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Oil additives are additives that reduce the coefficient of friction of lubricants under boundary lubrication conditions. Lubricant energy-saving anti-friction additives appearing on the market generally belong to this kind of additives. In the fluid lubrication state, the surface of the Friction pair is entirely separated by the lubricating oil film. The friction force is proportional to the viscosity of the lubricating oil. The higher the thickness, the more excellent the viscous resistance. However, if the width of the lubricating oil is too low or the load on the friction pair is high, the lubricating film between the friction pairs is fragile, and the fluid lubrication state cannot be maintained. The boundary lubrication state of the direct contact of the friction pair is formed. The friction force is not related to the viscosity of the lubricating oil, but only depends on the chemical properties of the lubricating oil, that is, the surface-active substances present in the lubricating oil. Since most of the original surface-active materials in the lubricating oil are refined and removed during processing, it is necessary to add a Friction modifier additive to improve the lubricating performance of the refined oil. Friction modifier additive is based on this principle. Through the chemical action of the additives, the micro convex parts of the friction surface are softened and smoothed, or the additives are adsorbed on the surface of the friction pair, and the micro concave portions are filled to improve the state of the oil film on the surface of the friction pair. The friction force is reduced under severe boundary lubrication conditions, which can enhance the power, lower fuel consumption, and reduce wear. Friction modifier additive filling the depression can also improve the sealing of the combustion chamber of the engine and maintain the proper technical condition of the engine. Friction modifier additive is divided into solid suspension type and oil-soluble type.
1.Solid suspended lubricating oil additives
The robust suspension type was developed and applied earlier, and it is dispersed in the lubricant in the form of particles. The most famous solid suspension additives are molybdenum disulfide, graphite, and Teflon powder. Molybdenum disulfide and graphite are multilayer lamellar crystals. They have a strong adsorption force on the metal surface, but the interlayer shear resistance is feeble, so they have an excellent anti-friction and anti-friction effect in the boundary lubrication state. Resistant to high temperatures. Teflon powder is generally considered to be unable to form an adsorption film on the metal surface, but its particles can accelerate the running-in of the friction pair surface under boundary lubrication conditions, improve the smoothness, and reduce friction. The disadvantage of solid suspended oil additives is that the particles of lubricating oil additives may aggregate and delaminate during storage, and its anti-friction effect will be reduced. At the same time, the lubricating oil will become cloudy, the color will be darkened, and the appearance will be damaged. Most critically, there is also the possibility of particles clogging the filter or being separated from the lubricant by a centrifugal filter.
2.Oil Solubl lubricating oil additives
Due to the inherent disadvantages of oil-soluble lubricating oil additives, such additives have been gradually phased out in recent years. Vigorously develop oil-soluble lubricating oil additives that are entirely compatible with lubricating oils. Most of these lubricating oil additives are polar or active oil-soluble macro molecular compounds, such as fatty acids. In oil solution, a dimer molecule pair with extreme groups bonded to each other is formed. When the contact between the extremist group and the metal surface is much higher than the inter molecular dimer force when in connection with the metal surface, the dimer is gradually separated into single Molecules, and form a firm, tight, directional first adsorption layer on the metal surface and even hundreds of odd molecular layers. When the metal surface moves relatively under pressure, the end of the non-polar hydrocarbon chain of the directional molecule in the boundary adsorption layer on the isolated metal surface is relatively easy to slide relatively, the friction loss is small, and the friction coefficient may be as little as 0.01-0.02. It has a strong resistance to the pressure of the vertical metal surface. The more polar the lubricating oil additives are, the longer the hydrocarbon chain and the better the lubricating ability. The adsorption force between polar compound molecules and metals decreases with increasing temperature. When the oil temperature reaches 150-200 ° C, the polar molecules fall off, and the adsorption film is destroyed and fails.
In recent years, oil-soluble lubricating oil additives use compounds such as organic molybdenum, organic tungsten, natural boron, and ashless organic esters as friction modifiers, which not only have anti-friction properties at ordinary temperatures but also can react chemically at high temperatures. Improve the condition of the friction surface, make the friction surface smoother, and the friction coefficient is about 0.05. Although friction reducer oil additive often has both antiwear effects, it is different from antiwear and extreme-pressure antiwear additives. Friction reducer oil additive forms a friction-reducing adsorption film or a friction-improving film under boundary lubrication conditions. The role of antiwear agents or EP additives is to protect the friction surface from sticking, seizing or sintering when the lubricating film is broken, and its active chemical elements (sulfur, phosphorus, etc.) chemically react with the metal to form an antiwear protective film. The antiwear film can support higher loads than the boundary lubrication film, but the friction coefficient is much larger than the boundary lubrication film.
For automobiles, the boundary lubrication mainly occurs in the piston ring of the engine and its corresponding cylinder liner at the top dead center, and the surface of the main reducer gear. Besides, crankshaft bearings and connecting rod bearings will experience boundary lubrication when the engine starts, stops, and accelerates under heavy load or suddenly loads at a certain speed. When the camshaft and lifter, rocker arm and valve lifter of high compression ratio engine valve mechanism are operating under heavy load, the friction surface is also in the state of boundary lubrication. Therefore, adding appropriate friction reducer oil additive to automobile lubricating oil is an effective measure to reduce friction and save fuel. The fuel-saving rate is generally between 1% and 4%.
Antioxidants and antiseptics can inhibit oil oxidation and are mainly used in industrial lubricants, internal combustion engine oils, and process oils. A metal passivation agent is also an antioxidant. It does not have an antioxidant effect, but indirectly "passivates" metal activity, inhibits the catalytic effect of metals and their compounds on the oxidation of oil products, reduces oil damage, and prolongs oil life.
EP additives are additives that can form a high melting point chemical reaction film with metal surfaces under high-temperature and high-pressure boundary lubrication conditions to prevent melting, seizure, and scratching. Its role is to react its decomposition products with metals at high friction temperatures to produce compounds with lower shear stresses and melting points than pure metals, thereby preventing contact surface seizure and welding and effectively protecting metal surfaces. EP additives are mainly used in industrial gear oil, hydraulic oil, guide rail oil, cutting fat, and other oils with extreme pressure requirements to improve the intense pressure and wear resistance of oil products. Any additive that can make the lubricating oil increase the strength of the oil film, reduce the coefficient of friction, improve the antiwear ability, and reduce friction and wear between moving parts is called an oil-based agent.
Viscosity index improvers are oil-soluble, chain-like polymers with a relative molecular mass of tens of thousands to millions. When they are dissolved in the lubricating oil, they exist in the form of filaments at low temperatures, which has little effect on the viscosity of the lubricant. As the heat of the lubricant increases, the threads expand the effective volume increases and the resistance to the flow of the grease. The growth leads to a relatively significant increase in the viscosity of the oil. Based on the fact that viscosity index improvers have different forms and have different effects on thickness at different temperatures, they can increase viscosity and improve viscosity-temperature performance. Therefore, viscosity index improvers are mainly used to increase the viscosity index of lubricants, improve viscosity-temperature performance, and increase viscosity. It can be used to formulate thickener oil so that the formulated oil has excellent viscosity-temperature performance, makes it good at low-temperature stability, low fuel consumption, and has a specific antiwear effect. The role of the preservative is to form a strong adsorption film on the metal surface to suppress the contact of oxygen and water, especially water, on the metal surface so that the metal will not rust.
Rust inhibitors are mainly used in industrial lubricants and metal processing cooling lubricants, metal protective oils, etc. After the oil temperature drops to a certain level, it will lose fluidity and solidify. The function of the pour point depressant is mainly to reduce the freezing point of the oil and ensure that the oil can flow at low temperatures.
Pour point depressants are widely used in various types of lubricating oils. Typical representatives are alkyl naphthalene and poly-α-olefins. Oil products such as hydraulic oil and compressor oil may encounter the working conditions of normal start up and shutdown, and the circulation system of internal combustion engine oil, gearbox oil, and other agitation is more intense, often generating a lot of foam, causing energy transmission and oil supply failure. There are many anti foam methods, which can be divided into physical-mechanical anti foam and chemical anti foam. Most of the substances that are additives as anti foaming agents should have: a. Anti foaming agents cannot be dissolved in the lubricating oil; b. Anti foaming agents can be evenly dispersed in the lubricating oil; c. The surface tension of anti foaming agents is higher than that of lubricating oils small.
With the continuous improvement of the quality level of lubricating oils, Car Engine Oil Additives have included a variety of surface-active additives, such as antioxidants and antiseptics, metal salt detergents, dispersants, extreme pressure anti wear additives, and rust inhibitors. Test balance will not cause mutual interference and synergy between various additives. If an inappropriate engine additive is added again, it may be affected by the interference between different additives, and their regular performance may be modified, especially for high-quality G-class and higher engine lubricants, which cannot be ignored. Therefore, the selected car engine oil additives must be compatible with the original additives in the lubricating oil to properly exert its energy-saving and anti-friction effect. For the user, after adding energy-saving anti-friction agent in the lubricating oil, it is best to observe the lubricating oil frequently to grasp the change of its condition for a long time.