posted November 13, 2006 12:09 PM               

We have extruded FKM but unfortunately we face some pickles in the surface of the extruded rubber. now we need to get rid of the defect. we are using a 50 mm extruder and the pressure we see is very high ( 600 bar)

can you tell me some suggestions to get rid of the defects.

posted November 13, 2006 01:27 PM               

Very high viscosity materials typically have problems with overheating. Can you check the melt temperature? Is it within an acceptable range?

Also high viscosity resins can sometime pump very efficiently in the screw, but the melting rate does not keep up. Is it possible the defects are unmelted resin?

If the melt is too hot, you will need a deeper screw that can be run at lower RPMs. Watch out for drive power limitations.

If melting is the problem, try raising the temperature. If that does not help you will need a shallower screw. or unmelt barrier, to help with the completion of melting.

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Best Regards,

Tom Cunningham