Sciencemadness Discussion Board

Sealing Gasgenerators

Organikum - 16-6-2004 at 13:44

One of my bigger problems is solved, the sealing of generators of toxic gasses including the wash and drying-train without the use of expensive wash-bottles with grounded joints or so.

Good experiences were already made by using PLASTILIN, but it was not absolute satisfying regarding adhesion.

The solution now is - mineral pitch aka bitumen aka asphalt.
Available at the next hardware store for sealing roofs.

Have phun, enjoy!

ORG

Tacho - 19-6-2004 at 03:03

Plastilin is a great idea for sealing temporary setups! I never thought of that.

I sugest the use of hot-melt glue. I don't know if this name is used internationally. It is the plastic rod that you melt in a pistol. As you squeeze the trigger it comes out of an orifice as molten plastic.

Its adhesion is much better than plastilin, but not as good as pitch.

Something else: pure pitch behave as a liquid if given enough time. I remember this 50 kg bag that had a hole in it. Looking at the scene you would think it was a bag of black paint that had leaked, making a trail along the shelves and a leaving pool on the floor, but it was all solid.

Organikum - 19-6-2004 at 06:53

Tacho wrote:
Quote:

I sugest the use of hot-melt glue

NO! NO! NO!
Forget it! Dont even think of it!
The chemical resistance of this is zero, nada, nothing, not existing. Perhaps against water for 30 minutes or so.
And NO SILICONE!

Dont make yourself unhappy please. Pitch and Plastilin - they work are cheap and everywhere.
Quote:

Something else: pure pitch behave as a liquid if given enough time. I remember this 50 kg bag that had a hole in it. Looking at the scene you would think it was a bag of black paint that had leaked, making a trail along the shelves and a leaving pool on the floor, but it was all solid

Yes. Same for glass. Give it some hundred or thousand years ..... :D
But in your example its mainly the pressure which causes this effect.

Cyrus - 19-6-2004 at 13:22

I thought tar might be a little hard to clean off of glassware, can I just use alchohols or acetone?

Tacho - 19-6-2004 at 14:05

Quote:

NO! NO! NO!
Forget it! Dont even think of it!


Threw it in the garbage using tweezers! I'll never touch the evil thing again!

Organikum - 20-6-2004 at 06:56

Toluene and xylene remove tar and bitumen quite well. Alcohols dont.

janger - 21-8-2004 at 06:11

I have a few rolls of a type of soft butyl rubber. Ozone resistant. Water resistant. Electrolyte resistant. Fairly heat resistant. Sticks well if need be, else can make temporary seals. Just used it on a chlorate cell with a low positive pressure inside. No chlorine smell at all.
Thanks, say my lungs and throat.

Dave

Saerynide - 21-8-2004 at 07:26

Whats wrong with glue gun or silicone? :o I thought silicone was quite chemical resistant :o

And I agree. Plasticine/Plastilin works wonders :D Its just too oily and slips off everything, but once its taped in place, its not bad :)

blazter - 21-8-2004 at 08:11

There is a plastic material that comes on a roll, and is similar in properties to silly putty, not to mention very very sticky. I really don't know what sort of chemical resistance the stuff has, but its very sticky and makes air tight seals with just about anything. I used to use it at work all the time to make vacuum tight seals with plastic tubing, plastic film to molds, etc, etc. The stuff worked well to temporarly seal up a makeshift aspirator that I cobbled together with some plumbing parts.

Apparently a similar type of material is used to seal beads around windows to window frames, and is known in the fiberglass industry as "monkey glue".

I agree

chloric1 - 21-8-2004 at 12:09

Quote:
Quote:

NO! NO! NO!
Forget it! Dont even think of it!
The chemical resistance of this is zero, nada, nothing, not existing. Perhaps against water for 30 minutes or so.
And NO SILICONE!
I agree I am having problems with my Chlorine genrator becuase I used hotmelt glue. It does not do didly squat!:mad:

JohnWW - 21-8-2004 at 13:41

Whatever it is, it would not stop the very lightest gases like H2 or He from leaking. They can diffuse through almost anything organic.

John W.

janger - 21-8-2004 at 15:41

Quote:
Originally posted by JohnWW
Whatever it is, it would not stop the very lightest gases like H2 or He from leaking. They can diffuse through almost anything organic.

John W.

Hmmm, the butyl stuff I have is similar to what's used to seal electrolytic capacitors. Apparently resists diffusion of gases very well.

Mendeleev - 26-8-2004 at 18:35

This tar interests me because I am planning to generate about 5 mols of Cl2 for a reaction. I am using was bottles consisting of erlenmeyer flasks and corks. I suppose that to seal my apparatus I would simply assemble the flasks/corks and apply the pitch on the outside, or should the cork be dipped into the molten pitch to make it gas proof? Or would you simply take a chunk of pitch and stick it onto the flask?

[Edited on 27-8-2004 by Mendeleev]

Organikum - 26-8-2004 at 22:38

Sealing/impregnating corks the way you described it is the way to go, by dipping them into molten pitch.
You can also make a undersized stopper from plaster of paris and fix this with pitch as a seal - incorporate the tubing and its perfect.
In both cases seal from the outside too use enough pitch/asphalt to keep elasticity on the seals for the tubing.

A pitch-only seal may or maynot work, this depends on your pitch and the diameter of the opening. I prefer and advise to use a solid inlay though.

You should by NO WAY test your setup with a 6 mole load on first run. And you have to test it - first a short, 10minutes test and then consecutive longer ones. Sounds boring. Is less boring than to fuckup a x-mole reaction.
Been there done that :o

Mendeleev - 28-8-2004 at 08:05

I went down to my local hardware store, and I didn't find any pitch, but there were roof sealants with all sorts of elastic polymers, and they were labeled as water proof, I don't know if that's good enough or will chlorine leak through these?

Edit: I went to the hardware store again and found the tar, it's not in the roof section it's in the section with concrete and its used for asphalt not roofs.

[Edited on 28-8-2004 by Mendeleev]

Mendeleev - 31-8-2004 at 17:21

Just to check back in, the pitch is a bad idea. Why? Because it doesn't melt. I heated a 250 mL beacker one third full of pitch on a hot plate on max setting for two hours and it was still solid. When I took matters into the hands of my trusty torch it simply caught on fire. I'm sticking to good old teflon tape and rubber cement.

Hermes_Trismegistus - 31-8-2004 at 18:51

Pitch is not standardized, it can come as goo or as chips, the chips have all the higher fractions evap'ed out.

The goo turns into pitch over time or with application of heat.

it's used up here by the indians, trying to revive the old arts, for making birchbark canoes.

Drop a little random solvent into the pitch to gooey it up a little, it takes time to absorb in though

The indians here use white gasoline,(coleman fuel) in a bucket with the chips for a week or two, they use way too much, then boil off the excess over a fire that was banked to embers, until they reach the proper consistency.

It bursts into flame once in awhile, sorta funny seeing them dance around the flaming bucket of pitch cursing and swearing.

When the heat is applied to the canoe again (in a smokehouse) the solvent fumes away leaving hard pitch. When the seams crack from hard use they either glob on more pitch, or just use a little white gas on the seam and smear it a little and then roast it off with a bic lighter.

It's really funny seeing them slap out the flaming patch of pitch with the palm of their hand and then jump up and down cursing and swearing.

Whatever the "old" ways were, they are slow to be rediscovered.