Rubber is a very good elastic polymer material.With good elasticity and a certain strength, with good air tightness, impermeability, wear resistance, temperature and pressure resistance, corrosion resistance, is a widely used auxiliary sealing ring material.Rubber is divided into natural rubber and synthetic rubber.Natural rubber is better than synthetic rubber in elasticity, strength, processing performance and comprehensive performance, but it is not as good as synthetic rubber in temperature resistance, corrosion resistance and dissolution resistance.Synthetic rubber with different characteristics can be obtained by adopting different rubber variety formula, mixing and vulcanization process.

　　Nitrile rubber.

　　Nitrile rubber is a copolymer of butadiene and acrylonitrile.Commonly used nitrile rubber content is 40% acrylonitrile, oil resistance, aging resistance performance is good, and has heat resistance and wear resistance and corrosion resistance performance, widely used in contact with gasoline and other oil equipment.It can also be resistant to alkali and non-oxidative dilute acid corrosion, but it is not resistant to the corrosion of oxidative acids (such as nitric acid and chromic acid, etc.), aromatic hydrocarbons, esters, ketones, ethers, halogenated hydrocarbons, etc.Because the refinery condensate contains aromatic hydrocarbons and other media, so nitrile rubber can not be used in this situation. It should not be used at low temperature.

　　Silicone rubber.

　　Silicone rubber is a linear polymer elastomer composed of dimethylsiloxane and other silicone monomers under acidic (or alkaline) catalyst.Silicone rubber has a very wide service temperature range (-100~350℃) and a very high thermal stability, generally can be used for a long time at 200~300℃.Mainly used for high and low temperature animal and plant oil, mineral oil, oxygen, weak acid and weak alkali and other substances sealing. Its disadvantages are low strength, not wear-resistance, high price.

　　Fluorine rubber.

　　Fluorine rubber is a kind of synthetic polymer elastomer containing fluorine atoms, which has the characteristics of high temperature resistance, oil resistance and a variety of chemical corrosion resistance.

　　At present, there are three varieties of fluorine rubber: FPM2301, namely fluorine rubber 23-11, with excellent acid resistance; FPM2602, namely fluorine rubber 26-41, heat resistance and solvent resistance is better than FPM2301, but the process performance is poor: FPM2461, namely fluorine rubber 246, its heat resistance and solvent resistance is better than FPM2602.

　　At present, the fluorine rubber used to manufacture the auxiliary sealing ring is mainly FPM2602. It can be used for a long time at 250℃, and can be used for a short time at 300℃. Its corrosion resistance is the best one of the elastomers, but its low temperature performance is poor and the price is expensive, which limits its use range.