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purging material

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Topic: purging material

grace
Member

Posts: 1
From:Valenzuela City, Philippines
Registered: Aug 2004

posted August 24, 2004 01:48 AM

Am looking for a purging material for PS foam extruder. A large amount of pelletized regrind are wasted in our process during transition from one colored sheet to another (especially from colored to white. Any recommendations?

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Tom C
Moderator

Posts: 360
From:Brodheadsville, PA USA
Registered: Jun 2001

posted August 24, 2004 09:50 AM

Grace,

Dramatically changing the RPM of the screw while purging has been shown effective. If you have a tandem extruder setup, I'm not sure how safe this might be.

Viscous purges based on cast acrylic are very good at cleaning the screw, but usually the die needs to be taken off, or cleaned if purged through. Again in a tandem setup the cooling extruder might not have enough power to discharge this material.

Some add minerals like talc, calcium carbonate and fiberglass are sometimes added to the purge to increase effectiveness.

In my expereience chemical purges (Rapid Purge) are quick and effective, but somewhat troublesome and messy.

My guess is a combination of chemical purge and rapid RPM changes would be the best for your operation.

Tom C
Extrusion Technical Services

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