RogueRose
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Has anyone used plumbers TFE paste / joint compound for glass joints?
I was at the hardware store and they had a few different products, one was a "90% silicone grease" and the other was a TFE paste/joint compound. I
think the price was cheaper for the TFE, maybe 1/2 or 1/4 the price, so I held off on getting any. The stuff does contain PTFE
https://www.amazon.com/Harvey-023045-Pint-Paste-Teflon/dp/B00004SWKE
I think the temp rating for the product at the store was 400F, which seems pretty high, and says it liquifies at 500F (would be nice to find out exact
#) IDK if silicone grease is higher.
The label from the link does say that it doesn't harden, so that seems like a good thing especially if it is $10 for 8oz of product.
This looks to be the same thing, but smaller size and available at Ace
https://www.acehardware.com/departments/plumbing/solvents-and-cements/plumbers-putty-and-sealers/4396321
Upon looking at the silicone grease, it's rated at 400F as well.
Has anyone tried this PTFE based compound? I'll probably buy some and test it out unless someone has already tried it and it didn't work, I don't
want to ruin glassware.
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Sulaiman
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I just want to mention that I've mostly changed from silicone grease for sealing ground joint glassware - to plumbers ptfe tape,
a single-width winding of a few turns on the male part;
. works really well to seal,
. does not form tar when exposed to halogens as silicone grease does,
. is easy to clean up compared to grease,
. does not dribble grease into the reaction vessel when hot,
. makes Keck clips a little tighter,
. allows a tiny bit of 'wiggle' - useful for larger glassware setups where a spherical joint would normally be used.
So far I've not found a reason to use silicone grease for glassware since using ptfe tape.
CAUTION : Hobby Chemist, not Professional or even Amateur
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UC235
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Quote: Originally posted by Sulaiman  | I just want to mention that I've mostly changed from silicone grease for sealing ground joint glassware - to plumbers ptfe tape,
a single-width winding of a few turns on the male part;
. works really well to seal,
. does not form tar when exposed to halogens as silicone grease does,
. is easy to clean up compared to grease,
. does not dribble grease into the reaction vessel when hot,
. makes Keck clips a little tighter,
. allows a tiny bit of 'wiggle' - useful for larger glassware setups where a spherical joint would normally be used.
So far I've not found a reason to use silicone grease for glassware since using ptfe tape.
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Yeah, but it has to be a single layer only, evenly wrapped, and not forced too hard into the other joint if heating. I broke several rbfs while using
multi-layer tape, and heating before I figured it out. Coefficient of thermal expansion is much higher than glass.
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Sulaiman
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I'll keep that in mind ... thanks
CAUTION : Hobby Chemist, not Professional or even Amateur
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Arthur Dent
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I use silicon dielectric compound, similar to this: https://www.walmart.com/ip/Versachem-15339-Dielectric-Connec... (mine is from Canadian Tire, at $13 or $14 a tube...)
It's chemically inert (even with Nitric acid) , has a nice, tacky, even surface contact, resists pretty impressive temperatures. So far, no
complaints, I also have authentic Beckmans glassware joint grease, and I see no difference between the two.
--- Art is making something out of nothing and selling it. - Frank Zappa ---
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hissingnoise
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IMO, the one thing better than PTFE tape would be Glindemann Rings, also PTFE ─ has anyone here been able to get their hands on them?
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wg48temp9
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| Quote: Originally posted by hissingnoise | IMO, the one thing better than PTFE tape would be Glindemann Rings, also PTFE ─ has anyone here been able to get their hands on them?
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I did not know what the details of Glindermann rings. But I found this web site see: http://www.glindemann.net. It says a groove is required in male part of the joint to hold the ring. Interestingly the groove looks smooth/polished
not the frosted look of the lapped part of the joint and similar to the smooth/polished barrel of a PTFE stopcock.
The site claims its a high vacuum seal which is surprising to me if its sealing against a lapped surface and not a smooth one. Perhaps having such a
small contact area relative to a sleeve, it has sufficient contact pressure to seal against the rough surface of barrel.
Although you have to buy a minimum of 200 the price per ring is less than 50p. That is much better than the typical cost of a sleeve at £10. But
given a ring needs a groove, PTFE tape is the DIY solution. I doubt that the difference in thermal expansion between PTFE tape and borosilicate is a
problem given how soft PTFE tape is.
I am wg48 but not on my usual pc hence the temp handle.
Thank goodness for Fleming and the fungi.
Old codger' lives matters, wear a mask and help save them.
Be aware of demagoguery, keep your frontal lobes fully engaged.
I don't know who invented mRNA vaccines but they should get a fancy medal and I hope they made a shed load of money from it.
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RogueRose
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| Quote: Originally posted by hissingnoise | IMO, the one thing better than PTFE tape would be Glindemann Rings, also PTFE ─ has anyone here been able to get their hands on them?
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I have something similar to these rings but it is an entire sleeve, but I only have one and it does work really well. I found some online for about
$45 for 6 and some places were charging about $30 a piece. The sleeve is the length of the joint. If anyone lives in France, there is a chemistry
supply company that sells these for a good price, about $15-20 for 6, but their international shipping was like $30 I think.
If anyone is interested, I can try to find the link to the site.
To everyone who replied, thanks for the info, I think I'll try the tape and see how it works.
On another note, I found on a few college chemistry guides and they recommend glycerin for things that don't involve reflux and aren't very high temp
distillation.
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hissingnoise
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| Quote: | | I did not know what the details of Glindermann rings. But I found this web site see: http://www.glindemann.net. It says a groove is required in male part of the joint to hold the ring. |
I hadn't heard of the groove before, so I assume it's not strictly necessary ─ earlier ads made no mention of them and suggested instead the use of
2 rings for vacuum work...
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XeonTheMGPony
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Ooooh I have a Crappy tire near where I work, will check out, for me it will be perfect as I need Dielectric grease for my electrical stuff too!
thanks.
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Abromination
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I use petrolium jelly to seal the joints when I use vacuum filtrations although it is not very chemically inert and melts if you heat it.
List of materials made by ScienceMadness.org users:
https://docs.google.com/spreadsheets/d/1nmJ8uq-h4IkXPxD5svnT...
--------------------------------
Elements Collected: H, Li, B, C, N, O, Mg, Al, Si, P, S, Fe, Ni, Cu, Zn, Ag, I, Au, Pb, Bi, Am
Last Acquired: B
Next: Na
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Herr Haber
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| Quote: Originally posted by RogueRose |
I have something similar to these rings but it is an entire sleeve, but I only have one and it does work really well. I found some online for about
$45 for 6 and some places were charging about $30 a piece. The sleeve is the length of the joint. If anyone lives in France, there is a chemistry
supply company that sells these for a good price, about $15-20 for 6, but their international shipping was like $30 I think.
If anyone is interested, I can try to find the link to the site.
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It looks like everyone is carrying these in France.
It's even in the "public purchase" catalogue if you are an administration.
30 bucks is theft though (havent seen it). It should be the price for 10.
I think Scientific Equipment of Houston carries them in the US.
They also have fantastic PTFE keck clips. The last clips you'll ever need.
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