What synthetic rubber is commonly used to make auxiliary sealing rings of mechanical seals and what are their characteristics

Rubber is a polymer material with good elasticity. It has good elasticity and certain strength, and has good air tightness, water impermeability, wear resistance, temperature resistance, pressure resistance, and corrosion resistance. It is a widely used auxiliary sealing ring material in making mechanical seals.

Rubber is divided into natural rubber and synthetic rubber. Natural rubber is superior to synthetic rubber in terms of elasticity, strength, processing performance and comprehensive performance, but it is not as good as synthetic rubber in terms of temperature resistance, corrosion resistance, and dissolution resistance. Synthetic rubbers with different characteristics can be obtained by adopting different rubber varieties, formulations, mixing and vulcanization processes to make sealing rings of mechanical seals.

1)Nitrile rubber (NBR) Nitrile rubber is a copolymer of butadiene and acrylonitrile. Commonly used nitrile rubber with a propanonitrile content of 40% has good oil resistance and aging resistance, and has heat resistance, wear resistance and corrosion resistance, and is widely used in equipment contacting gasoline and other oils. It is also resistant to alkali and non-oxidizing dilute acids, but not to oxidizing acids (such as nitric acid and chromic acid, etc.), aromatic hydrocarbons, esters, ketones, ethers, halogenated hydrocarbons, etc. Because the condensed oil in the refinery contains aromatics and other media, nitrile rubber cannot be used in this case. It should not be used at low temperature also.

2)Silicone rubber (MVQ) Silicone rubber is a kind of linear polymer elastomer polymerized by dimethyl siloxane and other silicone monomers under the acidic (or basic) catalyst. Silicone rubber has a wide temperature range (-100~350°C) and high thermal stability, and can generally be used for a long time at 200~300°C. It is mainly used for sealing animal and vegetable oils, mineral oils, oxygen, weak acids and weak bases at high and low temperatures. Its disadvantages are low strength, non-wear resistance and high price.

3) Fluorine rubber (FPM) Fluorine rubber is a synthetic polymer elastomer containing fluorine atoms, which has the characteristics of high temperature resistance, oil resistance and corrosion resistance of various chemicals. At present, there are three varieties of fluororubber: FPM2301, fluororubber 23-11, which has excellent strong acid resistance; FPM2602, fluororubber 26-41, has better heat resistance and solvent resistance than FPM2301, but has poor process performance; FPM with 2461, that is, fluorine rubber 246, its heat resistance and solvent resistance are better than FPM2602. At present, the fluorine rubber used in the manufacture of auxiliary sealing rings of mechanical seals is mainly FPM2602.It can be used for a long time at 250°C and can be used for a short time at 300°C. Its corrosion resistance is the best among elastomers, but its low temperature performance is poor and its price is expensive, which limits its scope of use.

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