UnintentionalChaos
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PTFE joint sleeves
So, I have the option of purchasing some VWR teflon joint sleeves (http://www.vwrsp.com/catalog/product/index.cgi?catalog_numbe...) for my ground glass distillation setup, although the cost is around $4.50/ea. For
those who have used them before, are they worth this much and how many uses can I expect to get out of them? Is there an average lifetime, or will
they last more or less forever if I take care of them? Thanks for the help.
I also see that this site: http://www.sciencegear.com/prices-labware.htm#sleeves has them for a lot less ($1.50/ea). Ignoring the $50 min. order, do you suspect that those
are lower quality or is it simply offbrand that makes them so cheap?
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'In organic synthesis, we call decomposition products "crap", however this is not a IUPAC approved nomenclature.' -Nicodem
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DJF90
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The second lot are disposable ones, they are much thinner. The product just below ($10+ each) are reusable.
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entropy51
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Unintentional Chaos,
I know it goes against the conventional wisdom here abouts, but I've tried the PTFE sleeves many times and I keep returning to silicone vacuum grease.
I don't think the sleeves seal that well for water aspirator vacuum, although they do better with mechanical pump vacuum. I don't trust them at all
to seal tightly when distilling bromine or ether.
My experience with standard taper joints is:
1. You don't need grease or sleeves unless the joint will be exposed to vacuum, strong alkali, or temperatures above 100 C. Concentrated inorganic
salt solutions also probably need grease on the joints if the material enters the joint. I use grease for particularly nasty or flammable materials
like bromine and ether.
2. Use a thin layer of grease. I use a robust toothpick to spread a thin layer uniformly around the male joint.
3. Disassemble the joints soon after finishing the experiment, or at least give the joint a turn after it cools.
4. A thin layer of grease can be removed with a paper towel, or if you use too much, immersion in a base bath of 10% KOH in ethanol over night.
I haven't had a joint freeze on me in a very long time, and I've never had one freeze so badly that a quick pass with a heat gun (kept in constant
motion around the joint) wouldn't free it up.
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UnintentionalChaos
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Hrm. How about Glindemann sealing rings? They are rather pricey and don't seem terribly reusable though, but they claim they get a much better seal
than sleeves.
Department of Redundancy Department - Now with paperwork!
'In organic synthesis, we call decomposition products "crap", however this is not a IUPAC approved nomenclature.' -Nicodem
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BromicAcid
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You can reuse Glindemann rings. You get a bunch of them for one price. To get the best seals you have to use two of them.
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Crucible
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teflon tape
How about wrapping joints in teflon tape? Will the hardware store variety work? I've heard if you do it wrong it can put stress on the joint and
maybe crack it. What is the proper way to wrap teflon tape around a joint?
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Panache
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Quote: Originally posted by Crucible  | | How about wrapping joints in teflon tape? Will the hardware store variety work? I've heard if you do it wrong it can put stress on the joint and
maybe crack it. What is the proper way to wrap teflon tape around a joint? |
Go to a plumbing specialist supplier and get them to order in 1" wide gas sealing teflon tape. This is high density TFPE, by standard, not the low
density PTFE used for water pipe. The extra width means you need few overlaps and hence this lessens the stress issues inherent with using tape. I
have not assessed this conclusion just supposed it.
Once practised you require no overlaps and the seal is tres super fantastic. I assessed the leakage rate on my dessicator and i have held a solid
vacuum for weeks using the tape. Silicon grease works better at STP but not for heat cycling conditions IMO. Buy some cheap hairdressing scissors (i
got mine free with an electric beard trimmer), they cut the tape straight and clean.
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Crucible
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| Quote: Originally posted by Panache |
Go to a plumbing specialist supplier and get them to order in 1" wide gas sealing teflon tape. This is high density TFPE, by standard, not the low
density PTFE used for water pipe. The extra width means you need few overlaps and hence this lessens the stress issues inherent with using tape. I
have not assessed this conclusion just supposed it.
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Wow, finding that tape was a quest. They don't carry the yellow gas tape in 1" widths in this area is what I've found. I got the Blue Monster tape
instead. It is supposed to be almost as dense as the gas tape. Hopefully it will do the trick. And I don't know who you are getting to make small
quantity special orders, but none of the plumbing supply shops I talked to were willing to do it without a huge surcharge.
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jimwig
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ebay ebay ebay
http://www.rmiorder.com/index.php?link=browse&code=Z-TT-...
ebay got me there
[Edited on 17-6-2009 by jimwig]
craZy jiM wGGns
--packrat, professional bum. -- once just tired
now REtired.
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Crucible
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Hmmm, they have some interesting stuff on there, but what they don't have is yellow gas sealing teflon tape. They have the regular white tape and the
green oxygen tape. Teflon tape comes in many colors, which correspond to various densities (and probably other things as well).
Ebay does have an amazing variety of teflon tape. For some reason ebay isn't the first place I think to look for hardware store type things like
tape, but there it is. I didn't see any yellow gas tape in 1" width, but that could well change. At any rate I think the blue tape will do. Now I
just need to figure out how to wrap it completely, yet without overlaps as Panache suggested.
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itchyfruit
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saw these on Ebay uk item no :- 110394981487
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chemrox
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try Scientific Machine and Supply in Middlesex, NJ. Ask for Elizabeth or write to info@scimac.com. They developed the process for making these
sleeves and sell them to the other vendors discussed above. They can help replace stopcocks as well.
"When you let the dumbasses vote you end up with populism followed by autocracy and getting back is a bitch." Plato (sort of)
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