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Author
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Topic: TPP extrusion
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shawn8791
Senior Member Posts: 5
From:brazil, IN, USA
Registered: Oct 2006
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posted December 04, 2006 11:42 PM
   
I listed this question a few weeks ago, here is some more information as to what we are trying to achieve.Does anyone know of what extrusion equipment is used to extrude TPP flakes. The material is used as an additive to many plastic compounds, but I havn't found anyone using it alone. Helpful information would be meltflow, extruder L/D, compression ratio for screw, etc. We are wanting to extrude this material into a trapeziod shape, is this achievable? We are also wanting to produce 100 lbs./hr. Hoping to do so on a 2.5" extruder. The material will be extruded as follows: 60%TPP, 35% graphite powder, 5% copper powder. We ran trials on a 30mm single screw and got good results (except we only got 5 lbs/hr @30 RPM). The problem we are facing, is running it on the 2.5" machine and getting 100 lbs/hr. The material doesn't seem to feed very well. If we go above 45 RPM, the melt temperature is uncontrollable, as the melt temperature has to stay between 117F and 119F to extrude a profile. I would assume at the above rates, we would only get around 50 lbs/hr out of the 2.5" machine. Does anyone have any ideas, or a screw design that would help. The 30mm machine was 22:1 L/D, the 2.5 machine is 15:1 L/D. IP: Logged |
2beeps
Moderator Posts: 117
From:Silver City, NM, USA
Registered: Jun 2001
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posted December 05, 2006 10:57 AM
Shawn,
Are your ingredients (hopefully) pre-blended prior to extrusion?? If so, a counter-rotating twin screw (like used for PVC pipe,etc.) will deliver good output rates at lower RPM's than single screws, and at much lower shear rates---so you can acheive higher rates without the higher temps from frictional heats. (Speaking of friction, maybe a very small touch of a lubricant additive like GMS or AC629A PE wax in your blend might allow higher single screw speeds without heat buildup??)Cheers, Skip IP: Logged |
Tom C
Moderator Posts: 801
From:Brodheadsville, PA USA
Registered: Jun 2001
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posted December 05, 2006 02:43 PM
Normally TPP will not have enough melt strength to support a profile. With the fillers perhaps you have a better chance.A viable process might be to compound and pelletize on a corotating twin, and then take those pellets to a single screw for profile extrusion. Special techniques may help with temperature control on the single screw. As mentioned a counter twin may be better than a single for temperature control vs output, however mixing and extrusion in one step with temperature control may be very difficult no matter what the equipment is. I believe I could provide some professional guidance using the extrusion modeling tools and personal experience. Email me if you are interested. ------------------
Best Regards, Tom Cunningham www.ExtrusionTechnicalServices.com IP: Logged |
shawn8791
Senior Member Posts: 5
From:brazil, IN, USA
Registered: Oct 2006
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posted December 06, 2006 11:31 PM
Skip,What percentages for the wax? Who makes it? Tom, What guidance are you refering to? i.e. screw design, consultation, etc.? thanks,
shawn IP: Logged |
2beeps
Moderator Posts: 117
From:Silver City, NM, USA
Registered: Jun 2001
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posted December 07, 2006 11:07 AM
Shawn,A level of 0.1-0.25% of total compound weight should help. Chemtura supplies a variety of lub.additives(GMS? Stearic acid?). AC629A is an oxidized polyethylene wax originally offered by Allied (now a new name----).
Skip IP: Logged |
Tom C
Moderator Posts: 801
From:Brodheadsville, PA USA
Registered: Jun 2001
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posted December 07, 2006 09:39 PM
I am proposing engineering support on how to accomplish your project, which is quite non-standard. I use lab studies of physical properties testing and computer modeling tools as needed to help understand how to handle unusual materials. Specifically I could supply detailed engineering analysis on how to compound the formulation on a twin screw extruder pelletize it, extrude it on a single screw, design a die, shape, support, and cool the product. Resources; Datapoint Labs and other labs for CAE testing.
PolyTech TXS fully intermeshing twin screw simulation software
SPR Extrud 2000 single screw simulation software
Compuplast simulation software for extruder scrws, profile die balancing and profile cooling. First thing to do would be a viscosity analysis of the compound to find out how sensitive viscosity is to temperature and see how feasible extrusion is. I can think of a number of potentials that could help improve your situation.
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Best Regards, Tom Cunningham www.ExtrusionTechnicalServices.com IP: Logged |
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