, the processing temperature and the actual processing temperature are different. For the same equipment, it has different back pressure, different cycle time, different one-time injection quantity, different thermocouple insertion position, which will cause 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, and the one-time injection amount is large, when the thermocouple is inserted in the upper portion of the screw barrel, the melt drop/decomposition tendency is weak, and it is difficult to generate carbonized black spots. To prevent carbonization of black spots, it is necessary to prevent accumulation of materials. Eliminate dead angles in the barrels, nozzles, and runners, so that there is a gentle transition in the corners to eliminate areas where material may remain.

Auxiliary degradation deposits or black spots deposited on the threaded surface and the wall of the barrel of the existing carbonized material, generally with production, these black spots will break away from their original attachment surface into the melt under various strong shearing forces in the barrel It was discharged in the middle. This "discharge" process is the process of black spots and impurities in the product. In the process of changing color and color, this process of “discharging” impurities is inevitable. In order to try to shorten this process, the method adopted is “cleaning”.

"Cleaning" method one: cleaning the screw with an empty melt glue.

"Cleaning" method two: the injection of the melting gel, the air-jet rubber, and then the injection of the melt, the air-to-air adhesive, and so on, the practice proves: in the cleaning, back pressure plays a big role, the melt and The screw is strongly sheared. The melt speed is slow, so the glue time is also long. This effect is good, and the foreign matter is cleaned up quickly.