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| Author | Topic: Gel formation |
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Cisco Senior Member Posts: 5 |
posted May 12, 2009 08:49 AM
  
Hello all, I manufacture medical devices using silicone elastomers and I am having a problem with gel formation. Is anyone familiar with cold extrusion? I have been extruding for almost 20 years and have never encountered a gel problem like this. We have tried multiple compounding variations and filtering options, yet the gels continue to form during extrusion. Please help. IP: Logged |
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Tom C Moderator Posts: 930 |
posted May 12, 2009 09:15 AM
Is this a new formulation or process, or is it an established process and the problem is new? Any heating occurring while processing? ------------------ Tom Cunningham www.ExtrusionTechnicalServices.com IP: Logged |
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Cisco Senior Member Posts: 5 |
posted May 12, 2009 10:19 AM
This particular product has been well established, we have been producing it for over six years and have had no issues until late last year. The gels are starting to become a problem in some of our other product lines, all of which we have been producing without incident for many years. We did notice a small buildup of heat during the material compounding step of our process and now have cooling controls to eliminate that buildup. IP: Logged |
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Tom C Moderator Posts: 930 |
posted May 12, 2009 10:40 AM
So the initial impression is that there is a common source of trouble. Any changes with the raw material supply or formulation? Are there any incoming QC tests for gels or susceptibility to geling? Any measure of cure initiation temperature? Any chance of swapping out raw material components with another supplier's to try and identify the source? ------------------ Tom Cunningham www.ExtrusionTechnicalServices.com IP: Logged |
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Cisco Senior Member Posts: 5 |
posted May 21, 2009 01:29 PM
I'm apologize for not replying sooner, I have ben unable to focus on this issue due to other demands. It looks now, thanks to your post and in part a little screw up on our suppliers end, that the material may be a critical factor to the gel formation. I cannot say definitively that this is the root cause of our gel formation at this point, but I believe that it is a large factor in thier formation. I'm thinking that areas in our equipment that contain dead-spots or little areas where eddying of the material is occuring is also a significant factor. Thank you very much for helping me get my head around this problem. IP: Logged |
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Tom C Moderator Posts: 930 |
posted May 21, 2009 02:17 PM
By use of flow modeling software the dead spots and eddy areas can be identified, and new designs tested on the computer for effectiveness. There are newly developed standards for stress between the flow and the metal surfaces, where those surfaces can be determined to be self cleaning or not. By designing the process to be self cleaning, processes like your can show dramatic imrovements in quality. ------------------ Tom Cunningham www.ExtrusionTechnicalServices.com IP: Logged |
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Cisco Senior Member Posts: 5 |
posted May 21, 2009 02:50 PM
Can you recommend any particular flow modeling software? IP: Logged |
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Tom C Moderator Posts: 930 |
posted May 21, 2009 03:36 PM
I just happen to represent Compuplast's extrusion modeling software, and would be happy to present their software to you. Please contact me through the web site; so we can exchange email addresses. ------------------ Tom Cunningham www.ExtrusionTechnicalServices.com IP: Logged |
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