I would like to run a reaction that implements both laboratory glassware and stainless steel as well. I don't really want to use PTFE (teflon) tubing
to connect them, I would rather use a fitting that connects stainless to a 24/40 glass inner joint.. Anybody know where to find such a fitting??
Thanks.Magpie - 3-7-2015 at 20:46
Why not use a thermometer adapter.Sulaiman - 3-7-2015 at 20:49
You can also "mold" your own fitting using high temp ceramic epoxy. Many of them tolerate up 4k* f
If you apply a good quality paste wax to the glass fitting, fill the area with the epoxy, once cured the epoxy will release from the glass due to the
wax.
There is also another method using PVA mold release. It is a water soluble plastic that is used in mold making. There are plenty of Youtube vids
showing how it is used.blogfast25 - 4-7-2015 at 06:54
Aaaarrgh! Fahrenheit alert! To the 'decontamination room': 4,000 F = 2,204 Celsius.
byko3y - 4-7-2015 at 07:27
Zom, wtf is "high temp ceramic epoxy"? Did you mean something like epoxy adhersive for ceramics? Most of them can withstand only 150-200°C for a long
period of time, some can handle 250°C. PTFE works fine for the same purpose, while PTFE is leak-tight, can be easily assembled and dissasembled.
If we are talking about a regular ceramic-based adhersive (whcih has nothing to deal with epoxides), than it's basicaly alumosilicate (clay) in its
partialy soluble form. The difference between heat resistant and non-resistant clay lays in the base compound used: whether it is a perfectly heat
resistant up to 1300°C quartz and chamotte, or a regular shitty clay with water in its structure. However, even a regular clay can withstand 500°C
provided it was initially treated at this temperature.
The ceramic is fragile.
You can't use a random one for the steel - you need a special one that have a similar thermal expansion and adhersion to the steel, that's why MgO
containing ceramics are used.
At the same time, graphite-based adhersives have low adhertion to both steel and glass (something like Graphi-Bond 551-RN, which is
graphite+isopropanol+phenolic resin).
For some reason everybody forgot about O-ring and flange joints (which are similar). Anyway, if you need a leak-proof connection between glass and
steel, than you need some kind of gasket between them, because steel and glass can never be fused together - the connection will crack even after
slight change of temperature. And if your working temperature is 300°C+, than pretty much the only gasket you can use is graphite based.Zombie - 4-7-2015 at 12:59
This is what you are looking for. AERMCO makes several epoxies that are either ceramic, aluminium, stainless steel or otherwise reinforced.
I have never adhered it in a high temp situation with glass but I do use it in engine cylinder heads. Expansion / separation has never been an issue.
There are several more brands, and formulas around.
As with all things adhesive... Prep is the key. If you need something to stay stuck, rough up the surface with emory paper. This applies to glass as
well. 80 grit will do.
If you need something to release. polish, and wax the surface.
I don't believe any sort of gasket would be needed if the surface is properly prepared, and the correct adhesive is selected.
We are talking about tiny joins / small surface areas, and manageable temps. Everything will expand together if the right product is used.
[Edited on 7-4-2015 by Zombie]Molecular Manipulations - 4-7-2015 at 13:00
BS byko! Do a little research before pulling nonsense out of you ass...
I've conected SS to glass many times, one must find SS that has similar thermal expansion to the glass you are bonding.
It works because the chromium oxides coating the SS fuse with the sodium silicates and seal perfectly (google glass metal bond). One only needs to
heat the glass to 800 degrees C, as the oxides/silicates defuse without need to be molten.
In my experience this bond is airtight under 400 degrees and even under vacuum.aga - 4-7-2015 at 13:21
If the OP can clarify what the reactants/products are, i might say 'rubber seal' with gusto.localbroadcast - 4-7-2015 at 20:20
Was researching methods for condensing and collecting liquid ammonia.
The glassware would be used for the reaction that produces ammonia as a gas, and the stainless steel portion would be used as a condenser. Stainless
steel has much better properties than glass for heat transfer, and would condense the product much better.
Also, stainless steel tubing is much easier to bend and shape into the desired form for the condenser, and won't have the same issues with cracking
that could happen with glass when exposed to the very cold temperatures of dry ice which would be used to condense the product.
Thanks for the information everyone. Now that I've described the actual usage of the equipment, does anyone still think any sort of adhesive would be
the right thing to use?? lolMolecular Manipulations - 4-7-2015 at 20:35
Almost any OCT rubber gasket will work, don't waste time/fuel fusing glass to SS, just use a gasket.
Really though, any lab glass condenser won't crack at liquid carbon dioxide temp., I'd use that.Zombie - 4-7-2015 at 21:11
Silicone sealant.byko3y - 6-7-2015 at 05:16
Molecular Manipulations, borolilicate glass has thermal expansion (TE) of 3.3*10^(-6) 1/K, no steel has this low TE, pretty much the
only metal having this low TE is some tungsten-molybdenum alloy (don't remember the exact name).
Heating a regular glass to 800 C basically means melting the glass into the metal, and this requires some special equipment and skills.
Also, to make a good seal you need to remove gases from the metal first using a vacuum - otherwise what the point of the connection.
In case of a regular ceramic/alumosilicate adhersive, once again you are forced to use a glass with high TE, which is non-resistant to thermal shock,
and I was sure we were talking about some lab equipment which is supposed to be made from a heat-resistant glass. Zombie, it is either epoxide, or ceramic, not both. That's what I was talking about. localbroadcast, you can use pretty much everything for your task. You can use a glass condenser, though if you stick to a steel
condenser, you can make the connection using rubber or epoxy resin (AFAIK greesing a glass with paraffin will make the epoxy separate, thus letting
you to dissasemble the connection).Morgan - 6-7-2015 at 10:03
Just use a 24/40 glass dewar condenser, that is what most chemists do for ammonia reactions, cool the flask in an ice bath, put a dry ice dewar
condenser on top and that works great. Heat transfer will not matter unless you are scaling up past 1L or more. The book "Acetylenic compounds in
organic chemistry" by Raphael" has an entire section on doing liquid ammonia reactions, complete with photos of the glassware setup. It is somewhere
on the web, I believe. Google books has part of it visible. If you really want to use SS, just use a rubber tubing connector. Trying to connect
anything metal to glass without a rubber bushing or O-ring is an accident waiting to happen IMHO.
Molecular Manipulations, borolilicate glass has thermal expansion (TE) of 3.3*10^(-6) 1/K, no steel has this low TE.
I can't be bothered do the research you should have.
Of course there exists certain SS with similar TE to certain types of borosilicate glass: google is your friend.
BTW, I have no idea what borolilicate glass is.
