LuckyWinner - 21-6-2021 at 07:15
older threads recommend natural rubber tubing which is not greatly chemically resistant at all...
would thick walled viton tubing be suitable?
what mm outside inner diameter is needed to support almost absolute vacuums?
since its flexible I guess it will collapse if thin walled.
this will be used for solvent distillations...
there are silicone vacuum tubings but they also do not offer good solvent resistance
Chemgineer - 21-6-2021 at 08:51
What about PTFE lined tubes?
Herr Haber - 21-6-2021 at 09:21
PTFE tubing is rigid.
I've never seen lined tubes.
I use Viton for my pump. Just look for something with an absurd inner / outer diameter ratio if you're pulling a really strong vacuum.
LuckyWinner - 21-6-2021 at 11:05
what type of diameter, since my olives have a couple mm I cant go with 2mm inner diameter.
what outer to inner wall do you need for viton to not collapse?
Fyndium - 21-6-2021 at 12:24
It's not too critical in my experience. I have used pneumatic hoses with 8mm ID and ~15mm OD and they never collapse or kink, and I always use 100%
vacuum. For suction filtering I have used ordinary PVC/PU with normal wall thickness and even when they collapse a little sometimes, they work perfect
always. PTFE tubing can be good if it is thick enough, but it is also very rigid, more like tube than hose, and it will kink instead of bend, unless
the radius is huge. I have moved to using discardable tubing which is thick PVC or PU, I use it as long as it lasts and then replace it. Can't really
beat 1€/m price tag.
BromicAcid - 21-6-2021 at 13:30
Usually just have a 50 ft roll of natural rubber tubing, when it gets brittle/discolored change it out. You need to change it out periodically from
accumulated residues.
S.C. Wack - 21-6-2021 at 14:40
Glass. Perhaps the inside of other tube can be coated with something.
The best plan would be traps of perhaps several types in series.
ChemGlass - 21-6-2021 at 16:24
I have a roll of Aldrich Teflon tubing somewhere in storage. I don’t really need it. How many feet of tubing do you need? Are you opposed to having
stiff tubing? I can’t imagine this Teflon tubing collapsing under high vacuum. It’s incredibly strong if I remember correctly from having last
used it. I probably have around 10ft I think. I could spare some if you’d like to see if it works for what you need. Like if you wanted to pay just
for shipping I could send you some Teflon tubing for free. I don’t mind getting rid of a few feet if you’d like to experiment with it.
[Edited on 22-6-2021 by ChemGlass]
macckone - 22-6-2021 at 13:11
4mm OD x 2mm ID teflon tubing is widely available, look under 3D printer parts.
It is very flexible at that diameter. You would need something on either end if it is being connected to a vacuum pump and stand glassware.
If it is just for the area between the takeoff and the pump, just use automotive vacuum tubing.
It doesn't outgas, won't collapse and is resistant to a fair number of solvents, the ones that it won't work with are acetone or MEK. But it isn't
sensitive to non-polar organics. I haven't tried it with amines, and it is not appropriate for nitric acid.
If you use it for nitric acid, you will need to replace it but it is not expensive.
Sulaiman - 22-6-2021 at 15:07
2mm i.d. is rather small for a vacuum line, pumping down may be rather slow.
I would be more concerned with solvent vapours getting to my vacuum pump than interacting with the tubing.
I'd consider long pieces of glass tubing joined by short pieces of tubing.
My dual stage rotary pump does not collapse most thick-walled (2mm or more) tubing (pvc, silicone, rubber etc.)
pvc tubing contains plasticiser(s) that often interact with solvents,
rigid pvc (uPVC) pipe is more chemically resistant.
zed - 23-6-2021 at 22:15
Polyethylene... Kinda Rigid, pretty chemically resistant, very inexpensive. Does not collapse under vacuum.
Long ago, I used to work with the standard vacuum tubing. Very thick walled, very flesible; nice stuff.
I never had a problem with insufficient chemical resistance. It was a pretty expensive specialty item.
Polyethylene, I can buy just a few miles away, at my neighborhood hardware store.
Here is an example utilized in a Nitric Acid distillation by UC235: https://www.youtube.com/watch?v=DEEjNQN2dIQ
[Edited on 24-6-2021 by zed]
[Edited on 24-6-2021 by zed]
macckone - 28-6-2021 at 20:06
No one mentioned kynar (PVDF) tubing.
It is an elastomeric tubing and it is pretty chemical resistant, no ketones allowed though.
It is expensive as hell.
https://www.amazon.com/Kynar-tubing-ID-OD-pack/dp/B003LY99OA
FEP tubing is less flexible but more resistant and comparable to PTFE except for flexibility and melting point.
Obviously additives vary by brand, so some brands may be more resistant than others.
It is not quite as stratospheric in price but still expensive.
https://www.amazon.com/dp/B00T975AZK
The last flexible resistant tubing is FFKM (kalrez).
This is space shuttle type material, and cost. An o-ring can cost hundreds, they make tubing but this is arm, leg, first born and sacrifice a virgin
stuff.
If the solvent resembles gasoline, use automotive gas line.
If it is acetone, plan on replacing tubing.
FEP will work, but is not super flexible and is expensive.
There are various layered tubing types but they are more industrial with the exception of automotive line, which is again not acetone resistant.
As for which solvents, there are charts that will tell you which solvents work with which plastics.
Back to the acetone example, nylon of all things works with acetone, but is attacked by alcohols.