Special rubber refers to rubber with certain special properties. Mainly: 1 nitrile rubber, referred to as NBR, obtained by copolymerization of butadiene and acrylonitrile. Good oil and aging resistance, long-term use in air at 120 ° C or in oil at 150 ° C. In addition, it has water resistance, air tightness and excellent bonding properties. 2 silicone rubber, the main chain is composed of silicon oxygen atoms alternately, with organic groups on the silicon atom. High temperature resistance, ozone resistance and electrical insulation. 3 fluororubber, a synthetic rubber containing a fluorine atom in its molecular structure. It is usually represented by the number of fluorine atoms of the fluorine-containing unit in the copolymer, such as fluororubber 23, which is a copolymer of vinylidene fluoride and chlorotrifluoroethylene. Fluororubber is resistant to high temperatures, oils and chemicals. 4 polysulfide rubber, which is formed by polycondensation of a dihaloalkane with an alkali metal or alkaline earth metal polysulfide. It has excellent oil and solvent resistance, but its strength is not high, its aging resistance, workability is not good, and it has odor. It is often used together with nitrile rubber. In addition, there are urethane rubber, chlorohydrin rubber, acrylate rubber and the like.