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Lube for Teflon Washers?

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#26 MattT

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Posted 08 July 2014 - 08:12 AM

Thanks Pete for the info on the cold flow properties. Interesting stuff.

#27 panthers007

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Posted 09 July 2014 - 01:26 AM

Polytetrafluoroethylene = PTFE and it did an excellent job on my Orion AZ-4 mount. And by the by, I happen to be an organic chemist. Consulting these days. Got tired of being a lab-rat.

Woof,

Dave

#28 Lance1234

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Posted 09 July 2014 - 04:30 PM

Soooo...Pete...since you are a chemist for DuPont AND work in the DryFilm department, it seems like you would be in a better position to authoritatively answer the OP's question than anyone else on this forum. Do you lube Teflon washers or not; and if so, what with?

#29 Pete-LH

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Posted 10 July 2014 - 09:07 PM

In general against a flat clean metal surface, a PTFE washer shouldn't need a lubricant to function for the type of movement implied. In fact some lubricants might soften the washer and diminish the performance.

#30 schang

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Posted 10 July 2014 - 09:48 PM

In general against a flat clean metal surface, a PTFE washer shouldn't need a lubricant to function for the type of movement implied. In fact some lubricants might soften the washer and diminish the performance.

The coefficient of friction of PTFE against clean metal is one of the lowest among other materials, including lubricated one. The rationale behind this is beyond me :question:

#31 panthers007

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Posted 11 July 2014 - 01:03 AM

In fact some lubricants might soften the washer and diminish the performance.


Forgive my seeming ignorance here but I have read, over the years, that PTFE is essentially inert regards it's interaction with aliphatic hydrocarbons such as what one encounters with "grease."

I should think that it would be more prone to damage by abrasion, such as would be encountered if pushed up against a rough surface area. Then grease would likely act to protect the PTFE component.

TeflonĀ® Ho!

Dave

#32 Pete-LH

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Posted 11 July 2014 - 03:48 AM

Briefly,

Under the conditons for this use involving light pressure and minimal torque, softening is probably not an issue or at least no more than a surface effect.

PTFE homopolymer is produced by a few different polymerization processes to different molecular weights and particle structures. These are very high molecular weight/high melt viscosity materials, and are processed by techniques other than melt extrusion. The processing techniquestion range from metalurgical processing methods(eg. metal powder processing techniques) to paste extrusion (mixing the powder with a hydorcarbon lubricant, extruding through an oriface to make tubing, wire coating, etc.) to expanded film processing (Gortex®).

There is also post processing of PTFE to make a low molecular weight product termed micropowder which is essentially just a wax (This is the form added to other lubricants to reduce the COF (Coefficient of Friction).

PTFE Co-Polymer (TEFLON® PFA, FEP) are also made which can be melt processed.

There is a lot more detail to this which you can probably find on Wikipedia. These TEFLON® washers are probably made from granular PTFE which is the oldest process (other than that made accidentally by Roy Plunket) involving suspension polymerization to a large stringy particle which is ground to a powder with a particle size of ca 25 microns and then either molded to a sheet or to a billet which is then free form scintered at a temperature of typically 380 deg C. The washers are then cut from the sheet or more likely a billet is skived on a lathe to produce a sheet from which the washers are produced.

The PTFE molecule is very inert but depending on the processing conditions(eg., condition of blade on lathe) there can be micro-porosity where oil (hydrocarbon, silicone, fluorocarbon(Krytox®), or blends thereof including blends with PTFE micropowder) can w penetrate to some degree under pressure which would have a plasticizing effect. PTFE is already soft so any penetration makes it even softer.

Again this might just be a surface effect-most likely minor but suffice to say a lubricant is probably not necessary and I like to refrain from any lubricants/oils when handling optics.

An added note: PTFE(PolyTetrafluoroEthylene) melts 380 deg C but it also goes through a transition between 18 and 45 deg C which involves a slights twisting of the PTFE molecular chains which causes a slight softening effect. PTFE also has a Tg(Glass Transition) at ca 150 deg C where the material transitions from plastic properties to more elastic properties.

"And that's all I'm going to say about that." Check out Wikipedia

#33 Lance1234

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Posted 11 July 2014 - 10:00 AM

I think what Pete is trying to say is that Teflon is made through a variety of magical processes that give us a nice slippery material that works great in various telescope applications...I think. :grin:

#34 Pete-LH

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Posted 11 July 2014 - 12:06 PM

I obviously need to get a life ... Eh?

#35 csrlice12

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Posted 11 July 2014 - 02:15 PM

nah, why clutter up your stargazing time with life nowadays.........

#36 gdd

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Posted 11 July 2014 - 04:53 PM

I think what Pete is trying to say is that Teflon is made through a variety of magical processes that give us a nice slippery material that works great in various telescope applications...I think.



I think he is saying if you add anything to the just about the most slippery material there is you might make it less slippery.

Gale

#37 MattT

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Posted 11 July 2014 - 06:52 PM

Great info Pete, thanks!

#38 Pete-LH

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Posted 11 July 2014 - 08:03 PM

My pleasure MattT. It's what I've done for a living for 30+ years and its probably the only useful information I have to offer to this forum that has done so much for myself.

#39 MattT

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Posted 16 July 2014 - 06:30 PM

Update: I cleaned the washers and the anodized aluminum bearing surfaces on the Dwarfstar with 70% isopropyl alcohol. No apprent solvent-related problems, and the movements are quite a bit better.

Thanks for the advice!

#40 bigdob24

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Posted 31 August 2014 - 07:32 PM

Clean the surfaces well and use white candle  wax. Just rub it on and your good.

i use this on my 24" dobs Teflon surfaces whenever I have it apart.

Easy and no mess



#41 MAURITS

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Posted 01 September 2014 - 01:07 PM

Erdicil, dry silicon spray.








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