Film strength

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I have too many question about film strength:

It is said that synthetic basestocks have higher "film strengt" than conventional basetocks. Is that because of their uniform molecule structure, allowing "all" the H-atoms of one molecule to interact with H-atoms of the neighbor molecules?

Do the electrostatic properties of an ester result in an apparently high film strength or is film strenght only the result of the interaction between the molecules?

How do VII's effect film strength (not shear stability)? Comparing the film strength of let's say 2 PAO-based oils (unadditized). The one has an SAE 10w-40 viscosity, the other uses a "thinner" basestock and more VII's => SAE 5w-40. Would the SAE 10w-40 theoretically have the higher film strength?

Is the HTHS-viscosity a good indicator of the film strength, or is there no relation between filmstreng and this kind of dynamic viscosity?

Another confusing thing:

Fuchs Silkolene's statement about PAO from:

http://www.silkoleneoil.com/techtip4.htm

"In fact, on their own they are hopeless 'boundary' lubricants, with less load carrying ability than mineral oil".

Isn't "load carrying ability" the same as film strength?

How much does film strength matter when it comes to hydrodynamic lubrication, is the HTHS more interesting here?

Anyone, please help me "self studying" lubrication, thanks
smile.gif
 
"Isn't "load carrying ability" the same as film strength?"

In my mind Film strength would be used in a hydrodynamic application and load carrying would be in a gear or impact application that said I use both terms right or wrong as the same meaning or as least hand in hand.

I would say a good way to test base oil load carrying or film strength maybe using a pin on disk machine to messure the co efficient friction
as I remember the best were vegtable oils and esters and the worst were PAO and GPII and GPIII
oils.

VII will add to the HTHS numbers an as such
may add to the Load carrying but effect would be very small IMHO.

HTHS vis is a kind of mesurement of film strenght a higher HTHS vis the faster and thicker a oil "wedge" will form in a hydrodynamic bearing.

others can offer more insight to this
bruce

bruce
 
From oronites web page:

FILM STRENGTH - See lubricity

LUBRICITY - ability of an oil or grease to lubricate; also, called film strength. Lubricity can be enhanced by additive treatment. See compounded oil.
 
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