|
Author
|
Topic: Corrugation in foam
|
felix
Senior Member Posts: 43
From:
Registered: Jul 2001
|
posted August 12, 2004 11:23 AM
   
I have come across a scenario where a circular foam die is extrusing foam that is corrugated at densities below 2 g/cc. Above 2 g/cc there is no corrugation present. What could be the cause of this phenomenon? There is a tandem extruder feeding the die. Changes in temp don't seem to affect the situation. IP: Logged |
Tom C
Moderator Posts: 356
From:Brodheadsville, PA USA
Registered: Jun 2001
|
posted August 12, 2004 12:43 PM
Is the corrigation radial or axial?Is the corrigation periodic or random?
Tom C
[This message has been edited by Tom C (edited August 12, 2004).] IP: Logged |
felix
Senior Member Posts: 43
From:
Registered: Jul 2001
|
posted August 12, 2004 04:25 PM
Tom,
The corrigation is axial, that is, in the transverse direction.
The corrigation is periodic. If you didn't know you would think it was done intentionally. IP: Logged |
Tom C
Moderator Posts: 356
From:Brodheadsville, PA USA
Registered: Jun 2001
|
posted August 12, 2004 05:24 PM
Felix,Sounds like a form of shark skin instability which can be wave like. It occurs at the polymer-metal interface when the shear stress exceeds the interfacial strength. A resonant stick-slip effect sets up. It is more typical with high viscosity materials and materials with certain viscosity characteristics. This foam sitiation is diffent. Usually increased foaming agents result in lower viscosity, and the situation should be less likely. Any chance there is some type of screw beat occuring, or inconsistent cooling of the melt across the screw channel? You might look up some the the articles on the www about the "Turbo" screw which is designed to minimize cross channel temperature gradients in cooling extruders. Tom C
IP: Logged |
Contact Us | Feed Screw Designs
Powered by Infopop www.infopop.com © 2000
Ultimate Bulletin Board 5.45a
|
