Effect of lubricants on PTFE/PTFE friction under high pressure.

[RPstress]

I have two surfaces coated with thin PTFE sheet which will be under high pressure (possibly up to 150 ksi/1000 MPa). I wish to minimise friction between them for very small amounts of movement (maybe 0.05"/1 mm) at very low speed (a minute or two for that movement). Getting any sort liquid between the surfaces would be very hard, but what about a dry lubricant? Could there be any benefit?

Any thoughts much appreciated.

 

[rnd2]

Try rubbing molybdenum disulphide powder onto the surface of the PTFE. How thin is the PTFE sheet?

 

[RPstress]

Thanks. The sheet is intended to be very thin. It's part of a test specimen for assessing the effect of through-thickness compressive stress on the interlaminar shear strength of composites, and if the total thickness of both sheets is more than a few thou of an inch we think it may compromise the test results. Ideally, we'd like just one or two thou thick.

 

[Compositepro]

The teflon sheet itself is your lubricant. You do not need anything more. Teflon cold flows under shear stress and that is why it is used as a lubricant.

 

[RPstress]

Any guesstimates as to the amount of friction? We are a bit worried that we could get an effective static coefficient of friction of 0.15 or so. We'd like it best if we could get down to around 0.05 (or less, of course).

If there's genuinely no point in adding anything then in some ways it would be a good thing: due to the nature of the specimen we have to add any lube before curing it (350 deg F), so we can't test with and without easily.

 

[Compositepro]

Teflon at low presure is usually listed as having a coefficient of friction of 0.1. If you are looking for 0.05 you will probably need some rolling bearing or pressurized lubricant feeding a plain bearing.

 

[RPstress]

Due to the nature of the beast it's going to be almost impossible to get any fluid in there; hence my interest in a dry lubricant that we could put in as we made the composite laminate. It'll only be used the once, as the specimen is tested.