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What Are The Commonly Used Materials For Mechanical Seals?
May 15, 2018

What are the commonly used materials for mechanical seals?

Suction pump mechanical seal commonly used materials

The commonly used materials for the mechanical seals of the oil pump are nitrile rubber, fluorine rubber, silicon rubber, and neoprene rubber.

Nitrile rubber (NBR) is a commonly used electric pump oil resistant rubber. Its mechanical seal is a copolymer of dibutylene and acrylonitrile. According to the content of acrylonitrile into the following: low acrylonitrile (butyronitrile-18), medium acrylonitrile (NBR-26) and high acrylonitrile (nitrile 40). The higher the acrylonitrile content, the better its oil resistance, tensile strength, hardness and abrasion resistance, water resistance, and air permeability. As a result, its solubility in polar solvents increases, corrosion resistance also suffers, and elasticity and cold resistance also deteriorate. Nitrile rubber is not resistant to flexion and tear resistance is also poor.

The acrylonitrile content of the commonly used nitrile rubber seals is 26% to 50%.

Fluorine rubber (FPM) has the advantages of high temperature resistance, oil resistance, and chemical resistance. The most widely used mechanical seals for fluorine rubber in domestic oil pumps are fluorine-containing olefin copolymers, mainly type 26 and type 23. The 26-type fluororubber-26-series vinylidene fluoride and hexafluoropropylene to emulsion copolymer and fluorine rubber-246 series vinylidene fluoride, hexafluoropropylene tetrafluoroethylene terpolymer. The 23-type fluororubber is an amorphous rubber-like copolymer obtained by suspension polymerization of vinylidene fluoride and chlorotrifluoroethylene at ordinary temperature and a pressure of about 3.24 mpa. It cannot be used for liquid ammonia, ammonia, etc.

In recent years, the maximum operating temperature of fluororubber is 250°C, and use at high temperatures is limited to develop perfluororubber kalrez (FFKM perfluoropolymer elastomer). Its anti-aging properties are good, there is no star aging phenomenon after using at 260°C for 112 days. Tensile strength is still about 90% of the original, can be used continuously at 288 °C, 310 °C short-term use. Its oil resistance, abrasion resistance and corrosion resistance to mixed organic matter are good, but its expansion coefficient is close to twice that of NBR (320x10-61K) and it is not suitable for use below 0°C.

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