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Grease Thickeners

Grease Thickeners

Grease Thickeners

(OP)
Lubricants are not my field but I came across a list of thickeners for grease.One of them was silica.Maybe I'm missing something but how can you use silica,very abrasive , in a lubricant ??

RE: Grease Thickeners

Beats me.  Here is a description of silicone grease, uses silicon oil as base lubricant and thickener based on "fumed silica"
http://en.wikipedia.org/wiki/Silicone_grease

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RE: Grease Thickeners

... if you follow think link for silica fume above you see

Quote:

Silica fume consists of very fine vitreous particles

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RE: Grease Thickeners

(OP)
Thanks. The magic term is then 'silica fume' which is very fine amorphous [non-crystalline ] SiO2 .That should have little abrasive action.

RE: Grease Thickeners

I read the link Unclesyd gave.  While well written and informative, I think he left out one important thing.  Greases should never be mixed.  Mixing can and most often does cause the lubricants to separate from the soaps causing lubrication failure.

rmw

RE: Grease Thickeners

all "lubricating greases" can technically be called a "gel" - a lubricating fluid with a colloidal suspension of a thickener in it that gives the grease its structure. the thickener can be a metal soap (as in the most common greases) but it is also possible to make a grease with more exotic thickeners, eg silica or "claybased" compounds. in the case of silica it is not just ordinary "sand" but a very specific compound with very small dimensions without sharp (and abrasive) edges. the amount used is usually about 5-10 %, the rest of the grease is nearly all base oil or another type of fluid that can be used as a lubricant, often some extra additives (antioxidant, antiwear) are included. the type of thickener has a large influence on the behaviour of the grease - depending on the type used you may end up with a very "thick" grease or a semifluid grease. due to the colloidal structure greases usually have a nonnewtonian character. of course when you add a lot more "thickener" into less fluid the mixture can be very abrasive, as you can see for example in the dredging industry where sand dissolved in water (also a "gel") is pumped through pipes. usually the impellorblades in the centrifugal pumps that are used, only last for about a week and then need to be reconditioned over the weekend...

RE: Grease Thickeners


Hi.

For greases to work, as you're aware, there are a number of  rheological requirements to be met.  

Parameters include: adherence, retention of properties under both shear & temperature, and some degree of fluidity.  (More viscous materials risk more "work", especially in start-up.)

What kind of grease are you using?  Generally, heavier duty greases integrate bases like ISO 460 (SAE 140).  Thickeners can include: soaps of lithium, sodium, calcium (hydrated and anhydrous, polyurea and clay.  

For more information, I'd look to The National Lubricating Grease Institute (NLGI): http://www.nlgi.com.

Good luck!

 

William Gunnar
http://www.IndustrialCoatingsWorld.com
 

RE: Grease Thickeners

Interestingly enough, there's much more concern about mixing greases than mixing oil viscosities.

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