Oil additives are one or several compounds added to the lubricant to make the grease get some new characteristics or improve some of the existing components of the lubricant. Additives are divided into antioxidants, antiwear agents, friction modifier additives, EP additives, detergents, dispersants, foam inhibitors, corrosion inhibitors, flow point improvers, viscosity index enhancers, etc. The additives sold in the market are generally composite products of the above single additives. The difference is that the composition of the unique additive is different, and the ratio of several separate additives within the composite additive is different.
Clean dispersing additives
1. The clean dispersant means that the lubricating oil can suspend the jelly, carbon deposits and other insoluble materials generated after oxidation in the oil, forming a stable colloidal state and not quickly deposited on the parts;
2. The clean dispersant refers to the jelly, carbon deposits, etc. that have been collected on the engine parts, are washed down by the lubricating oil washing effect. The clean dispersant is a surface-active substance that can absorb solid particulate pollutants in the oil and suspend the contaminants on the surface of the oil to ensure that the oil participating in the lubrication cycle is clean to reduce high temperatures and paint film Formation. The dispersant can disperse the low-temperature sludge in the oil to filter it out in the lubricating oil circulation. Clean dispersing additives are the general term for them. They also have the functions of washing, anti-oxidation, and anti-corrosion. Therefore, it is also called a multi-effect additive. In a certain sense, the quality of the lubricating oil is mainly distinguished by its resistance to high and low-temperature deposits and the formation of paint films. It can also be said that the performance and the amount of detergent dispersant in the lubricant can be seen. The agent has an essential influence on the quality of lubricating oil.
Reasons for adding antioxidants and anti-corrosion agents
Engines using fuel oil, kerosene, gasoline, natural gas or artificial gas, liquefied gas, etc. as fuel must use lubricants to lubricate their moving parts. The lubricating oil should be in contact with air during use, and various mechanical equipment will also generate heat, which will increase the temperature of the friction part during operation. Besides, various metal materials in the equipment, such as copper and iron, will play a catalytic role. The oxidative deterioration of oil products will eventually increase the viscosity of the lubricating oil, generate acidic substances to corrode metal materials, and also generate various carbon-like or asphalt-like precipitated substances such as paint films to block the pipeline. All these changes will adversely affect the continued use of oil products and the normal operation of the equipment. Therefore, oil products are required to have good anti-oxidation and anti-corrosion properties. Adding anti-oxidation and anti-corrosion additives to the oil, its purpose is to inhibit the oxidation of the oil, passivate the catalytic effect of the metal on the oxidation, and extend the use of the oil and protect the machine.
After a certain refined base oil, it has a certain anti-oxidation effect. Still, it can not meet the extremely demanding use requirements of modern times, and antioxidant and anti-corrosion additives must be added. The amount of addition is second only to the clean dispersant and viscosity index improver, ranking third.
Pour point depressant mechanism
Pour point depressant is a chemically synthesized polymer or condensate, which generally contains polar groups (or aromatic nuclei) and alkyl chains similar in structure to paraffin hydrocarbons in its molecule. Pour point depressant cannot prevent paraffin from crystallizing out at a low temperature, that is, the cloud point of the oil remains unchanged, it changes the shape and size of the wax crystal by adsorption on the wax crystal surface or eutectic with the wax to prevent the wax from forming a three-dimensional network structure so that it still maintains the oil's ability to flow at low temperatures. It should be emphasized that the pour point depressant can only play the role of pour point depressant in oils containing a small amount of wax. There is no pour point depressant effect if the oil contains no wax or contains too much wax.
Antirust and antiseptic mechanism
Rust inhibitor is a very polar compound. Its polar group has a strong adsorption force on the metal surface, forming a tight monomolecular or multimolecular protective layer on the metal surface to prevent the corrosion medium from contacting the metal. To anti-rust effect. Besides, the base oil that dissolves the rust inhibitor can be adsorbed in the place where the rust inhibitor has little adsorption and penetrates between the anti-rust additive molecules. With the help of van der Waals force and the additive molecules, the adsorption film is stronger; besides, due to the foundation, The role of oil makes the adsorption of the additive on the metal surface firmer and not easy to separate. The oil can also form a concentrate with the additive, thereby making the adsorption membrane more compact. In short, these functions of the base oil are beneficial to protect the adsorbed molecules, maintain the thickness of the oil film, and play a certain role in preventing rust.
Friction modifier additive
Friction modifier additive refers to an additive that reduces the friction coefficient of lubricating oil under boundary lubrication conditions. Its role is to form a layer of lubricating protective film on the metal surface to avoid direct contact between metal peaks, so that mixed lubrication and boundary lubrication The coefficient of friction decreases, reducing frictional resistance and wear and achieving fuel savings.
Antiwear agent
The antiwear agent refers to the ability of the lubricant to form a film on the friction surface under light load and medium load conditions to prevent wear. Such as: sulfurized grease, phosphate ester, dithiophosphate metal salt.
EP additives
EP additives refer to the ability of the lubricant to prevent sintering and scratching of the friction surface under low-speed high-load or high-speed impact load friction conditions, that is, under so-called extreme pressure conditions. EP additives mostly contain sulfur, phosphorus, chlorine and other active substances. Extreme pressure agents react chemically with metals on the friction surface to generate compounds with lower shear force and melting point than the original metal, forming an extreme pressure solid lubricating film to prevent sintering.
Antifoaming agent
In the use of lubricating oil, it is often affected by shocks, agitation, etc., which causes air to enter the lubricating oil, so that the formation of air bubbles will affect the lubricating performance of the lubricating oil, accelerate the oxidation rate, cause oil loss, and hinder the transmission of oil. Interrupt the oil supply, hinder lubrication, and affect the pressure transmission of hydraulic oil. The antifoaming agent is mainly used to suppress the generation of foam and increase the speed of eliminating foam so as to avoid the formation of stable foam. It can be adsorbed on the foam, forming an unstable film, so as to achieve the purpose of destroying the foam. The most commonly used antifoaming agent is methyl silicone oil antifoaming agent
Antioxidant
An important additive to prevent the aging of oil products can effectively increase the service life of oil products. Also talk about the solid additives commonly used in the market
There are many additives in the market that claim to improve the protection of engine oil, and different brands use different mechanisms of action to advertise. The following briefly introduces several types:
(1) Graphite and molybdenum disulfide solid suspension type mainly play the role of anti-friction and antiwear, but can only be applied to solid lubrication and low-speed large-load equipment, and they have no effect when the engine speed exceeds 1000r / min. In addition, its state in lubricating oil is unstable, and precipitation will occur under certain time and temperature conditions. Its precipitates can cause blockage of the oil circuit and accelerate the formation of sludge.
(2) The PTFE resin particulate type has been widely used as an antiwear additive in the United States, but it will deposit on the oil passage and the oil pump filter at low temperature to cause blockage, and deposit in the piston ring groove to make it inactive and accelerate sludge. It is rarely recommended for use in the United States.
(3) The coatings containing heavy metal particles such as copper and lead can form a metal film on the friction surface, which plays the role of antiwear and anti-extreme pressure, but an oil filter with a slightly larger filter core pore size must be used, otherwise it will be filtered out , Block the oil pump and oil circuit. In addition, it will form a film on the surface of the piston and the cylinder for a long time, which will cause the two to stick together, which is prone to sticky rings and other phenomena.
(4) Magnetic olein is a surface metal magnetizing agent, which mainly plays the role of reducing friction and antiwear. The effective time of this type of product is too short, it needs to be added continuously, the cost is higher, and it will interfere with the normal operation of the electronic components on the car.
(5) Chlorine-containing type "Chlorine" is a good extreme pressure agent. Still, it is not suitable for the high-temperature and high-speed working environment of the engine, and it will generate acid under suitable conditions, which is potentially dangerous to the metal in the engine. Besides, chlorine additives may have matching problems with additives already in the lubricant, causing other side effects.
(6) Lead-free, fluorine-free, and chlorine-free chemical film-forming agents can simultaneously exhibit extreme pressure resistance, oxidation resistance, and certain abrasion resistance. Due to its long-lasting chemical reaction film formed on the metal surface, it can effectively extend the life of lubricating oil and metal parts.
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