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I have seen a few compatibility charts that show a polyurea shear stable and a polyurea conventional grease. The shear stable variety is compatible with lithiums and other greases where the conventional is not.

Can someone point me to a manufacturer or brand name? I have looked all over and so far have come up empty. Thanks.
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"Shear stable" is a relative term with polyureas. It's not on the very top of their bag of tricks. I'm also not sure I'm ready to get in the boat with you on the generic assessment of compatibility. I'd want to see the results of a study between the two specific greases of interest. As Li-complex greases progress, they are evolving into the "O+" of grease - the universal donor, or as close as we may get.
quote:
Originally posted by rustyB:
I have seen a few compatibility charts that show a polyurea shear stable and a polyurea conventional grease. The shear stable variety is compatible with lithiums and other greases where the conventional is not.

Can someone point me to a manufacturer or brand name? I have looked all over and so far have come up empty. Thanks.


I think BP, under the brands Castrol Tribol, Castrol Optimol and/or Aral should have something for you. It will all depend on application and type.

Cheers,

PA
Hi Rusty
High Quality Polurea Greases are manufactured by Japanese Grease makers, don't know brands,
In the USA Exon Mobil, was Witco, and Shaffer, now Shell, there are others but these were pointed out to me by Dave Nash of Witco 15 years ago as the top three manufacturers and since then we have used the Exon Mobil ISO 220 base oil with very reliable results.
I do prefer the Exon Mobil products as they utilise a Passive EP system, CaCO3, no reactivity with moisture very passive grease,
Polyureas are not shear stable as they tend to "drop" the base oil under sever loading and once the pressure is remove the thickner will recombine with the base oil without too much change in the grease.
Noria (I think) has a chart on compatibility with other thickners and the polyurea tends to be the thickner that can handle some contamination from other grease thickners but when ever mixing any grease type the system should be pruged or repacked so + 90 % of the old product is removed, I'll check if I can find the chart and pop it up.


Regards


Rob S



www.rttech.com.au

We
RustyB,

Polyurea is a group name just like lithium complex and calcium greases. There are many different versions that all fit the family descriptor. For polyureas there are two kinds which dominate and those are often referred to as tetra-ureas and di-ureas. Di-ureas are much more shear stable than tetra-ureas.

Compatibility will depend on type of PU. Compatibility for di-ureas are better than for tetra-ureas but if or not to mix two thickeners is not always a question of chemical compatibility. If you are converting from a product with excellent shear stability to a product with poor shear stability, leakage may falsely appear to be a result of incompatibility.

Good advise is to be cautious with thickeners having borderline compatibility such as PU. Run a compatibility test if you are uncertain.

You can also make a risk assessment of your application. If the product is to be used in an application with low shear and low strain incompatibility may not be an issue.

Be extra cautious in medium to high speed applications, vibrating housings, housings exposed to shock loads, high temperature applications and housings with high filling ratios >50% or housings without drain holes or double lip seals.

Stamina brand show fairly good compatibility with lithium complex greases.

Cheers,
GG

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