Elastomer for extreme high temperatures

[Speedy]

I require an elastomer that will survive at least a couple of hundred cycles in a high pressure combustion chamber. Peak temperatures of 2,000 C or more.

It's application is to protect metal parts that bounce around when the o2/ch4 mixture is ignited.

Am I asking too much?

I have requested info on Kalrez from DuPont.
If there is any other material that would do, I sure would like to hear about it.

Cheers!
Speedy

 

[mcgyvr]

Did you mean to write 200 deg C.?
Kalrez is only rated to 327deg C service temp. 2000 is FAR off.

 

[EdStainless]

You will need to use metallic o-rings. They are usually 'C' shaped and some have a coil spring inside to help, but at high temp the spring is worthless.


= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[unclesyd]

Can you comeback with a little more information about you application?

Are you talking about a chamber were you will be igniting O2/CH4 and you want to protect the individual components?


There is no elastomer, organic, and very few metals that can survive under your stated conditions.

 

[Speedy]

Actually peak temperature range from 2500 to 3300 Deg Celcius. Remember this is the peak temperature of the combusting gas.
The chamber is externally water cooled and maintained below 100C.
We use ordinary mild steel for trial tooling and stainless for production.

I know it is a long shot but I would like to try an elastomer in there, even for one or two cycles

 

[israelkk]

Rubber is used in rocket motors for sealing and an insulation of the motor case from the hot gases. However, it is used only once. The rubber doesn't melt but sublimate therefore, it it is thick enough it may hold few times. I suggest you check NASA documents server.

 

[unclesyd]

We used equipment by Surftran, now Extrude Hone, to deburr precision metal parts. This process is very similar to your proposal.

There were sevral tests to remove flashing from polymer parts with this equipment and all were complete failures.

http://www.extrudehone.com/tem.html

http://www.extrudehone.com/media/index.php?cat=tem

 

[btrueblood]

I've used silicone rubbers and RTV compounds, as well as Viton or similar fluroelastomers, for sealing in various test combustors for limited times, similar to what israelkk describes. It was a "material of choice" for mounting/sealing windows in test combustors, since the silicones generally have very good combined high-temp. capability and mechanical damping properties, helping to reduce mechanical shocks from the ignition transients. Any old ordinary off-the shelf RTV will work okay for this.

Generally, the tech's. prefer silicone rubber seals, as they tend to degrade without getting gooey, and cleaning out the seal groove is simpler. The final answer may depend on what form you need the rubber in (sheet, coating, gasket, O-ring) vs. cost vs. ease of installation/removal/re-installation.

Somewhat funny story an old aero structures prof. related to me: apparently the Space Shuttle tiles use a silicone compound to adhere them to underlying structure. Concerns over launching in cold temperatures (water penetrating the porous tiles and freezing, causing them to crack) prompted the manager types to request the tiles be coated with a waterproofing compound. A product very similar to Scotch Guard was used...which contains silicone oils...which dissolve silicone rubber adhesives. He received a panicky call one morning requesting his presence at a high-level meeting to figure out why all the tiles were falling off of an orbiter being prepped for launch; they pretty quickly figured out why. I told you that story as a way to hint at methods to remove old silicone rubber RTV. The old ScotchGuard formulation is no longer readily available, but silicone oils in varying viscosities is.

As far as ablative thermal protection (doesn't sound like that's what you are after), there are some specialty ablative compounds available out there, that char/ablate below specific temperatures, protecting such things as acoustic test bombs, pressure probes, thermocouples, etc. for short durations during rocket ignition tests. NASA would be a good place to start. Typically, the formula includes some type of epoxy or similar resin binder, combined with fillers or foamed to reduce the thermal conductivity through the material. You might also be able to find them googling around (I couldn't), or researching articles in the AIAA Journals that discuss any of the buzzword terms I've tossed out above...but you will tread thru touchy ground as the products are likely to be export controlled for the USA.

 

[btrueblood]

sheesh. Soon as I wrote and sent the last paragraph above, I looked down the search page and saw

http://www.flamemaster.com/Products&Services/

look under coatings.


For even more fun, see

http://www.wipo.int/pctdb/en/wo.jsp?WO=1995/16751&IA=WO1995/16751&DISPLAY=DESC

 

[MintJulep]

You really haven't explained exactly what your requirements are yet.

Your first post mentions "couple of hundred cycles" and "temperatures of 2000 C or more".

Then in your second post "2500 to 3300 Deg Celcius" and " maintained below 100C". And you have decreased the cycle requirement by two orders of magnitude. "even for one or two cycles". And you throw in a tid-bit about stainless and mild steel tooling.

It's hard to get good advice when you can't communicate what you need.

 

[Speedy]

Sorry Guys - let me be a little clearer.

The ignition temperature of the gas is between 2500C and 3300C, as the ratio of fuel mixture and charge pressure can be varied.
The 100C maximium - this refers to the external temperature of the chamber which is water cooled.

As for cycle life - we can live with a few hundred cycles. We can simply replace the rubber on a daily basis.

To initially test the idea any rubber that would survive even one or two cycles would have been just to initial test the concept.

In a nutshell - an elastomer for maximum temperaure and max life.

 

[Speedy]

Sorry let me add also -
The application is simply to place internally on the bottom of the chamber under the tooling to dampen any vibrations from the combustion. I believe any elastomer will help greatly, it doesn't have to be high in inherent damping.

 

[btrueblood]

Go buy a "Sil-Pad" cookie sheet at your local cooking supply store. This is a fiberglass (or nomex?) reinforced silicone sheet.