extreme temperature polymers

[ivymike]

first, a joke:

http://www.shalimarrubber.com/shalimar/physicalindex.htm

VITON RUBBER
Viton is the most significant single elastomer. Its working temperature range is –200 F to +400 F. it has been known to Seal at –650 F in some specific applications.

(Any idea what those "special applications" are? Must be pretty special to operate at -191 Rankine.)
----------------------------------------------
Next, my question: what type of rubber, plastic, or other material can do the following, when applied with a thickness of about 0.2mm:
* adhere permanantly to a metal surface at about 200degC (473K)
* survive exposure to gas in excess of 1000degC
* remain very "squishy" throughout - surviving 10^8 cycles of compression to 50% of its original thickness - surface pressure to compress a rectangular section from 0.2mm to 0.1mm should be in the neigborhood of 2.0MPa (20bar).

 

[MikeHalloran]

Maybe knitted wire mesh.

If it has to also seal, maybe wire mesh impregated with silicone.

What gas?



Mike Halloran
NOT speaking for
DeAngelo Marine Exhaust Inc.
Ft. Lauderdale, FL, USA

 

[unclesyd]

No organic is going to make it, not 1000°C.
A lot of metals get squishy at this temperature and pressure, the only trouble is they don't come back.
To get that number of cycles on anything at any temperature
requires some effort in material selection.

What metal do you intend to use?
What is the gas?

 

[ivymike]

the gas is mostly nitrogen, with some C02, some oxides of nitrogen, and a combination of various hydrocarbons (gaseous and particulate) thrown in for good measure.

I need to use stainless steel or ductile iron (both, in separate instances).

 

[btrueblood]

So, what's wrong with standard exhaust manifold gaskets?

 

[unclesyd]

btrueblood,
I been on and off the air this morning and didn't get to ask the same question?
The solution is an "Old Fashion" gasket made from asbestos with Inconel or SS reinforcement.

 

[ivymike]

so those gaskets can be repeatedly compressed to half of their thickness, and will rebound each time (10 million times)? -I thought they typically only worked once

How would you bond this gasket to the metal surface? (It's not clamped in place)

Aren't those gaskets more like 1.4mm thick, when compressed? The approximate dimensions of this part are to be 4mm by 5mm by 0.2mm.

 

[arto]

these guys have all kinds of good high temp stuff: ceramic glues/threadlockers, etc.:

http://www.cotronics.com/vo/cotr/ca_fastset.htm

 

[GBor]

"(Any idea what those "special applications" are? Must be pretty special to operate at -191 Rankine.)"

I'm guessing space travel? Missions to Mars (successful or otherwise)?

Garland E. Borowski, PE

 

[ivymike]

If the parts were expected to operate 191deg below ABSOLUTE ZERO then I'm guessing the mission failed...

 

[GregLocock]

No, they travelled to the next universe!

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[pennpoint]

ivymike

VITON RUBBER
Viton is the most significant single elastomer. Its working temperature range is –20F to +400F. it has been known to Seal at –650 F in some specific applications.

-20 to +400 degrees F is the normal operating range of this material. I think -650F is a typographical error and should be -65F. With special compounding I suspect its possible but not to -650F.
Still I would not expose it to a temperature of -65F. I do seem to remember somthing about a company named Thiocol and their very critical O-rings failing at low themperature.

ivymike, where did you come up with the -200F figure?

BTW I purposly left off the superscrip degree mark so as not to confuse the syntax. All zeros are zeros.

Regards

pennpoint

 

[ivymike]

Apparently the degree symbol turned to a zero when I copied and pasted. I thought I'd fixed all occurances of that. The -650F read -6500F when I pasted.

I'm not sure you caught the meaning of the joke, though - there is no such temperature as -650F, in this universe anyway.

 

[btrueblood]

Sorry, mike, just trying to be somewhat humorous. Exhaust gaskets (metal-reinforced ceramics or asbestos as unclesyd suggested) work for a single mechanical compression cycle, and tens of thousands of thermal cycles. Usually. If the flange faces are flat and parallel, and stay that way in service.

I don't know of anything to make a seal/gasket at those temperatures and still have a 50% compression resilience for 0.2 mm thickness, and 10^8 cycles. You're looking for unobtainon (the polymer form of unobtanium).

The closest thing that might work (50%, a few hundred thousand cycles) would be an omega-ring (a stainless steel ring with an omega-shaped cross section). The deflection could be tailored to what you want, but the combined thermal/deflection range will limit the fatigue life. Also, it will need to be quite a bit thicker than 0.2 mm to have a 0.1 mm usable deflection range.

 

[GBor]

ivymike,

Did you really expect a bunch of engineers to have a sense of humor? I thought that WAS the joke!

Garland E. Borowski, PE

 

[pennpoint]

ivymike
Ah geez!! The jokes on me!
I'm much too serious, I need a vacation..again.

pennpoint