roamingnome
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Recasting teflon
I have a large assortment of PTFE stoppers mainly, and Ill use some,
but if they can be ground and recast into a more useful shape like a thick tube or teflon beaker this would be great.
melting of some plastics causes shrinkage
Has anyone melted teflon to fatique?
[Edited on 13-6-2008 by roamingnome]
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Eclectic
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I don't think you can melt PTFE.
Most items are made by press/sinter of the powder.
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kilowatt
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There is a fine line between melting and decomposition (to deadly gases such as HF and fluorophosgene). You must operate on that fine line which is
around 330°C to cast it. Decomposition will already be taking place to some degree at that temperature and I believe you will need a good fume hood
and scrubber system. I have melted very small amounts of PTFE before but have not cast anything. It would require constant heating. In industry it
is injection molded at somewhat below its melting temperature, like pretty much any other thermoplastic. If you can set up presses and molds for
injection molding, that is the best way to do it.
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Panache
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It won't flow even if you can dance on the ever so thin line kilowatt mentioned, so casting is impossible. i understood teflon to have too poor a melt
flow index for injection moulding and that machining or sintering the powder is about it, hence the expense of anything manufactured from teflon,
except teflon tape which is reasonably inexpensive.
Best thing is to drill your stoppers into shavings and using the teflon 'wool' for everything under the sun in your lab.
[Edited on 13-6-2008 by Panache]
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Ozone
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IIRC, PTFE goes "gelatinous" at the "melt" temperature (the "fine-line"). If you had the proper mass to fill a two-part mold, you could heat it until
gelatinous, then press it between both halves of the mold (heated at the same temperature as the melt and then cooled in some controlled way) to cast
the object that you want.
I really like the PTFE "wool" (it does turn very nicely, beautiful in a drill press or end-mill) idea, though, and will definitely keep that in mind.
Cheers,
O3
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--Albert Einstein
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BromicAcid
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http://www.sciencemadness.org/talk/viewthread.php?tid=2090&a...
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roamingnome
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well it seems then, that simply buying 1-2 inch stock is the most direct and safe way of making a microwave cavity.
If scrap PTFE from grindings/millingings/shavings is used, the polymer chain length would then be shorter.
This would effect the polymers property's in some way for sure. Something maybe interesting, but not for moderate pressure conferment.
[Edited on 15-6-2008 by roamingnome]
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MagicJigPipe
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I would like to add that I have tried to melt and "recast" teflon before via conventional heating and determined it to be all but impossible. The
"liquid" point and decomp. point are so close that they seem to happen simultaneously.
It always gets "charred" and really never fully "melts" because of that.
"There must be no barriers to freedom of inquiry ... There is no place for dogma in science. The scientist is free, and must be free to ask any
question, to doubt any assertion, to seek for any evidence, to correct any errors. ... We know that the only way to avoid error is to detect it and
that the only way to detect it is to be free to inquire. And we know that as long as men are free to ask what they must, free to say what they think,
free to think what they will, freedom can never be lost, and science can never regress." -J. Robert Oppenheimer
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chief
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A lot of chemists are said to die of teflon-overheating- accidents; it's said to be very painful too.
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Panache
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| Quote: | Originally posted by chief
A lot of chemists are said to die of teflon-overheating- accidents; it's said to be very painful too. |
What accident ensues when teflon overheats?
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DrP
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| Quote: | Originally posted by chief
A lot of chemists are said to die of teflon-overheating- accidents; it's said to be very painful too. |
I've never heard of chemists dying because of PTFE over heating. Canaries and other birds kept in kitckens have popped off when teflon coated non
stick frying pans are left on. The worst I've heard of is 'polymer flu' where you get flu like symptoms from exposure to the very small amount of
dangerous products given off if the PTFE is burned up.
I'll have to do a search for teflon related deaths when I get the time. Can you reference any links to such a situation?
\"It\'s a man\'s obligation to stick his boneration in a women\'s separation; this sort of penetration will increase the population of the younger
generation\" - Eric Cartman
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roamingnome
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| Quote: |
Canaries and other birds kept in kitckens have popped off when teflon coated non stick frying pans are left on |
I go to this lady at work, hey cool your useing cast iron pans, and she says its for the birds....
after giving here a puzzeled look she explains that yes they die
but teflon flips the eggs good, any toxin cant be good for us in the long run though
anyway...
"Several lines of evidence have suggested that hydrolysis of PFIB and resulting production of hydrofluoric acid may be responsible for pulmonary
damage"
Overheating of PTFE generates fumes of highly toxic PFIB and poses a serious health hazard to the human respiratory tract. PFIB is approximately ten
times as toxic as phosgene [2]. Inhalation of this gas can cause pulmonary edema, which can lead to death. PFIB is included in Schedule 2 of the
Chemical Weapons Convention (CWC),
teflon: a blessing and a curse
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F2Chemist
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Also, heating PTFE generates TFE (a great way btw to get tetrafluoroethylene "IF" you know what you are doing). In high concentrations, TFE when
exposed to oxygen deflagrates creating a LOT of energy as well as CF4, C, and other CFO species. Meaning, if it's in high enough concentration and
is exposed to oxygen (or any other radical for that manner), it will go boom (has about the same power gram for gram as TNT if I remember right).
For this reason TFE is dangerous stuff and I wouldn't recommend ANY amature chemist messing with it. Typically it is stored in a cylinder with ~20-50
wt% CO2.
Most TFE polymerizations are controlled emulsion or solution polymerizations where the TFE is slowly bubbled into the pot, thus there is never a high
concentration...and these reactions are done behind large blast shields.
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