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Topic: Can a synthetic oil behave as a dry lubricant?  (Read 1712 times)

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Offline xchcui

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Can a synthetic oil behave as a dry lubricant?
« on: August 17, 2023, 06:38:44 AM »
Hi.

I have a lubricant that it was made special for cylinder locks
as it doesn't leave a sticky residues inside the cylinder.
You spray it through the part where the key is inserted to lubricate the
pins/springs/bores.
At first i thought that it was made with solvent and ptfe as it clean
and leave a dry ptfe lubricant.But later i checked the MSDS.
Where it says that it contains:
A  preparation  based  on  synthetic creep oil
and  synthetic  isoparaffins.(cas. number:68551-17-7).
The mix of isoparaffins(C10-13)are the solvent that use as a cleaner
and the synthetic creep oil is obviously for lubricate the cylinder.
After i use the product the cylinder was cleaned and lubricated indeed.
At first the key has a light oil on it when i insert the key,but after a 1 day the
key looks dry,like it is a dry lubricant.It does it job,but i wonder how a synthetic oil can behave like a dry lubricant?it is not dry silicone,it is not ptfe or graphite,it is synthetic oil.
How a synthetic oil can behave like dry lubricant?

Thanks.




Offline Enthalpy

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Re: Can a synthetic oil behave as a dry lubricant?
« Reply #1 on: August 17, 2023, 02:22:19 PM »
Hi xchcui,

I don't grasp it neither, as I too expect an "oil" to be a liquid. But it could simply be a matter of wording or of translation, meaning "lubricant" in the original language.

The mix of isoparaffins C10-C13 is indeed a solvent, 1 day is a decent time for their evaporation, and they do lubricate a bit like any paraffin despite being too runny. Comparable to kerosene or Diesel oil, which do lubricate when no thicker oil is possible. I believe this mix comes from the alkylation unit of a petrol refinery, which produces some isoparaffins heavier (C10-C13) than is desired as an anti-knocking additive for high-octane gasoline. These heavier isoparaffins are supposedly removed and sold separately. I had already a solvent bottle of them.

What could make the rest? If your key feels dry, it's not a liquid oil nor a grease (for mechanical engineers, a grease is an oil complemented with a soap, usually a lithium salt of a fatty acid).

My bet, nothing more, is a mix of paraffins that are solid at room temperature. They dissolve in shorter paraffins, they lubricate a bit, and won't evaporate too quickly.

Maybe these paraffins a near the liquid-solid limit. But they could also be much longer. For instance thin polyethylene or polypropylene, possibly as a powder, lubricate metals and aren't dirty like graphite or MoS2.

Offline xchcui

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Re: Can a synthetic oil behave as a dry lubricant?
« Reply #2 on: August 18, 2023, 05:48:52 AM »
Hi Enthalpy.

So,if i understood it right,the liquid that i saw on the key the first day could be the isoparaffin solvent C10-C13(mixed with the
dissolved longer paraffin)and one day after,while the solvent(c10-c13)evaporates,the longer paraffin,which are solid in room temperature remain in the cylinder(on the pins/bores/springs).
Those solid long paraffins are responsible for the lubrication of the cylinder and the feeling of a dry lubricant(no liquid residue on the key or cylinder)Am i got it Right?
Just to clear thing up,this is what i expected from a cylinder's lubricant,that it will be dry without leaving liquid residues on the key.
BTW,are the long chain paraffins,that are solid in room temperature and responsible for the dry lubricant feeling,considered as cleaner than the ptfe?(Further to your answer that graphite and MoS2 are dirtier).

Offline xchcui

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Re: Can a synthetic oil behave as a dry lubricant?
« Reply #3 on: August 22, 2023, 12:57:59 PM »
Enthalpy,may you relate to the cleanliness issue
that i mentioned in the end of my post?(the ptfe compare to the liquid-solid paraffin/PP/PE)Thanks.

Offline Enthalpy

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Re: Can a synthetic oil behave as a dry lubricant?
« Reply #4 on: August 23, 2023, 08:46:53 AM »
Hi xchcui!

The solid, long paraffins are just a hypothesis from me. Only an analysis would provide confidence.

Why shouldn't you make low-tech tests, since you have the lubricant at hand? Take a small candle wick, not impregnated with wax. Pour your lubricant generously on it, wait a day, observe. Light the wick outdoors, sniff the odor (be careful)! Burning paraffins smell like wax. Ptfe smells horrible.

Graphite and MoS2 are strongly black or dark grey and look very dirty. Ptfe is slightly white, much more acceptable. Paraffins (among which polyethylene and polypropylene are just extremely long molecules) are transparent at this thickness.

Offline xchcui

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Re: Can a synthetic oil behave as a dry lubricant?
« Reply #5 on: August 24, 2023, 03:36:39 AM »
Hi Enthalpy.
Thank you very much for your help.
Although your answer,as you said about the solid long paraffins,is just a hypothesis,your explanation is very helpful to
understand the issue.
In regards to the test,i guess i can use a cotton balls or
a piece of 100% cotton shirt instead of a candle wick(as i don't have separated candle wick).
This test sound as a simple and effective test,which
can solve my doubts.
Thanks again for your advice an your help. :)
« Last Edit: August 24, 2023, 05:44:33 AM by xchcui »

Offline Enthalpy

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Re: Can a synthetic oil behave as a dry lubricant?
« Reply #6 on: August 24, 2023, 09:22:59 AM »
Make any cotton very compact before lighting it, or it will burn in less than a second and you'll observe no effect by the paraffin. And keep your fingers away. Or use a piece of cloth, of paper - anything easily impregnated, usually a bunch of fibers. I used glass fibers for a huge wick.

==========

I can't resist exposing a similarity with rocket fuels...

"Simple" fuels, as were obtained long ago from refineries, were only separated by distillation. This did not suffice for airplanes and rockets, where the fuel can get really cold, and where it passes through injectors at the combustor. Airplanes needed to remove the water and the "paraffins", understood as dissolved long molecules that precipitate when the fuel is cold and clog the injectors.

Rockets added more requirements because the fuel gets hot in the engine's cooling jacket: lighter components that make bubbles and create badly cooled "hot spots" causing local thermal runaways were banned, as well as multiple bonds that polymerize at heat and have the same effect: boom.

So rockets asked the refineries for a fuel that is especially clean in these aspects. Someone called it wrongly "kerosene" despite the US Rp-1 is close to a Diesel fuel, not to jet fuel, and the Soviet Rg-1 is even denser but some 2s less efficient - more in the direction of boat fuel. Still today, most people repeat without checking that rocket Rp-1 is an aviation kerosene with narrower specs, which is wrong.

Offline xchcui

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Re: Can a synthetic oil behave as a dry lubricant?
« Reply #7 on: August 24, 2023, 02:14:38 PM »
Thank you for your tips about the test options.
And while i am knowing now the chemistry of the long paraffins that are dissolved in shorter paraffin(as you explained before),it was easier to understand your explanation regarding the chemistry of the fuel and its suitability for different aircraft.
Besides that airplanes,rocket and explosions
are always interesting :)
Thanks,again,for the additional information.

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