Structural characteristics:
Because there is no unsaturated C=C bond structure on the main chain of polyolefin fluororubber (26-type fluororubber, 23-type fluororubber) and nitroso fluororubber, the possibility of degradation and chain breakage on the main chain due to oxidation and pyrolysis is reduced. The methylene group in vinylidene fluoride plays a very important role in the softness of the polymer chain. For example, fluororubber 23-21 and fluororubber 23-11 are composed of vinylidene fluoride and trifluorochloroethylene in a ratio of 7:3 and 5:5 respectively. Obviously, the former is softer than the latter.
Whether it is vinylidene fluoride and trifluorochloroethylene, or the copolymer of the former and hexafluoropropylene and their terpolymers with tetrafluoroethylene, they can be mainly crystalline or amorphous. This depends on the content of the other monomer when one monomer is the main segment of the copolymer. Electron diffraction studies have shown that when the molar fraction of hexafluoropropylene in the vinylidene fluoride segment reaches 7%, or when the molar fraction of vinylidene fluoride in the trifluorochloroethylene segment reaches 16%, the two copolymers still have the crystal structure of the equivalent homopolymer. However, when the molar fraction of hexafluoropropylene in the former increases to more than 15%, or the molar fraction of vinylidene fluoride in the latter increases to more than 25%, the lattice is greatly destroyed, resulting in an amorphous structure with rubber properties as the main feature. This is because the increase in the amount of the second monomer introduced destroys the regularity of its original molecular chain. Fluororubber can be used in combination with nitrile rubber, acrylic rubber, ethylene-propylene rubber, silicone rubber, fluorosilicone rubber, etc. to reduce costs and improve physical and mechanical properties and process properties.
Historical development:
The earliest fluororubber was poly-2-fluoro-1.3-butadiene and its copolymers with styrene, propylene, etc., which were trial-produced by DuPont in the United States in 1948. Its performance is not more outstanding than that of chloroprene rubber and butadiene rubber, and it is expensive and has no practical industrial value. In the late 1950s, Thiokol Company of the United States developed a binary nitroso fluororubber with good low temperature performance and strong oxidant resistance (N2O4). Fluororubber began to enter practical industrial applications. China has also developed a variety of fluororubbers since 1958. mainly polyolefin fluororubbers, such as type 23. type 26. type 246 and nitroso fluororubbers; subsequently, newer varieties of tetrapropylene fluororubber, perfluoroether rubber, and fluorinated phosphorus rubber were developed. These fluororubber varieties were first based on the needs of supporting national defense and military industries such as aviation and aerospace, and gradually promoted and applied to civilian industrial sectors. They have been applied to cutting-edge technologies such as modern aviation, missiles, rockets, space navigation, ships, atomic energy, and automotive, shipbuilding, chemical, petroleum, telecommunications, instruments, machinery and other industrial fields.
Application fields:
Fluororubber is widely used in daily life, such as in automotive parts, aviation and aerospace fields, mechanical seals, pumps, reactors, agitators, compressor housings, valves, various instruments and other equipment as valve seats, valve stem fillers, diaphragms and gaskets, as well as in the rubber sheet industry, semiconductor manufacturing industry and food and pharmaceutical industries.
With the use of unleaded gasoline and electronic injection devices in automobiles, the structure and materials of fuel hoses have changed greatly. Fluororubber has replaced nitrile rubber with the inner rubber layer. In order to reduce fuel penetration and further improve heat resistance, the inner rubber layer mostly adopts a composite structure, that is, composed of fluororubber and chlorohydrin rubber or acrylate rubber. Since fluororubber is relatively expensive, the fluororubber layer is relatively thin, with a thickness of about 0.2 to 0.7 mm. This type of fuel hose has become a mainstream product abroad. my country has also developed this type of hose with fluororubber as the inner layer, and it is used on cars such as Santana, Audi, Jetta, and Fukang. In the technically advanced automotive engine, gearbox, and valve oil seals, the materials used are mainly fluororubber, hydrogenated nitrile rubber, etc.
Fluororubber and silicone rubber composite oil seals have become the most commonly used engine crankshaft oil seals. The hydraulic system of loading and unloading trucks and the hydraulic system of large loading and unloading trucks work continuously for a long time, and the oil temperature and the temperature of the parts rise very quickly. Ordinary rubber cannot meet their working requirements, while fluororubber products can meet various demanding technical requirements with their excellent temperature resistance. With the continuous improvement of the automotive industry's requirements for reliability and safety, the demand for fluororubber in the automotive industry has also shown a rapid growth trend.
In addition to automotive industry applications, fluororubber seals are used in drilling machinery, oil refining equipment, natural gas, and power plant desulfurization equipment. They can withstand harsh conditions such as high temperature, high pressure, oil, and highly corrosive media at the same time; in chemical production, fluororubber seals are used in pumps and equipment containers to seal inorganic acids, organic matter and other chemical substances. In the petroleum and chemical industries, fluororubber sealing products are used in mechanical seals, pumps, reactors, agitators, compressor housings, valves, various instruments and other equipment, such as valve seats, valve stem packing, diaphragms and gaskets. Fluororubber is one of the indispensable high-performance materials for cutting-edge science and technology such as modern aviation, missiles, rockets, space navigation, ships, and atomic energy. In recent years, new fluororubber products have been continuously developed in the fields of aviation and aerospace.
