Causes of Carbon Contamination in Sheet Extrusion

The best way to find and remove carbon contamination is to find the root cause.

Normally, some of the causes could be the following:

1. You have issues with the heaters in the barrel of the extruder

2. You missed something with the resistance controls

3. You left resin in the barrel for a long time unattended

4. The temperatures are incorrect for that setup

5. If the contamination is at the beginning of the shift, it is most likely that residues of material from the previous day remained in the extruder and it degraded to the point of charring.

The solution for item 4 is to purge the extruder and die with a commercial purge that has glass fibers such as Asaclean EX. Obviously, you have to follow the purging instructions to have the highest efficiency. Once clean, continue with normal production, checking the product for contamination by black spots.

The most optimal way to avoid or eliminate carbon contamination is to frequently use a non-glass-filled Asaclean grade that allows for extruder sealing and die-off at machine shutdown. This type of grade will allow you to shut down, seal and start the extruder and die without any problem thus avoiding downtime and scrap. It is recommended that the correct procedures be followed to reduce the possibility of misuse of the purge.
In conclusion, use the EX grade to directly remove carbon when the machine is already contaminated. But prevention is always better and for that, it is best to shut down and seal using an Asaclean non-filled purge.

Ready to reduce your production downtime to protect your profits? Learn more about how purging compounds and process efficiency work in tandem.