Search Results

Viscosity index improvers based on poly(alkyl methacrylates) as well as polyolefins have been well known to the industry as key additives to formulate lube oils for decades. Recent efforts to combine these two chemistries to prepare well-defined comb polymer architectures have led to a performance breakthrough. Specifically, the concept of temperature dependent comb polymer coil expansion and collapse allows to achieve extraordinary viscosity temperature properties. Viscosity indices and thickening efficiencies are well beyond the levels achievable by conventional chemistries at the same shear stability level. After a general introduction of viscometric key properties, the paper describes synthetic pathways towards these novel comb polymers. Standard radical polymerization of polyolefin macromonomers with alkyl methacrylate backbone comonomers is the most straightforward process for their preparation, and allows for an easy transfer to manufacturing.

Polyalkylmethacrylates (PAMAs) are widely used as viscosity index improvers and dispersant boosters in engine, transmission and hydraulic oils. They have been shown to be able to adsorb from oil solution on to metal surfaces, to produce thick, viscous boundary films. These films enhance lubricant film formation in slow speed and high temperature conditions and thus produce a significant reduction of friction and wear. In a recent systematic study a range of dispersant and non-dispersant PAMAs has been synthesized. The influence of different functionalities, molecular weights and architectures on both boundary film formation and friction has been explored using optical interferometry and friction-speed charting. From the results, guidelines have been developed for designing PAMAs having optimal boundary lubricating properties. In the current paper the film forming, friction and wear properties of solutions of two functionalised PAMAs is first described.