Advances in Tribological Design of Poly(alkyl methacrylate) Viscosity Index Improvers 2011-01-2123

Fuel economy has become the dominant criterion in the design of new automobiles. The globally enacted targets for fleet average emissions pose true challenges to automobile manufacturers. Increasing fuel economy requires enhancements both in hardware as well as in lubricant performance.

As a key component of the lubricant, poly(alkyl methacrylate) PAMA viscosity index improvers have been identified as crucial design element due to their multiple modes of action. In their original application, they serve the well-known mechanism of polymer coil expansion at high temperatures and collapse at low temperatures. They help to flatten the viscosity/temperature relationship of the lubricant and allow for reduced low temperature viscosities and reduced internal friction, which directly translates into fuel economy.

In addition to this bulk application, interfacial tribological phenomena contribute significantly to efficiency and fuel economy. Poly(alkyl methacrylates), with their versatile chemistry, can be designed with a sequential architecture. Such structures adsorb onto the metal surface as thick polymer layers, and as a consequence reduce friction in the fuel economy relevant mixed lubrication regime of the Stribeck curve.

The present paper now describes how to further fine-tune the tribological design of PAMA film-formers towards particular requirements of the tribo system, might it be lubrication regime (e.g. boundary lubrication), hardware surface (e.g. P-tribolayer, DLC), and component interaction (e.g. vs. poly(isobutene) succinimide PIBSI). With these improvements, the avenue towards broad usage of PAMA film-formers tribo-tailored to the individual fluid constraints in driveline, industrial gear, engine or hydraulic application - has been opened up.