Posts: 1
From:algeria
Registered: Jan 2003

posted January 01, 2003 04:33 PM               

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HI,

I need to have detailed explanations of gelation in pvc pressure twinscrew extrusion pipe.

best regards
haf

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Posts: 55
From:McHenry, IL USA
Registered: Nov 2002

posted January 02, 2003 07:23 AM               

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PVC in general, is likely to go into a gel state due to unreacted VC monomer. It is initially caused by poor incoming materials. It is a cross-linking phenomena (gels)that you simply can controll by tight incoming materials specifications. It is further likely to "gel" under heat, pressure, and time (which can happen instantaneously).

Ask your resin supplier for his QA test results and make a CLAIM for wasted production time, materials, and labor. Once your supplier "gets this message", your gelling should become minimal.

Other than this brief explanation, you can learn more about PVC gelling in any PVC hand book.

Keep in mind as well, that other incompatable ingrediants can (and will) contribute to gelling as well. For example, anything with iron oxide will cause fast degredation in PVC.

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Posts: 55
From:McHenry, IL USA
Registered: Nov 2002

posted January 03, 2003 06:58 AM               

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haf:
I've re-read your posted question, and find that I am in error in my response to you.

I have confused "gelation" with "gels". My sincere apologies. Skip's answer to your query on plastic.com EXTRUSION furom is indeed correct, so please excuse my confusion. To many terms of similiar sounds is all that I can offer.

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