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| Author | Topic: Reversion/Orientation |
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swickham Senior Member Posts: 7 |
posted September 01, 2005 07:12 AM
   
Please could i have feedback on what parameters affect reversion/orientation inthe production of HDPE sheet. IP: Logged |
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Tom C Moderator Posts: 592 |
posted September 01, 2005 09:26 AM
If you want to orient the product, then stretching the melt and freezing it in place is just about the only method. Typically this is associated with oriented film and monofiliment. I you want to reduce stress in the product the influential items are: Rate of cooling the product. I have also seen tests recently where a unique screw design produces a "Low Stress Melt" which seems to strongly influence the flow and handling characteristics of the product. I you would like, email the process details to me and I will run an analysis on Compuplast's sheet die and roll cooling software to see anything shows up. This information will be posted here. Specific geometry is not shown. ------------------
Tom Cunningham
Extrusion Technical Services www.ExtrusionTechnicalServices.com IP: Logged |
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Steve H Moderator Posts: 369 |
posted September 09, 2005 03:57 PM
The size of the rolling bank of melt between the first two chill rollers could be a factor also, you don't want ot have one for HDPE. Running temps on your chill rolls could be a factor, try running higher temps. You could also check the speed differential between your chill rollers and pull rollers, too great difference could be a part of the problem. Tom mentions drawdown, for HDPE your lipset should be 5-10% over the target gauge, and you want as smaller gap between the die lips and the first nip between the chill rollers. ------------------ If at first you don't succeed, skydiving is not for you. IP: Logged |
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