low friction and low temp packing question

I have got to set up with a display engine that will run on low pressure air.

Pressure will be less than 5 psi so I am looking for a packing material that has low friction, but still has reasonably low leakage.
Cheap is good too. :)

Any suggestions?

Thanks,
Bob B.

Delrin (polyacetal) would be my choice for a small air engine. Besides being good for highish temps (>100'C high for plastic) it is springy and allowing for that can be made into its own seal that doesn't need lube. Its very slippery on polished metal.

Something like a cupped piston would work fine as the cupped part could be thin walled and the springyness of the material (maybe compined with the air pressure) would make it a good seal, without the drag of orings or other seals. Its a plastic commonly used in small pump and valve type devices because of those properties.

Quote:

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Originally Posted by RomanLini

Delrin (polyacetal) would be my choice for a small air engine.

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Thank you,

Thanks sounds like exactly what I'm looking for.
I have already located a source and will order some tomorrow.
(Today is a Holiday here.)
Cheers,
Bob B.