Multifunctional polymer additives for lubricating oils

Requirements regarding the less harmful emissions and increasing fuel efficiency of internal combustion engines govern the development of modern lubricating oils towards lower viscosity grade and multi-functional, highly efficient additives. Here, two additives, namely viscosity index improvers and friction modifiers play the most important role. Among the polymeric additives commonly used as viscosity index improvers, poly(alkyl methacrylates) (PAMA) provide the easiest way of changing the composition and structure that are necessary to comply with the new engine oil specifications. PAMA additives are manufactured by the free radical copolymerization of corresponding methacrylate monomers in solution of lubricating base oil. Therefore, they can relatively simply be chemically modified by the addition of different functional methacrylate comonomers because of similar copolymerization reactivity. This is their noteworthy advantage over the competing additives such as polyolefins or styrene/butadiene/isoprene copolymers that are prepared by metallocene or anionic polymerization where chemical modification is a much more complicated and demanding process. In addition to the viscosity index improving, the additives based on PAMA are well known and widely used pour point depressants of lubricating oils. They prevent gelation of the oil and deposition of n-paraffins from the base oil at low temperatures and enable oil to flow at much lower temperatures. This paper will present the results of synthesis and properties of new dispersant PAMA additives of improved solubility, shear and thermal stability, while maintaining excellent properties of improving the viscosity index and lowering the pour point of lubricating oil.