The Difference Between the Role of Friction Modifier and Ep Additives in Lubricant Oil

- Aug 03, 2020 -

Lubricant additives are an indispensable and essential component of lubricating oils, which are used to make up or improve the shortage of lubricating base oils and to give them new properties. A country's lubricant consumption level can reflect the country's economic level and industrial conditions.The friction modifier is an essential part of lubricants.

What is friction modifier?

The friction modifier is usually a straight chain composed of multiple carbon atoms and a molecule with a polar group at the end. Among them, the last group is one of the main factors for the role of the friction modifier molecule. In general, the friction modifier works through physical adsorption and chemical reaction membranes. The lubricating film of the friction modifier that functions through physical adsorption is loosely adhered to each other by orderly and jointly arranged multiple molecular layers. The polarity of the molecules is tightly adsorbed on the metal surface. The formation of the physical adsorption layer is due to the molecular polarity, a friction modifier that dissolves in oil interacts with the metal surface through a strong adsorption force, the top end of the polar group is adsorbed on the metal surface, and the tail end of the hydrocarbon group is dissolved in the oil. It is oriented on the metal surface. All the molecules are neatly arranged in rows, perpendicular to the metal surface, forming a multilayer matrix of friction modifiers. The adsorption layer of this friction modifier is challenging to compress. Still, the hydrocarbon-based tail section is easily sheared during the friction contact process so that it can provide a lower friction coefficient. Friction modifiers that work through chemical reaction films are generally compounds containing metal elements. These compounds can produce a chemical reaction on the lubricated surface to provide a protective film under high-temperature conditions due to boundary lubrication. 


Although the specific reaction mechanism of the lubrication theory community has not been determined so far, from the effect of practical use, these chemical reaction films also have excellent anti-friction performance. In the case where the addition amount of friction modifier is very low, the friction coefficient can be significantly reduced. And this kind of chemical protective film also has excellent shear performance, and the sheared layer can be easily supplemented, which can continuously form a "dynamic balance" of the protective film on the lubricated surface. On the other hand, this kind of friction modifier also often has a particular ability to enhance extreme pressure. At the same time, it can reflect better synergistic performance with other differential friction modifiers, which is also very helpful for improving the PB value and PD value of oil products.

What does friction modifier do?

Energy-saving plays an essential role in alleviating global pressure on energy and the environment. As a kind of energy-saving technology, low friction technology needs further research and improvement. Reducing friction in the use of lubricating oil can be achieved through methods such as improving engine design, improving mechanical materials, and using energy-saving lubricating technologies. Currently, there are two ways to improve the energy-saving effect of lubricants by appropriately reducing the viscosity of the oil and adding a friction modifier. By reducing the friction coefficient between surfaces, fuel economy is improved, and energy loss is reduced. At present, the friction and wear tester and modern analysis technology are mostly used to study the friction reduction performance of friction modifier additives. I have a particular understanding of the production of different friction modifier additives.

Difference between friction modifier additive and EP additives

The difference between the friction modifier additive and the EP additives often causes some controversy, because the friction modifier and the EP additives are mainly used in boundary lubrication conditions, and they will form a physical or chemical reaction protective film on the surface of the friction pair of boundary lubrication.

The main difference between friction modifier additive and EP additives is their different mechanism and performance. Ep additives are generally compounds containing sulphur and phosphorus. These compounds can form a robust lubricating layer under severe load conditions. Boundary lubrication generates a higher temperature typically on the friction surface. These compounds will form a semi-plastic deposit protection film on the surface of the friction pair, which is not easy to shear. Therefore, the EP additives protects the close-contact metal surface and prevents the corresponding surface from being affected. Raised damage. Their primary role is to improve the load and extreme pressure performance of lubricating oil products, that is, the maximum non-seizure load (PB value) and sintering load (PD value), while protecting the friction surface of the engine. However, it is known from many tests and practices that most extreme pressure antiwear agents have little performance in improving friction and reducing friction coefficient.

For the friction modifier, one influential factor that we cannot ignore is the surface temperature of the friction pair, because the temperature can affect the thickness and elasticity of the film of the friction modifier. For physical adsorption membranes, the friction modifier occurs at relatively low heat with the adsorption of the metal surface. If the temperature is too high, enough energy provided by the environment can desorb molecules of the friction modifier from the metal surface and lose its effect.


On the contrary, for the chemical reaction protective film, sufficient surface temperature is required when the friction-reducing effect occurs. It can also be an instantaneous and high friction surface temperature. Only under high-temperature conditions can the chemical reaction be achieved. Form a protective layer. Under the trend of miniaturization and high power of the internal combustion engine and top temperature of the combustion chamber, the friction reducer oil additive capable of generating a chemical protective film will be increasingly valued and widely used.

Liquid moly oil additive

Oil-soluble organic molybdenum compounds have excellent anti-friction properties and can significantly reduce the friction coefficient of moving contact parts. Liquid moly oil additive is the best friction modifier. The moly oil additives currently developed mainly include dialkyl molybdenum thiosulfate (MoDTP), molybdenum dialkyl dithiocarbamate (MoDTC) and trinuclear molybdenum compounds. Although their friction reduction mechanism has not yet been determined, most opinions are that they produce a chemical reaction with the metal surface in the lubrication zone to create a chemical reaction film. A secondary structure film (<50 Dm) is formed on the surface, and MoS and MoO enter the metal surface. MoDTC, MoDTP, and trinuclear molybdenum compounds will decompose MoS on the surface of the micro convex body of the friction surface during the lubrication process. The MoS decomposed gathers in the concave valleys of the surface, thus making the friction surface smooth so that it can last effectively Reduce the friction factor. Liquid moly oil additive is split into organic groups and metallic molybdenum under the influence of higher thermal energy in the friction zone. Molybdenum diffuses on the friction surface and forms a low melting point substance with other metals, which reduces the friction factor and reduces friction losses.

Infomak is dedicated to the technology development of special friction modifier, combined the Technology of nanomaterials developed dry lubricant and oil additives two series. Our products can significantly improve the performance of lubricating oil, improve energy efficiency, effectively protect the lubrication device and extend the oil change cycle, which can satisfy the lubrication oil constantly upgrading for high-end engine oil additives. Contact us.