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1. Introduction Petroleum additives that improve the lubrication performance of lubricants can be divided into two categories in my country: oiliness additives and extreme pressure antiwear agents (EP-Antiwear Agents). Since the distinction between their applicable performance and mechanism of action is not very strict, it is sometimes difficult to distinguish between the two. So in the West * * , extreme pressure agents, anti-wear agents and oily agents are collectively called Load-Carrying additives. In traditional lubrication theory, lubrication is divided into liquid lubrication and boundary lubrication. Two metal surfaces in relative motion are completely separated by a lubricating oil film, and there is no direct contact between the metals. This lubrication state is called liquid lubrication. ； As the load increases, the thickness of the oil film between the metal surfaces gradually becomes thinner. When the load increases to a certain level, the continuous oil film is destroyed by the peaks of the metal surfaces, causing local direct contact between the metal surfaces. This lubrication state is called boundary lubrication. In boundary lubrication, when the metal surface only bears moderate load, if there is an additive that can be adsorbed on the metal surface or wear violently with the metal surface, this additive is called an anti-wear additive. When a metal surface is subjected to a high load, a large number of metal surfaces are in direct contact, generating a large amount of heat, and the film formed by the anti-wear agent is also destroyed and no longer protects the metal surface. If there is an additive that can chemically react with the metal surface to form a chemical reaction film, which acts as a lubrication to prevent the metal surface from being scratched or even welded, this most demanding boundary lubrication is usually called extreme pressure lubrication, and this additive is called an extreme pressure additive. 2. Boundary lubrication mechanism of oil-based agents and the role of adsorption film. When two metal surfaces interact to produce lubricating frictional motion, if they are subjected to large or impact vibration loads, it will not be easy to maintain liquid lubrication and will be in a boundary lubrication state. That is to say, when the oil film thickness is less than 0.0002um, or a complete continuous oil film cannot be maintained, the lubrication performance of the lubricating oil has almost nothing to do with the viscosity, but mainly depends on the "oiliness" of the lubricating oil. That is to say, some of the lubricants (oiling agents) contain polar atoms, such as S, O, N, P, etc., or polar groups, such as -OH, -COOH, -COOR, -COR, -CN, -CHO, -NCS, -NH2, -NHCH3, -NH3, -NROH, -N / R,OH-OR' p // O R2OH-OR" / OH OR' p // O OR" / ONHROH These components with strong affinity and activity to the metal surface and the metal surface molecules rely on van der Waals forces to physically adsorb (the heat of adsorption is about 20KJ/mo1). The polar end of the lowest layer of molecules or a thin layer of several molecules is actually semi-chemically and semi-physically adsorbed to the oxide layer on the metal surface. Such as fatty acid compounds, which form a temporary fatty acid metal soap with the metal surface. For example, stearic acid C17H35COOH undergoes chemical adsorption of electron transfer on the metal surface (the heat of adsorption is more than 40KJ/mo1), forming a monomolecular layer of semi-chemically bonded oily lubricating film, which sometimes also plays an anti-sintering role. The main function of the oily agent is to reduce the friction coefficient and frictional resistance to save power energy. At the same time, it also has the effect of significantly reducing wear under lower load conditions. But this can generally only be used when the load pressure is light and the impact vibration is small, that is, the temperature of the friction part is not higher than 100°C. Generally, metal soap desorbs and loses its oily effect. Extreme pressure agents should be used to solve this problem. 3. Performance and action mechanism of extreme pressure anti-wear agent: When extremely heavy or large impact loads produce local high temperatures approaching 200°C or above, the chemical adsorption film of the oily agent will lose its effect. At this time, extreme pressure agents must be used. The extreme pressure agent initially undergoes an interfacial tribochemical reaction with the solids on the friction metal surface to form a protective lubricating film that prevents contact between the metal friction surfaces. The chemical reaction mechanism of organic polar molecules with a double bond structure, such as α-olefins, is not greatly affected by pressure at this time, but temperature plays a major role. The reaction speed increases by 2 times for every 10°C increase, but it may reach dozens to hundreds of times under the action of friction. As mentioned above, extreme pressure antiwear agents usually include organic chlorides, organic sulfides, organic phosphides, metal salts and others. The function of extreme pressure anti-wear agent is actually a controlled corrosion phenomenon, because only by chemically reacting with the metal friction surface to generate a chemical reaction film with a lower melting point and lower shear strength, can it reduce friction, wear and prevent scratches and welding. The reaction is as follows: 1. Organic chlorides Organic chlorides first decompose under extreme pressure conditions: The C-CL bond breaks, and the decomposition products form a metal chloride film on the metal surface. RCLX+Fe → Fe CL2+RCLX-2 RCLX → RCLX-2+2HCL Fe+2HCL → FeCLX-2+H2 2. The mechanism of action of organic sulfides is first adsorption on the metal surface. Due to the instantaneous temperature of the contact point, the oil film ruptures, and the metal surface and organic sulfides react rapidly to form a load-bearing metal sulfide film. The reaction is as follows: Fe|+RSSR→Fe|< SR SR R-Sx+Fe|→Fe|…S+RSx-1 Fe|+ SR→Fe|< SR SR SR The mechanism by which polar organic sulfides produce anti-wear and extreme pressure resistance on metal surfaces is: RRRR | | | | | | SSSS → S - S +2R→ --|-- --|-- --|-- --|-- -- -|- - --|-- Alkyl, alkenyl, etc. Fe Fe Fe Fe Fe Fe 3. The mechanism of action of organic phosphorus compounds is that under boundary lubrication conditions, the organic phosphorus compounds react with the metal surface to form a metal phosphide-iron low alloy. 4. Organometallic salts and other zinc dialkylthiophosphates (ZDDP) T-202 is an anti-wear agent. When it is thermally decomposed, in addition to releasing hydrogen sulfide, alkanols, sulfides, and disulfides, it also generates a compound composed of O || The polymer film formed by (- P -S-Zn-S- -S-)n OR also has the ability to prevent wear. 4. Variety and performance 1. The varieties of friction modifiers can be roughly divided into two categories: oil-soluble and non-oil-soluble. See the table below for details.: Types of friction modifiers Oil-soluble oily agents containing polar groups Fatty acids, fatty acid esters, organic amine compounds, amide esters, imide compounds, sulfide greases, phosphorus compounds, boric acid esters (salts) Organic metal compounds, organic molybdenum compounds, non-oil-soluble solid lubricants such as molybdenum disulfide (MOS2), graphite, tungsten disulfide (WS2), boron nitride (BN), polytetrachlorethylene (PTFE) and other oil-soluble oil-based lubricants. Most of the non-polar groups are long-chain alkyl groups. The length of the alkyl chain and the position of the polar group are very important factors. The most suitable position for the polar group is at the very end of the alkyl chain, so that the polar end of the long-chain oil agent molecule is vertically adsorbed on the metal surface, which has a greater effect. In addition, the length and type of the alkyl group of the oily agent have different effects when applied to different base oils. 2. Extreme pressure anti-wear agents generally contain organic compounds with active elements such as sulfur, chlorine and phosphorus. Different active elements have different mechanisms of action. Mainly include sulfides, chlorine-containing compounds, phosphorus-containing compounds and organic metal compounds. A. Chlorine-containing additives, such as the typical T-301 additive, generate a protective film of FeCL2 or FeCL3 through chemical adsorption or metal surface reaction on the metal surface, or the reaction of decomposed elemental chlorine and HCL with the metal surface, showing anti-wear and extreme pressure effects. The ferric chloride film has a layered structure, low critical shear strength, and small friction coefficient. However, it has a low heat resistance temperature and ruptures at 300 to 400°C. When it encounters water, it will undergo a hydrolysis reaction to generate hydrochloric acid and ferric hydroxide, which will lose its lubrication effect and cause chemical wear and rust. Therefore, chlorine-containing additives should be used below 350°C and in anhydrous conditions. B. Sulfur-containing extreme pressure anti-wear agents. It is generally believed that the extreme pressure and anti-wear properties of sulfur-containing extreme pressure anti-wear agents are related to the C-S bond properties of sulfides. The weaker C-S bond properties make it easier to form a protective film, resulting in good anti-wear effects, and sulfurized isoolefin T-321 is one of the representative extreme pressure anti-wear agents. Because sulfated isobutylene has a light color, good oil solubility, high sulfur content (40-46%), mostly sulfur-sulfur bond combinations, good extreme pressure and wear resistance, and moderate chemical activity, it is less corrosive to copper, so it is one of the main agent types. C. Phosphate-containing extreme pressure anti-wear agents and phosphides are first adsorbed on the iron surface, and then the C-O bond breaks under boundary conditions to form an organic film of iron phosphite or iron phosphate, which plays an anti-wear role. Under extreme pressure conditions, the organic iron phosphate film further reacts to form an inorganic iron phosphate reaction film, which prevents direct contact between metals, thereby protecting the metal and playing an extreme pressure role. The order of extreme pressure performance of its phosphorus-containing additives can be as follows:: Phosphate amine salt > Phosphate amide ≥ phosphite ≥ acidic phosphate > phosphate > phosphonate > hypophosphite. The worse the thermal stability of the phosphorus series extreme pressure anti-wear additives, the better its anti-wear properties, but the durability of the anti-wear decreases and the additives are consumed faster. Generally speaking, the worse the thermal stability of the phosphide, the better the wear resistance. The most widely used phosphorus-based extreme pressure antiwear agents are alkyl phosphites, phosphate esters, acidic phosphate esters, etc. 5. For the brands of oily agents and extreme pressure anti-wear agents, please refer to the "Kangtai Information" issued internally by Jinzhou Kangtai Lubricant Additive Co., Ltd. The second edition of this issue details the varieties, brands and prices of oily agents (friction modifiers) and extreme pressure anti-wear agents. Users and friends are welcome to purchase and use them. 6. Applications of lubricating oils Depending on the performance of lubricating oils and the severity of usage conditions, gear oils and metal working fluids are the most commonly used extreme pressure anti-wear agents. Gear oils are divided into vehicle gear oils and industrial gear oils. Kangtai Company specially provides various gear oil compounds for the majority of users.: KT-310, KT-320A, T-4201, T-4206 and imported H343, as well as extreme pressure agents RC2317, RC2315, RC2526 imported from Bayer of Germany, etc. 7. Conclusion 1. Correctly select load additives based on friction theory and lubrication performance. This post was last edited by zxh6267 on 2009-3-12 09:42 ]