Volume 4, Issue 10 (November 2007)
Design of Functionalized PAMA Viscosity Modifiers to Reduce Friction and Wear in Lubricating Oils
Polyalkylmethacrylates (PAMAs) are widely used as both viscosity index improvers and dispersant boosters in engine, hydraulic, and transmission oils. Since they are employed in a relatively high concentration in these roles, it is desirable that they be able to enhance other characteristics of a lubricant and, in particular, its boundary lubricating properties. A series of functionalized PAMAs have been synthesized that can adsorb from oil solution onto rubbing surfaces to produce thick boundary films. These films enhance lubricant film formation in slow speed and high temperature conditions and thus make a significant contribution to their lubricating ability. The current paper describes a systematic study of the influence of functionalized PAMAs on boundary lubrication performance. The high frequency reciprocating test rig (HFRR) was applied to investigate friction and wear under pure sliding. A new test method has been developed which allows wear to be monitored in a rolling and sliding contact based on the mini traction machine (MTM). This, in combination with other tests, is employed to investigate the influence of polymer architecture, functionality, concentration and molecular weight on friction and wear in a range of lubricant formulations. This enables the tailored design of polymers which offer low friction and wear properties.