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Anonymous said:
Then I wonder what happens if one does not adequately dry the raw material resin prior to extrusion? Is it subject to hydrolysis then?
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You may have something there. You obviously know about drying the resin pellets before they get heated up in the extrusion process. If that drying isn't done, then the material starts hydrolyzing with water in the heated extruder.
 






Anonymous said:
You may have something there. You obviously know about drying the resin pellets before they get heated up in the extrusion process. If that drying isn't done, then the material starts hydrolyzing with water in the heated extruder.
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Oops. In the extruder they have a bad combination of elevated temperature and water, leading to hydrolysis even before it gets applied to the lead. Easily solved for the future, but what about all the leads in inventory and patients.
 












Anonymous said:
Can someone explain this in less-technical lingo?
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Absolutely....we have two materials engineers going through the mental masturbation process of trying to figure out how to build a better Optim....a better Optim that will STILL COME APART SINCE THE REAL PROBLEM IS THE SIZE OF THE LUMENS AND OVERALL INTERNAL INTERNAL INTERNAL INTERNAL DESIGN OF THE LEAD.
 






Anonymous said:
Absolutely....we have two materials engineers going through the mental masturbation process of trying to figure out how to build a better Optim....a better Optim that will STILL COME APART SINCE THE REAL PROBLEM IS THE SIZE OF THE LUMENS AND OVERALL INTERNAL INTERNAL INTERNAL INTERNAL DESIGN OF THE LEAD.
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Thanks Genius. The mental masturbation is better than reading your mindless remarks. Why don’t you stop wasting time on a blog, design a lead that sells, and retire?
 






Anonymous said:
Can someone explain this in less-technical lingo?
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Polyurethanes are made of long molecular chains. These chains are composed of different segments. There are "hard" segments and "soft" segments. The hard segments group together and forum semi-crystalline regions within the polymer chain. When you pull on a polyurethane molecular, the soft segments, which are long and spindly, uncoil while the hard segments align in the direction of the pull. The reorientation of the hard segments and semicrystalline nature are what give PU its good mechanical properties.

These soft segments are subject to chemical attack through hydrolysis or oxidation. Basically the break the chains apart and the actual molecules of polyurethane break down and you end up with fractured tubing.

There's moisture in the air. If you don't dry the resin before making the tubing, the moisture in the resin becomes energetic when it goes through the extruder (which is melting the resin to make tubing) and the tubing that you get out has a very low molecular weight and has less resistance to further degradation and will eventually fall apart. The moisture attacks the previously mentioned soft segments.

Various companies make modifications to polyurethane by replacing the chemicals that are normally used for the soft segments with other chemicals that are usually intended to be less subject to the chemical attack. Aortech replaced some of the soft segments with a silicone based material. Presumably you need to dry the resin.


My guess is that the failure mechanism isn't due to moisture from the extrusion but is caused by the catalyst used to make the polymer - probably tin. My guess is that the catalyst itself is attacking the chain and that your silicone soft segments are melting away.
 






Anonymous said:
Polyurethanes are made of long molecular chains. These chains are composed of different segments. There are "hard" segments and "soft" segments. The hard segments group together and forum semi-crystalline regions within the polymer chain. When you pull on a polyurethane molecular, the soft segments, which are long and spindly, uncoil while the hard segments align in the direction of the pull. The reorientation of the hard segments and semicrystalline nature are what give PU its good mechanical properties.

These soft segments are subject to chemical attack through hydrolysis or oxidation. Basically the break the chains apart and the actual molecules of polyurethane break down and you end up with fractured tubing.

There's moisture in the air. If you don't dry the resin before making the tubing, the moisture in the resin becomes energetic when it goes through the extruder (which is melting the resin to make tubing) and the tubing that you get out has a very low molecular weight and has less resistance to further degradation and will eventually fall apart. The moisture attacks the previously mentioned soft segments.

Various companies make modifications to polyurethane by replacing the chemicals that are normally used for the soft segments with other chemicals that are usually intended to be less subject to the chemical attack. Aortech replaced some of the soft segments with a silicone based material. Presumably you need to dry the resin.


My guess is that the failure mechanism isn't due to moisture from the extrusion but is caused by the catalyst used to make the polymer - probably tin. My guess is that the catalyst itself is attacking the chain and that your silicone soft segments are melting away.
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You're hired. When can you start?
 


















Anonymous said:
. . . My guess is that the failure mechanism isn't due to moisture from the extrusion but is caused by the catalyst used to make the polymer - probably tin. My guess is that the catalyst itself is attacking the chain and that your silicone soft segments are melting away.
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I don't think soooo.
Silicone isn't susceptible to hydrolysis
 






Anonymous said:
If it is the accelerated hydrolytic stability test comparing Optim to pelethane it will be meaningless as at the temperatures suggested on this site it is no longer Optim that is being tested as the temperature has broken it down not the hydrolysis. . . .
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What do you mean "it is no longer Optim that is being tested"? It is only Optim in a certain temperature range?
 






Anonymous said:
Absolutely....we have two materials engineers going through the mental masturbation process of trying to figure out how to build a better Optim....a better Optim that will STILL COME APART SINCE THE REAL PROBLEM IS THE SIZE OF THE LUMENS AND OVERALL INTERNAL INTERNAL INTERNAL INTERNAL DESIGN OF THE LEAD.
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What's preventing STJ from getting the right size of the lumens?
 






The lumen size and shape was designed to allow redundant cables. Changing the lumen size/shape is a design change and would most likely result in the need for new testing and a new clinical, especially with STJs track record.
 






Anonymous said:
The lumen size and shape was designed to allow redundant cables. Changing the lumen size/shape is a design change and would most likely result in the need for new testing and a new clinical, especially with STJs track record.
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How about just a little bit smaller lumen so that it hugs both of the redundant cables?
 






who gives a flying f about polyurethane. All this must be very exciting for the egg-heads but where is the linkage to existing product failures? Theres been no talk in any studies of unusual polyurethane behavior leading to lead failures.

Unless anyone has anything to substantiate all this theortetical crap as a cause for existing lead failures, its just a bunch of meaningless blather with no relevance to STJ or the industry.
 






Anonymous said:
who gives a flying f about polyurethane. All this must be very exciting for the egg-heads but where is the linkage to existing product failures? Theres been no talk in any studies of unusual polyurethane behavior leading to lead failures.

Unless anyone has anything to substantiate all this theortetical crap as a cause for existing lead failures, its just a bunch of meaningless blather with no relevance to STJ or the industry.
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You're right. Whoever brought up this alleged Nov 8 release of a December issue containing info on Optim degradation, needs to come to the table and substantiate their claim, or we will call BS on it.
 


















With publications its hard to get exact dates. Sounds like sometime between November and December. The date is leas important than how damaging --or not damaging---the data is
 






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