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Aqua_Fortis_100%
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High temperature/solvent resistant adhesive (?)
Today I went to hardware stores and found an adhesive called "3M", which says to be resistant against high temperature and pressure ,and advised to seal diesel/gasoline/alcohol engines ..
I'm planning to use this to seal joints between copper pipes and metal lids , to pyrolise some organics like calcium acetate and sodium
terephthalate/NaOH to obtain some volatile chemicals..
I worried about these stuffs and temperatures destroying the seal made with this adhesive..
ps.: the composition of this adhesive on the label is:
acetone, fenolic resin , esterified (? - sorry, I dont know the correct name right now) resin and synthetic rubber..
Can anyone say if this can be useful to these endeavours?
[Edited on 10-1-2008 by Aqua_Fortis_100%]
"The secret of freedom lies in educating people, whereas the secret of tyranny is in keeping them ignorant."
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not_important
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I think that about 200 C is the top temperature for even these types of adhesives. So until the tube is long so the seal is far enough away from heat
to stay within range such products will not work for those applications.
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microcosmicus
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You might want to try some sort of silicone based material
for higher temperatures. Look in the hardware store for the
stuff used to seal joints in stoves.
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Aqua_Fortis_100%
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@ not_important,
Can I try plaster of paris first and then put this adhesive?
I'm worried about the high temps dehydrating the plaster and pulverizing/destroying them and exposing the adhesive..
@ microcosmicus, Early I found a kind of silicone based adhesive, but in the label they say that the max. temp. is 250°C (continuous) and 310°C
(instant) and is not advised against uses where a good solvent appear..
At frogfot's page (acetone synth from calcium acetate), he talks about a special "aluminium paste" used to help in seal the pyrolisis can and able to
resist IIRC 1100°C !!!
Where I can obtain this kind of adhesive?
[Edited on 11-1-2008 by Aqua_Fortis_100%]
"The secret of freedom lies in educating people, whereas the secret of tyranny is in keeping them ignorant."
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LSD25
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Water glass with glycerine and magnesium chloride.
Also consider cutting gaskets from PTFE sheet.
[Edited on 28-1-2008 by LSD25]
Whhhoooppps, that sure didn't work
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not_important
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Plaster of Paris dehydrates on heating. After setting it is essentially gypsum, which loses water at roughly 90 to 150 C to reform plaster, at 189 C
or so form anhydrite - the drying agent form of CaSO4, and above 250 C goes to the "dead burnt" fully anhydrous CaSO4.
Clay has been used to lute joints in heated apparatus, seal crucibles and lids, and so on.
For pyrolysis it might be better to simply try to get a good fitting joint and tolerate a bit of leakage.
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bio2
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This type of epoxy is the highest temperature available.
CASTING, BONDING, POTTING, ENCAPSULATION of electric, structural and industrial components to be used at temperatures up to 300oC (572oF). Casting and
assembly of tools, patterns, models and structural components that must operate in extremely hot and corrosive environments.
Here is one supplier.
http://www.abatron.com/index.html
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MagicJigPipe
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Clay should be restitant to solvents. I mean they might seep through but surely not too much. I know they used to make tobacco pipes out of clay and
that it is fired at around 1000F.
What about some sort of pipe solder?
"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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Aqua_Fortis_100%
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Ok guys, then I will try to diminishe the heating on upper parts of the can and use simply mason cement (1:3 , cement:sand) to seal..
I have to try this soon because I finally found sodium benzoate and have 1kg of it...just happy 
| Quote: | Originally posted by LSD25:
Water glass with glycerine and magnesium chloride.
Also consider cutting gaskets from PTFE sheet.
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Will really this be good? Why glicerine is added? Sodium meta silicate cristals just turned OTC here so can be a good thing to try..
"The secret of freedom lies in educating people, whereas the secret of tyranny is in keeping them ignorant."
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microcosmicus
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SAFETY WARNING !!!
Please, do not use ordinary mason cement for a high heat
application as it is unsafe. At high temperatures, Portland cement can
explode as it dehydrates, sending pieces of shrapnel flying. By Murphy's
law, these projectiles will preferentially aim for your eyes or knock out
some piece of your apparatus and turn your retort into a flaming rocket.
This is why if you look at most any introduction to metalwork, they stress not
to work with hot metal over a concrete floor and why it it standard
practice in workshops and factories which work with molten metal to cover
a concrete floor with a thick layer of sand as a protective measure.
While I have had the good fortune not to witness a major mishap (perhaps
because of the safety warnings) I have had an experience where I was
using a blowtorch, some of the heat fell on a bit of concrete and
ka-pow, a little shard went flying across the room.
Of course, you might avoid the problem by carefully and slowly dehydrating
the concrete first, but then that would give you the same problem as with
the plaster --- it would return to dust.
If you want to use some sort of cement, go to a place that sells fireplaces
or ovens and get a proper refractory cement (or make your own --- ask
if you want more details on how). At least here in the U.S,.
they have a silicate-based fireplace mortar which sticks quite well to
metal and can stand temperatures up to 1100C. For instance, look
at products number 63 and 64 in the following catalogue:
http://dukefire.com/rutland.htm
By the way, product 77 in their catalog is the stove gasket cement I
had in mind in my previous post. (I made a misprint there --- the stuff is
silicate-based, not silicone-based.) It can withstand 1100C and sounds
like just the thing for your application.
Another alternative for sealing is to use some refractory fibers made
from glass, ceramic, or graphite. For instance, see products 90-94
(stove door gasketing) in the above catalog.
If you are not able to locate (or synthesize) a proper material, maybe
do as not_important suggested, but again, pleasestay
away from Portland cement.
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MagicJigPipe
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I can confirm what microcosmicus is saying. I have had concrete explode and send shrapnel everywhere when I was attempting to set something on fire
with a blowtorch. It's bad business.
Also, I was wondering, I know someone that has a fireplace with a "glass" window. I know that it is exposed to direct flame, hot embers and
temperatures well over 800C. Is this quartz?
"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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microcosmicus
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| Quote: |
Also, I was wondering, I know someone that has a fireplace with a "glass" window.
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As it so happens, I have one heating my room right now! My guess was that the pane
was borosilicate, but quartz certainly sounds better. Can you think of a simple
(non- or minimally- destructive!!) test to determine the composition of my windowpane?
While dissolving some of the stuff in HF and then doing tests for Ca, Na, K, BO3---, etc.
(assuming I have or can scrounge up the necessary reagents) would work, I don't
want to take a chip off the window of heater that is keeping me warm and toasty 
[Edited on 30-1-2008 by microcosmicus]
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not_important
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The transmission curves for the UV and IR would tell you, shown neat the bottom of this page :
http://www.rayotek.com/techincal_info_glass_sapphire.htm
And as to the sealing/gasketing question, making a gasket out of a material compatible with the temperatures used may be best. Pottery supply houses
often have loose fiber, 'paper' sheets, and rope, of suitable materials. Note that simple metal to metal seals are used too; these can be similar to
that of the lid of a can of paint, or threaded couplings like pipes use.
[Edited on 30-1-2008 by not_important]
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Jamjar
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An alternative to stove gasket cement is auto muffler/exhaust putty.
http://en.wikipedia.org/wiki/Sodium_silicate
"Sodium silicate is used, along with magnesium silicate, in muffler repair paste. When dissolved in water, both sodium silicate, and magnesium
silicate form a thick paste that is easy to apply. When the exhaust system of an internal combustion engine heats up to its operating temperature, the
heat drives out all of the excess water from the paste. The silicate compounds that are left over have glass-like properties, making a somewhat
permanent, brittle repair."
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garage chemist
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Your fireplace window is most likely glass ceramic, a material that would have lots of potential uses in the lab but can't be worked by glassblowing
techniques.
It can be distinguished from glass and quartz by its tint- compare it to a glass window, you will be able to see a difference if it is glass ceramic.
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microcosmicus
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| Quote: |
The transmission curves for the UV and IR would tell you, shown neat the bottom of this page :
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Unfortunately, I don't have a spectrophotometer, or easy access to one at present
(One of these years I plan to build one inspired by one or more of the
Scientific American plans.) Looking at your chart, however, a
go/no go test with a lamp around 200 nm should work. According to
what is said elsewhere around here, garden variety UV mercury discharge
lamps peak at 254nm, which would put them right at the boundary
of usefulness for the test. So I will pick up a blacklight bulb at the
drugstore in a day or two and get back to you on how the test goes.
| Quote: |
Your fireplace window is most likely glass ceramic, . . .
It can be distinguished from glass and quartz by its tint
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Could you be more specific about this tint --- what color tint does this glass
ceramic you describe have. The thing I have is transparent, appears
colorless (like quartz) , even when viewed on edge through a thickness of
20 mm. Looking at the edges, I see small conchoidal fractures suggesting
that the piece was cut from a bigger sheet with a glass cutter.
In the meanwhile, can anyone think of other quick tests to distinguish
quartz from glass or some other material.
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-jeffB
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| Quote: | Originally posted by microcosmicus
According to what is said elsewhere around here, garden variety UV mercury discharge lamps peak at 254nm, which would put them right at the boundary
of usefulness for the test. So I will pick up a blacklight bulb at the drugstore in a day or two and get back to you on how the test goes.
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Any bulb that you can buy at the drugstore is almost certain to have a conventional glass envelope, blocking any shortwave UV, isn't it?
I think you'd need to find a germicidal or other specialized bulb, and something (a mineral?) that fluoresces differently under shortwave UV
(<300nm) and medium/longwave UV.
I'm facing a variation on this problem: I found a surplus UV transilluminator (UVP TM-36), and I want to verify what wavelength it's producing.
Google suggests that it's 302nm, but some units produce 254nm or 365nm bands as well. It's got a very deep purple filter, so it looked dim when
running, but half the paper in the room (the half with brighteners) was fluorescing brightly. I was trying to come up with materials that would pass
one band and block the others; then I'd use paper or laundered cloth as a wideband detector of sorts.
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microcosmicus
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I looked around more carefully and found it stated that blacklight bulbs block out
the relevant wavelengths for safety reasons. Of course "germicidal bulb" sounds
like something that would belong in a drugstore, but probably not OTC.
Looking further, I found a place called topbulb that sells the right sort of bulb:
http://www.topbulb.com/
In particular, I saw a little bulb for $10.99 that sounds good. It has a screw base and
operates at 10.5V, 3 W, with peak wavelength 254 nm:
http://www.topbulb.com/find/Product_Description.asp_Q_intPro...
I will have to look around more at their site to see what they have, then maybe
order this bulb and perhaps something else.
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LSD25
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Sodium Silicate is used on automobile exhausts, which regularly run around 400+C.
The use of magnesium chloride and glycerine is optional, however this is an extremely thick gel which is useful at lower temps.
If you want a sure bet, use the sodium silicate - just be careful how quickly you ramp up the temperature until you get a feel for the medium (ie. the
size of the reaction vessel, the bore, the heat source, etc.). A couple of dry runs with just the can and the heat source would probably be a good
idea, letting you get a feel for whether you can go full bore or whether the seals will crack if you try it.
For convenience however, a solid copper gasket will probably be the best option (use stainless steel compression fittings and tube). Use the copper
gasket between the top and body of the vessel - remember, if this can be bolted down it will work better.
Whhhoooppps, that sure didn't work
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DrP
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Is there anything that can be added to the sodium silicate to inrease the melting point of its char? For example, adding alumina silicate makes
something similar to a geopolymer and the melting point of its glassy char is increased. I think blending with some K-Silicate can help as well.
Any other ideas appreciated!?!?
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-jeffB
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| Quote: | Originally posted by microcosmicus
I looked around more carefully and found it stated that blacklight bulbs block out
the relevant wavelengths for safety reasons. Of course "germicidal bulb" sounds
like something that would belong in a drugstore, but probably not OTC.
Looking further, I found a place called topbulb that sells the right sort of bulb:
http://www.topbulb.com/
In particular, I saw a little bulb for $10.99 that sounds good. It has a screw base and
operates at 10.5V, 3 W, with peak wavelength 254 nm:
http://www.topbulb.com/find/Product_Description.asp_Q_intPro...
I will have to look around more at their site to see what they have, then maybe
order this bulb and perhaps something else. |
Wow, good find! I was also struck by this one:
http://www.topbulb.com/find/Product_Description.asp?intProdu...
7.2W as opposed to 3W, but 2.2W of UV as opposed to 160mW! (Of course, for your application, less is probably better...  )
For any of these, it would be worth checking whether they require any kind of specialized startup or ballast circuitry.
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not_important
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| Quote: | Originally posted by DrP
Is there anything that can be added to the sodium silicate to inrease the melting point of its char? ... |
Adding alumina, silica, and thus aluminium silicate, and to some extent CaO or MgO, will result in the formation of higher melting glasses if the
temperature is high enough.
If the temperature isn't high enough you can get some reaction where the various solids touch or with melted sodium silicate. This ends up with the
more refractory material forming a mush with molten sodium silicate and glassy reaction products, or a more cemented material if the glass formed
melts higher than the current temperature.
If much glass formation goes on you lose the water solubility of the sodium silicate, meaning you have to hammer and chip the stuff off the apparatus.
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microcosmicus
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| Quote: |
Is there anything that can be added to the sodium silicate to inrease the melting point
of its char?
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I can think of something which could be subtracted --- the sodium. Add some acid
(whatever acid you have on hand --- HCl, CH3COOH, H2SO4 or anything else which
forms a soluble sodium salt will work just fine) to precipitate the silicic acid (slilca
gel). Filter and wash the precipitate. As long as you don't dry it, the gel can be used
in formulating a cement pretty much like the original sodium silicate, but its melting
point is now 1723C. If you don't need that high a melting point, maybe only remove
some of the sodium, for instance only make silicic acid from only some of your
sodium silicate and mix that back into the rest of the sodium silicate and use that.
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microcosmicus
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Looking back at the original post, the problem was to attach a pipe to a metal
lid. A good adhesive for this application is metal --- just braze or weld the
pipe to the lid. Alternatively, as LSD25 pointed out, a good mechanical joint
would also work. For this application,. attach a metal bulkhead fitting to the
end of the pipe --- that is a standard plumbing technique for passing a pipe through
a wall. For as nice description of how this works, see the following webpage which
describes attaching an outlet to a barrel:
http://www.truetex.com/bulkhead.htm
To be sure, the above describes plastic fittings, but the same thing could be done
in metal. If the fittings are well-made and the surfaces mate well --- some filing
and polishing may be required to remove burrs and high spots --- and the fittings
are well-tightened, then the metal-to-metal mechanical joint by itself is going to not
leak even without adding washers or sealants.
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Aqua_Fortis_100%
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Thank you guys, I was very busy and so did not tried my decarboxilation..
So, I will not try with cement, although the temperatures I will use probably will not be very high , because I dont have any kind of blowtorch.. Just
Wood/Charcoal 
I'm probably missing something but I'm just wondering why cement is too bad.. People said bacause of the crystal water, but in Na silicate mix
suggested will also contains water (!?). P. Cement is a material full of silicates (calcium ) and also aluminates (IIRC) + water and it's behaviour
to high heat , as many of you said, is very different of sodium silicate + Mg silicate + water !
My holidays turned dust today
Experiments probably will not be very common in next days
But while this I will buy some kilos of metassilicate crystals and try out latter what you guys advised ..
@microcosmicus, the idea regarding mechanical gasket in joints is also good, although my copper tubes aren't very uniform.. So I would prefer Na/Mg
silicate procedure..
Thanks all!!!
[Edited on 1-2-2008 by Aqua_Fortis_100%]
"The secret of freedom lies in educating people, whereas the secret of tyranny is in keeping them ignorant."
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