posted January 31, 2005 04:27 AM               

In our company we use hot runner molds for PVC injection molding, now we face embedded (burnt particles) or PM problem. Can you suggest some 'good material' to purge my mold and barrel to eliminate this PM problem. FYI, we have tried enough in manupulating temperatures.

posted January 31, 2005 08:43 AM               

If the burning and degradation are occuring while the machine is operating, this is a whole different kind of problem. The solution requires redesign of the runner system to eliminate dead spots.

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Best Regards,

Tom Cunningham

Extrusion Technical Services

posted February 03, 2005 05:57 AM               

Tom C. is absolutely correct. Re-stabilization with a heafty stabilizer package MIGHT save your system.

In reality, take your PVC formulation (pellets or powder) and do a DSC-OIT test to assess how many minutes you have to full degredation. Then take your finished part and do the same.

You'll find that you've probably consumed all of your stabilizer (or nearly all).

Now you'll need to add more stabilizer to satisfy your requirements (BEST BET IS A MASTER-BATCH).

PVC is heat accumlative towards degradation. In other words, it just gets worse and worse - no matter how wonderful you stabilize it.

Consider conventional molding without a hot runner system.

posted July 13, 2005 11:33 PM               

I have found an excellent purge compound for PVC. We used hot tips in our Injection Mold and similar problems with black specs. I found a ready, safe to use Purge Compound called Ultra Purge. It worked great. The Ultra Purge pulled out so much black specs I couldn't believe it. Now I use on a regular basis to prevent the heavy build up. You can find out more about Ultra Purge at www.ultra-purge.com

Let me know how the Ultra Purge works for you.