Machinery Lubrication

Machinery Lubrication November December 2015

Machinery Lubrication magazine published by Noria Corporation

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www.machinerylubrication.com | November - December 2015 | 51 lubricant's objective is to reduce friction and wear. However, there are many situations in which a certain amount of traction friction is required for equipment to operate properly. The friction modifiers used in these applications are not intended to increase or decrease friction but to act differently under specific shear conditions. This essentially smooths the transition from a dynamic condition to a static condition, such as during a gear change in a transmission or the engagement of a clutch. The vast majority of friction modifiers in use today are designed to reduce friction or increase lubricity for better fuel economy. Recently, the U.S. government increased fuel economy standards with the goal of raising the Corporate Average Fuel Economy (CAFE) to 54.5 miles per gallon. This number, which is double the current standard, is for gasoline engines only, but there is a similar push for diesel engines as well. One way to achieve this goal would be to reduce the viscosity of the engine oils in use. The challenge is lowering the viscosity while maintaining a sufficient lubricant film to reduce wear and friction. Great strides have been made in engineering to lower the friction generated in an engine. This has increased fuel economy. There have also been many advances in lubricant technology, including in the development of friction modifiers. Friction modifiers are most efficient under boundary conditions or where metal-to-metal contact occurs. Organic friction modi- fiers have long, soluble chains and a polar head. The polar head attaches to the metal surfaces. The soluble chains line up beside each other much like fibers in a carpet. The polar heads may be comprised of phosphoric or phosphonic acids, amines, amides or carboxylic acids. The soluble chains form dense mono layers or thick, reacted viscous layers. These layers shear easily and create a relatively slippery surface. Organic Friction Modifiers Mechanical types of friction modifiers form layers of platelets that align with one another, providing a reduction in friction. The most common of these is molybdenum dithiocarbamate (MoDTC). These additives reduce friction by forming nano-sized single sheets dispersed Friction Modifiers Oil Oil Oil Oil Oil Oil Oil Oil Oil Strong anti-compressive behavior helps to separate surfaces Polar head attracted to surface

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