Commonly used additives for lithium grease

2020-05-15 14:59:58 Shenzhen Hecheng 0


The additives commonly used in lithium-based greases are similar to other greases, but the additives used in lithium-based greases are more extensive, and it has good compatibility with many additives. Commonly used additives are mainly antioxidants, metal surface passivating agents, preservatives, structural modifiers, extreme pressure antiwear agents, color stabilizers, and stringiness enhancers.

    1. Antioxidant

    Commonly used antioxidants for lithium-based greases are:

    (1) Diphenylamine has a molecular weight of 169.2, which is a commonly used antioxidant additive for lithium-based greases. The pure product is white mono-oblique needle crystals, and the industrial products are crystals from yellow to brown. The melting point is 52.9°C and the boiling point is 302°C. Insoluble in water, soluble in organic solvents such as alcohol, ether and benzene. Industrial products can be refined with ethanol, and gradually change color when they are exposed to light. Tests have shown that the antioxidant effect of diphenylamine in mineral oil lithium-based grease is better than phenyl-α-naphthylamine. The optimal dosage is 0.1%~1.0%.

    (2) Benzy-α-naphthylamine Also known as anti-aging agent A, the unified code for petroleum additives is T531. Colorless flaky crystals, which gradually turn yellow or purple when exposed to sunlight or air. poisonous! Relative density 1.16~1.17, melting point 62℃. Insoluble in water, soluble in organic solvents such as ethanol, ether, benzene, etc. It is mainly used as an antioxidant for rubber products and one of the most effective oxidation inhibitors for grease. It is commonly used in synthetic ester oils and other lithium-based greases, and the use temperature can reach 150 ℃. The added amount is generally 0.1%~1.0%.

    (3) Phenyl-β-naphthylamine Also known as anti-aging agent D. The pure product is light gray needle-like crystals, which gradually turn to gray-red when exposed to air or sunlight. Relative density 1.18~1.19, melting point 106~108℃. It is insoluble in water, soluble in ethanol and carbon tetrachloride, and easily soluble in organic solvents such as acetone, ethyl acetate, methyl chloride, benzene and carbon disulfide. Its properties are basically the same as phenyl-α-naphthylamine, and it is an important general anti-aging agent.

    (4) 2,6-di-tert-butyl-p-cresol The unified code for petroleum additives is T501. The pure product is white crystal, which becomes yellow and gradually darkens when exposed to light. Relative density 1.048, melting point 70℃, boiling point 257~265℃. Insoluble in water and dilute alkaline solution, soluble in benzene, toluene, alcohol, ketone, carbon tetrachloride, ethyl acetate and gasoline. The low-temperature antioxidant effect of this antioxidant is better. If this antioxidant is used in combination with other antioxidants, such as diisooctyldiphenylamine, its antioxidant effect will be increased several times.

    Antioxidant in the order of anti-oxidation effect in 12-hydroxystearic acid lithium base grease: diphenylamine> benzyl-α-naphthylamine> zinc dipentyldithiocarbamate.

    2. Rust inhibitor

    Commonly used lithium-based grease rust inhibitors are:

    T701 barium petroleum sulfonate, T704 zinc naphthenate, T705 dinonylnaphthalene barium petroleum sulfonate, T706 benzotriazole.

    T701, T704, and T705 all have good effects on copper rust, and the derivative of benzotriazole octadecylamine also has good effects on rust.

    3. Extreme pressure and anti-wear additives

    Due to the development of modern technology, the lubrication of many equipments in the steel industry and heavy machinery industry is in the state of boundary lubrication. The lubrication of mechanical working parts requires the use of high-quality extreme pressure grease to meet the lubrication requirements. Lithium-based grease is a general-purpose grease. It has good compatibility with extreme pressure and anti-wear additives. After adding extreme-pressure anti-wear additives, extreme-pressure lithium-based grease can be prepared.

    The effect of using extreme pressure additives generally follows this pattern. Phosphorus compounds can effectively improve the wear resistance of greases, while sulfur and chlorine compounds can effectively improve the load resistance of greases. Sulfur-containing compounds are better than chloride-containing compounds. At the same time, compounds containing chlorine and phosphorus or phosphorus And sulfur compounds, both extreme pressure and abrasion resistance. In order to improve the wear resistance and extreme pressure of the lubrication batch, two or more extreme pressure antiwear additives can be used in combination.

    4. Wire drawing agent of adhesive (structure improver)

    In recent years, many special lithium-based greases have added ethylene-propylene copolymers, polyacrylates, polyisobutylene and other high polymers to improve the mechanical stability of the grease and increase the adhesion and stringiness of the grease.

    5. Filler (filler)

    Fillers often refer to finely dispersed solid substances, which also have the characteristics of solid lubricants. The purpose of adding fillers is to reinforce the lubricating film of the basic grease under heavy load, vibration, impact load or high temperature. There are many types of fillers, and currently used in lithium-based greases are mainly molybdenum disulfide, graphite, boron nitride, MCA (melamine cyanurate), PTFE (polytetrafluoroethylene), etc.


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