Why do simulated - leaf flame retardants sometimes have pits and black spots?

Why do simulated - leaf flame retardants sometimes have pits and black spots?

1. When PE is used for flame - retardant injection molding, black spots may appear on the flame - retardant products during the processing. The problem may be caused by the carbonization and oxidation of the flame - retardant materials inside the screw. To solve this problem, attention must be paid to the shutdown maintenance method. It is necessary to use materials without flame - retardant for transition after shutdown for more than half an hour, and start the machine after cleaning the original materials in the screw.
2. Black spots and pits may also appear due to poor dispersibility of the flame - retardant.
3. It may be the problem of the flame - retardant raw materials. There are black spots in the raw materials themselves, and the flame - retardant is incompatible with PE, so it is dispersed onto the surface of the product.