Causes of scorching, corrosion or peeling of the plating layer on the screw when cleaning the screw after XLPE extrusion

There are many reasons why the surface of the screw is scorched, corroded or the plating layer peeled off. It is common in the production of extruded PVC plastics. For example, the temperature is out of control, or the pressure is too large or the electric heating is uneven, or the temperature is set incorrectly. Excessive heating will make the PVC plastic Scorched and cracked, producing corrosive gas to corrode the surface of the screw.
However, in the field of wire and cable coating extrusion, the most common occurrence is that the plating layer on the surface of the XLPE extrusion screw peels off, or the plastic corrodes and stick on the surface of the screw. In theory, XLPE extrusion should not cause serious corrosion of the screw. Many manufacturers have similar problems, but do not know the real reason?

The temperature setting of XLPE plastic for extrusion is generally higher than 200 degrees. XLPE is very viscous. After the extrusion is completed, it is often to use PVC plastic to clean the XLPE residue on the screw. At this time, the ambient temperature in the barrel is still higher than 185 degrees. At this time, when the PVC plastic is used to clean the screw, problems often occur. Because PVC plastic are easily cracked and scorched under high temperature in an environment higher than 185 degrees, generated the hydrochloric acid gas and corrode the surface of the screw and inner hole of the barrel.

Many engineers found that the surface of the screw was corroded, but they did not expect it to happen during cleaning. When the PVC is scorched, if it is a chrome-plated screw, the corrosion of the coating will occur first, then the surface of the screw will be corroded. The lighter is the surface corrosion, and if it is more serious, the surface will be bitten into a pit, and then it will easily cause plastic stick on the screw. If the surface is not seriously corroded, but only rusted, it is recommended to use a non-woven grinding wheel for polishing. First, use #150 to remove the surface residue, and then use a #250 or finer non-woven grinding wheel for fine polishing, and the surface of the screw will be very bright. And finally apply anti-rust oil to avoid rusting again