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Formulation of industrial lubricants requires the selection of a number of different additive types such as antioxidants, corrosion inhibitors, defoamers, emulsifiers, extreme pressure (EP) agents, lubricity additives, pour point depressants and viscosity index (VI) improvers. Within each category, the formulator is also faced with having to select specific chemistries for use in preparation of the lubricant.
This leads to concern from a formulation standpoint about whether the additive will not only provide the required performance but also how it will impact the other components in the formulation. This is a major issue that lubricant compound/blenders must deal with on a daily basis.
TLT conducted a readership survey in mid-2007 and asked readers which additive type has the greatest impact on the performance of their lubricants and which additive class they would be most interested in learning more about. Overwhelmingly, reader response was that EP additives have the greatest impact on lubricant performance. The survey indicated that readers wanted to learn more about this additive type in order to better understand how to use them in formulations.
TLT sought interviews with the industry's key additive manufacturers to gain insight on this additive class. The five EP suppliers who agreed to talk are, in alphabetical order, Arkema, Dover Chemical, Lubrizol, Rhein Chemie and Rhodia.
An initial discussion was held to provide basic information on how EP additives function and the various technologies available to the formulator.
What is an EP additive?
Lubricants operate in the boundary between moving metal parts to prevent the contact that could lead to an increase in friction, increase in wear and eventually welding. The classic type of component used to prevent these phenomena is a boundary lubricity additive.
The boundary lubricity additive typically functions by adsorbing on the metal surface to form a film that will reduce metal-to-metal contact. This function is achieved because the boundary lubricity additive has a polar head group that can interact with the metal surface and a tail group that is compatible with the lubricant carrier (mineral oil, synthetic basestock or water). A classic example of a boundary lubricity additive is an ester which could be available as a natural product (canola oil, lard oil, tall oil fatty acid, etc.) or as a functionalized molecule (monobasic ester,...