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  • 1. Crystal structure and lubrication mechanism of tungsten disulfide WS2

    The crystal structure of WS2 is a typical hexagonal crystal layered structure. Each layer is composed of two layers of hexagonal sulfur atoms sandwiched by a layer of metal tungsten atoms, and sulfur atoms and tungsten atoms form a triangular cone shape. The sulfur atoms and tungsten atoms in each segment are connected by strong covalent bonds, and the layers are combined by relatively weak Van der Waals forces. This kind of connection makes the sheet have a substantial sliding property, and sulfur atoms can quickly form physical or chemical adsorption with most metals to create a transfer film. Friction mostly occurs between the lubricating film and the transfer film, so although conflict alone may not occur Wear, and the damaged part of the film layer can be repaired by moving the lubrication film that adheres to the lubricating material and the WS2 debris accumulated on both sides of the friction part. The SEM electron micrograph of the hexagonal layered sheet-like WS2 is shown below.

    2. The characters of tungsten disulfide WS2

    WS2, as a solid lubricant has significant characteristics in terms of physical properties. In the past, petroleum base oils and greases were most commonly used as lubricants.

    In recent years, with the advancement of industrial technology, the demand for new reliable lubrication has increased with the increase in machine output, rotational speed, sliding speed, load, and use in harsh environments such as high temperature and vacuum. It is also essential to maintain a clean atmosphere and protect the environment.

    The oxidation temperature of WS2 is about 100℃ higher than that of molybdenum disulfide (MoS2), which has an excellent heat resistance and extreme pressure performance, and has a low coefficient of friction;

    WS2 can resist high surface pressure;

    In solid lubricants, its friction coefficient has a tendency to decrease with increasing load;

    WS2 also has lubricity at a high temperature of 450℃, which helps prevent sintering or seizure;

    WS2 is more resistant to wear;

    WS2 can reduce industrial waste and protect the environment;

    WS2 has a perfect energy-saving effect;

    In addition to reducing energy consumption by reducing the friction coefficient, WS2 can also extend the service life of components, achieve energy saving and reduce costs;

    It acts as a lubricant in the temperature range from -273℃ to 450℃ in the air;

    WS2 is compatible with most oils and greases;

    Compared with graphite, MoS2 and PTFE, WS2 reduces surface deposits by half.


    3. Product use examples of tungsten disulfide WS2 

    The use of 3-5% WS2 in the brush can effectively extend the life of the brush by 20%-40%; especially suitable for power tools and household appliances, the effect is significant;

    The addition of 5-10% WS2 to the graphite mechanical seal ring can effectively reduce the wear rate and extend the life by more than 30%;

    WS2 can also be used for mould release agent;

    Lubricants for ball bearings and roller bearings;

    Engine and driveline components;

    Air vibrator, pneumatic motor electrical connector;

    Circuit breakers and switches (super electrical contact material additives);

    Electric motor

    Lubricants for industrial gears and bearings;

    Pilot valve, chain saw, etc.;

    Rubber gasket, O-ring;

    Satellite and aircraft parts;

    High vacuum application products;

    Cryogenic pump seals, etc.

     

    4. Performance data comparison chart of tungsten disulfide WS2

    Although WS2 has a very similar layer structure to graphite and MoS2, its lubricating performance has a particularly special meaning. It has a thicker layer and a more stable molecular structure, which is different from graphite. It is more lubricated under vacuum conditions;

    WS2's performance is better than MoS2, and it can continue to lubricate in a wet environment.

    Friction as a function pressure.png

    Comparative Oxidation Rates of MoS2 and WS2.png

    Infomak is dedicated to the technology development of special oil additives, 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. 

    If you are looking for  WS2, please feel free to contact us.


    Aug 04
    2020
  • 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.

    oil additives.jpg

    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.

    Graphite.jpg

    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.

    Infomak is dedicated to the technology development of special oil additives, 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.

     

     

     

     


    Aug 03
    2020
  • Molybdenum disulfide (MoS2) is a critical powder lubricant.

    The working environment of lubrication and anti-friction is often not a single requirement. Many institutions are developing molybdenum disulfide (MoS2) composite lubricating materials, which can provide the required lubrication performance and corrosion resistance according to different working conditions. Anti-oxidation performance, anti-impact performance, high-temperature resistance, salt spray resistance and other composite functions.

    Molybdenum disulfide powder is made from natural molybdenum concentrate powder after chemical purification. The colour of the product is slightly silvery grey, with a metallic lustre, it has a greasy touch, and is insoluble in water. Molybdenum disulfide powder has the advantages of excellent dispersibility and non-stickiness. It can be added to various greases to form a non-sticky colloidal state, which increases the lubricity and extreme pressure of the lubricant; it is also suitable for high temperature, high pressure and high speed, High-load mechanical working state, extend equipment life. The primary function of MoS2 for friction materials is to reduce friction at low temperatures and increase resistance at high temperatures, and the loss on ignition is small.

    MoS2 structure.jpg

    MoS2 is widely used as a good powder lubricant, and the following working conditions are applicable:

    1. Lubrication under broad temperature conditions

    The applicable range of lubricating oil and grease is about 60 ℃ to 350 ℃. MoS2 powder lubricant can be used in the operating temperature range of 270 ℃ to 1000 ℃.

    2. Lubrication under heavy load

    Generally, the oil film of lubricating oil and grease can only bear a relatively small weight. Once the pressure exceeds its limit, the oil film will rupture, and the friction surface will bite. The MoS2 powder lubricant film can withstand an average weight of 108Pa.

    3. Lubrication under vacuum

    Under high vacuum conditions, general lubricating oils and greases have a greater vaporability, which can easily damage the vacuum environment and affect the working performance of other components. MoS2 powder lubricant is generally used for lubrication.

    4. Lubrication under radiation conditions

    Under radiation conditions, general liquid lubricants will polymerize or decompose, losing lubricating properties. MoS2 powder lubricant has better radiation resistance.

    5. Lubrication of conductive sliding surfaces

    The friction of conductive sliding surfaces such as motor brushes, conductive sliders, solar collector rings on sliding satellites working in a vacuum, and sliding electrical contacts can be lubricated with composite materials composed of carbon graphite or metals.

    6. Occasions with very harsh environmental conditions

    In harsh environments, such as transportation machinery, engineering machinery, metallurgy and iron and steel industry institutions, mining machinery and other transmission parts working in harsh environments such as dust, sediment, high temperature and humidity, MoS2 powder lubricant can be used for lubrication.

    7. The occasion of the corrosive environment

    Such as marine machinery, chemical machinery and other transmission parts work in corrosive media such as water (steam), seawater and acids, alkalis, salts, etc., they are subject to different degrees of chemical corrosion. MoS2 powder lubricant can be used as the transmission part in this situation.

    8. When the environmental conditions are immaculate

    MoS2 powder lubricant can be used for transmission parts of electronics, textile, food, medicine, paper making, printing and other machinery to avoid pollution.

    9. Where no maintenance is required

    Some transmission parts do not need support, and some transmission parts need to reduce the number of upkeep to save costs. In these occasions, the use of MoS2 powder lubricant is reasonable and convenient and can save money.


    MoS2 applications

    High-quality MoS2 has higher purity, more regular crystal structure and larger grains. At the same time, the content of non-lubricating solid impurities is lower, which eliminates the negative influence or interference of other contaminants on the molybdenum disulfide lubricant, so that its performance can be fully exerted.

    The application fields of high-purity molybdenum disulfide (≥99%) include semiconductor industry, molybdenum disulfide target, battery industry, carbon brush industry, molybdenum disulfide coating and other areas.

    Infomakis dedicated to the technology development of special oil additives, 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. 

    If you are looking for MoS2 , please feel free to contact us.


    Aug 03
    2020
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