An ash-free organic thickener made by reacting isocyanates with amines. Polyurea greases resist oxidation and last a long time hot, which is why motor builders fill sealed and shielded bearings with them. They clash with many soap greases: mixing polyurea with lithium often softens the blend sharply until it runs out of the bearing. Shear-stable grades exist, but some polyureas soften sharply when worked and others harden in storage.
Motor shop packed these with polyurea, so the lithium complex in your gun can't go in here.
Most electric motors leave the factory on polyurea, so check the motor data sheet before the first regrease.
Also heard as
- urea grease
- diurea
Related terms
Thickener
Solid structure in a grease, usually a metal soap or polyurea, that holds the base oil like a sponge.
Grease compatibility
Whether two greases can be mixed without losing consistency, dropping point or stability.
Soup
Grease that has broken down or been mixed with an incompatible type and turned runny.
Lithium complex
Grease thickener made from a lithium soap plus a complexing acid, the all-purpose bearing workhorse.