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| Author | Topic: Un melts |
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miroce Senior Member Posts: 9 |
posted June 28, 2004 05:03 PM
   
Dears Sirs: Actually I am running a formula using (LLDPE+LDPE+HDPE; 1.0, 0.25, 0.05 g/10 min; 30+55+15 %)) for film 2.5 mils, using blown film extrusion line. I have unmelted material (large and small spots) sometimes in line. May somebody tell me the possible causes for above? IP: Logged |
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Tom C Moderator Posts: 344 |
posted June 28, 2004 08:08 PM
What type of screw are you using? What are your processing conditions? Is there wear in the extruder? Are you using filter screens? Generally unmelted resin occurs when the extruder pumps resin faster than it melts the resin. The simple cure is to run slower. Running faster requires engineering and design work. In your case you will also require significant mixing to get all the resins melted, and mixed into a homogeneous melt.
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miroce Senior Member Posts: 9 |
posted June 28, 2004 09:01 PM
Thank you Tom for your reply. What type of screw are you using? Are non barrier screws but I dont know exactly the geometry. The barrells are grooved. Is there wear in the extruder? May be yes, we are awaiting for time to measure it. Are you using filter screens? Yes. 20/80/20 Best regards IP: Logged |
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TomBlack Moderator Posts: 42 |
posted June 28, 2004 10:14 PM
I'm wondering what you're pulling for amps and at what speed are you running. Under these conditions, what is your typical output? IP: Logged |
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Bob Cunningham Senior Member Posts: 86 |
posted June 29, 2004 08:12 AM
I agree w/ Tom C.- that is a very difficult blend to get homogeneous. You have soft, easy melting LDPE combined with stiff, difficult-to-melt HDPE. It may be possible to run those as a blend, but would require a special screw design in my opinion. -Bob Cunningham IP: Logged |
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miroce Senior Member Posts: 9 |
posted June 29, 2004 11:33 AM
Dear Sirs: Thank you for your replies. Actually we have AMPS A B C 55 110 40 producction is around 130 Kg/Hr We have this problem inclusive with formulation using LDPE+LLDPE 35%+65%. Thank you for your interest to help us. IP: Logged |
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Bob Cunningham Senior Member Posts: 86 |
posted June 30, 2004 04:14 PM
Without extruder sizes, max. amp draw, etc., those numbers aren't much help. We'll need pretty much all of the information you can supply in order to be of assistance. One quick thing to look at is your temperature profile. What are your barrel zones set at? -Bob Cunningham IP: Logged |
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Steve H Moderator Posts: 305 |
posted July 01, 2004 02:00 AM
The grooved feed section is driving the problem, as pointed out above without a screw redesign running slower is probably the only thing you can do. Are your screws bored for screw cooling? Steve IP: Logged |
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zabielski Senior Member Posts: 317 |
posted July 01, 2004 05:10 AM
miroce: So that I understand your issue very clearly, your not really running "blends", but seperate layers - correct? You need to do some rheological testing firsthand, as the MI's cited are really meaningless, as it is only ONE value for each resin system. MI is simply an empirical test, and those resins may actually cross each other and give you unexpected unmatched viscositiets. Do a full sweep at three different temperatures, and use all as an overlay to a visual reflection where you can compare each resin to the others. You want ideally, these to intersect as closely as possible. The "N/A" bothers me too. IP: Logged |
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