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 Extrusion, Single Screw
 fish eyes (contanination on PET extrusion)
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| Author | Topic: fish eyes (contanination on PET extrusion) |
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mitch Senior Member Posts: 11 |
posted March 10, 2003 08:47 AM
  
Hello. I am having an issue with a PET resin. We are seeing an increased occurance of fish eyes on balloons we blow from the resin. I have seen some contamination in the resin granuals. Is there any way to elininate this contamination from the resin? Is there any tests i can conduct to confirm there is contamination present? Is there any test i can do to identify what the contamination is? Thank you IP: Logged |
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BrianAndLiz Senior Member Posts: 42 |
posted March 10, 2003 06:38 PM
Could be gels in the resin. Contact your supplier and tell them you are having problems.
Good luck and let us know how you make out. IP: Logged |
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Bob Cunningham Senior Member Posts: 115 |
posted March 11, 2003 06:40 AM
Is this being used in Blown film? One of the tricky things about fighting gels is that it could be too much heat (degradation) or too little heat (incomplete melting). Perhaps a look at a gel under a microscope will give you a clue (if it has a brown center, it could be too much heat). If still no results, you might talk to your resin supplier, since chasing gels can be a complicated issue. Are you using any regrind in your material? -Bob Cunningham IP: Logged |
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louis33 Senior Member Posts: 146 |
posted March 11, 2003 06:24 PM
Paul As a last resort, IF you find that the material is not "clean" you may want to try a candle filter in your process. Blowing ballons is a tricky business when the tube is gel free, with gels, it is imposible. IP: Logged |
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alpertl Senior Member Posts: 49 |
posted March 12, 2003 06:18 PM
quote: Just watch your pressure drop across the filter...... IP: Logged |
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zabielski Senior Member Posts: 386 |
posted March 15, 2003 04:54 PM
Well now, you actually see contaminated resin eh? Get a pair of tweezers, remove some of the contaminaed resin and have an IR done on it. Once identified, you can then try to determine if it's internal or external contamination. If it's internal rooted, seek the path of occurance. If it's external (i.e. came from the resin supplier) file a Corrective Action Notice, as well as a monetary claim for lost downtime, labor, etc. However, if you purchased "wide spec" or "off spec" resin, then you've bought it "as-is" so you'll just have to try a tight screen-pack and catch it all. However, as others have indicated, try slowly to increase mesh sizes, as to high of a screen pack could cause more gels to form. IP: Logged |
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StrapGod Senior Member Posts: 23 |
posted March 15, 2003 09:33 PM
Interesting problem.... but I think you have identified the cause - now for the solution. As from the previous reply, you need to find out where the contamination is comming from. Have you recently changed resin vendors? Is this a new lot of resin? Also, curi9ous as to whom you are buying the resin from? Is it off-spec or prime? Increasing mesh size could very well help also I have heard that mesh type can make a differance in dealing with gels - though I am not aware of which is best. Any more info? Thanks and good luck - let us know! IP: Logged |
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