Fluorine rubber refers to a type of synthetic polymer elastomer that contains fluorine atoms in the carbon atoms of the main chain or side chain and can be vulcanized. This kind of elastomer has many excellent properties due to its own composition and structural characteristics, so it is an excellent elastic engineering material. It is widely used in key parts of industries such as aviation, automobile, shipbuilding, machinery, chemical industry, and light industry.
Characteristics: high heat resistance, excellent chemical inertness, good physical and mechanical properties (including wear resistance), outstanding stability to the atmosphere, satisfactory dielectric properties and non-combustibility, it is currently used elastomer One of the most heat-resistant and chemical-resistant. It has the special properties of PTFE due to poor mechanical sealing and general rubber's inability to resist corrosion.
Varieties: Viton 26B, G, Viton 246G, B, Viton TP, various specifications of skeleton oil seals, "O" rings and other seals.
Fluorine rubber has the characteristics of high temperature resistance, oil resistance and corrosion resistance of a variety of chemicals. It is an indispensable material for modern aviation, missiles, rockets, space navigation and other cutting-edge science and technology. In recent years, with the continuous improvement of the automotive industry's requirements for reliability and safety, the amount of fluorine rubber in automobiles has also increased rapidly. Fluororubber (fluororubber) refers to a synthetic polymer elastomer containing fluorine atoms on the carbon atoms of the main chain or side chain. The earliest fluorine rubber was poly-2-fluoro-1.3-butadiene and its copolymers with styrene, propylene, etc., trial-produced by DuPont in the United States in 1948, but its performance is not more outstanding than that of neoprene and butadiene rubber. It is expensive and has no real industrial value.
Fluorine rubber has the characteristics of high temperature resistance, oil resistance and corrosion resistance of a variety of chemicals. It is an indispensable material for modern aviation, missiles, rockets, space navigation and other cutting-edge science and technology. In recent years, with the continuous improvement of the automotive industry's requirements for reliability and safety, the amount of fluorine rubber in automobiles has also increased rapidly.
Fluororubber (fluororubber) refers to a synthetic polymer elastomer containing fluorine atoms on the carbon atoms of the main chain or side chain. The earliest fluororubber was poly-2-fluoro-1.3-butadiene and its copolymers with styrene, propylene, etc., trial-produced by DuPont in the United States in 1948, but its performance was not more outstanding than that of neoprene and butadiene rubber. It is expensive and has no real industrial value. In the late 1950s, American Thiokol Company developed a binary nitroso fluororubber with good low temperature performance and strong oxidant resistance (N2O4), and fluororubber began to enter practical industrial applications. Since then, with technological progress, various new types of fluoroelastomers have been continuously developed.
Since 1958, China has also developed a variety of fluororubbers, mainly polyolefin fluororubbers, such as type 23, 26, 246 and nitroso fluororubbers; later, they developed newer varieties of tetrapropylene fluororubber , Perfluoroether rubber, fluorinated phosphorous rubber. These fluororubber varieties are first based on the needs of aviation, aerospace and other national defense and military industries, and gradually promoted and applied to the civilian industry.
Main performance
Good chemical stability
Fluorine rubber has a high degree of chemical stability and is the best medium resistance among all elastomers. Type 26 fluororubber is resistant to petroleum-based oils, diester oils, silicone ether oils, and silicic acid oils. It is resistant to inorganic acids, most organic and inorganic solvents, chemicals, etc., but not resistant to low-molecular ketones, ethers, etc. Ester, not resistant to amine, ammonia, hydrofluoric acid, chlorosulfonic acid, phosphoric acid hydraulic oil. The medium performance of type 23 fluorine rubber is similar to that of type 26, and it is more unique. It has better resistance to strong oxidizing inorganic acids such as fuming nitric acid and concentrated sulfuric acid than type 26. It is impregnated in 98% HNO3 at room temperature. 27 Its volume expansion is only 13%~15%.
Excellent high temperature resistance
The high temperature resistance of fluorine rubber is the same as that of silicone rubber, which can be said to be the best among elastomers. 26-41 fluorine rubber can be used for a long time at 250°C and short-term use at 300°C; 246 fluorine rubber has better heat resistance than 26-41. The physical properties of 26-41 after air heat aging at 300℃×100 hours are equivalent to those of type 246 after air aging at 300℃×100 hours. The elongation at break can be maintained at about 100%, and the hardness is 90 to 95 degrees. . Type 246 maintains good elasticity after aging in hot air at 350°C for 16 hours, and maintains good elasticity after aging in hot air at 400°C for 110 minutes. After aging in hot air at 400°C for 110 minutes, it contains spray carbon black, thermal black or carbon fiber. The elongation of the rubber compound increases by about 1/2~1/3, and the strength decreases by about 1/2, still maintaining good elasticity. The 23-11 type fluorine rubber can be used for a long time at 200°C and for a short time at 250°C.
Good aging resistance
Fluorine rubber has excellent weather resistance and ozone resistance. According to reports, the performance of VitonA developed by DuPont is still satisfactory after ten years of natural storage, and there is no obvious cracking after 45 days of action in the air with an ozone concentration of 0.01%. Type 23 fluororubber has excellent weathering resistance and ozone resistance.
Excellent vacuum performance
Type 26 fluorine rubber has excellent vacuum performance. The vacuum outgassing rate of the vulcanized rubber of the basic formula of 246 fluorine rubber is only 37×10-6 Torr/sec. Cm 2. 246 fluoroelastomer has been successfully applied under vacuum conditions of 10-9 Torr.
Excellent mechanical properties
Fluorine rubber has excellent physical and mechanical properties. Type 26 fluororubber generally has a combined strength of 10-20 MPa, a breaking elongation of 150-350%, and a tearing strength of 3-4KN/m. The strength of Type 23 fluororubber is between 15.0 and 25MPa, the elongation is between 200% and 600%, and the tear resistance is between 2 and 7MPa. Generally, the compression set of fluorine rubber at high temperature is large, but if compared under the same conditions, such as the compression set of the same time at 150℃, both butyl and neoprene are larger than type 26 fluorine rubber. The compression set of Type 26 fluororubber at 200°C×24 hours is equivalent to that of butadiene rubber at 150°C×24 hours.
Better electrical performance
Type 23 fluororubber has better electrical properties and lower moisture absorption than other elastomers, so it can be used as a better electrical insulating material. Type 26 rubber can be used under low frequency and low pressure.
Low air permeability
Fluorine rubber has a relatively large solubility to gas, but its diffusion rate is relatively small, so the overall performance of the gas permeability is also small. According to reports, the permeability of 26-type fluororubber to oxygen, nitrogen, helium, and carbon dioxide gas at 30°C is equivalent to that of butyl rubber and butadiene rubber, and better than neoprene and natural rubber.
Low temperature performance is not good
The low temperature performance of fluorine rubber is not good, which is due to its own chemical structure, such as 23-11 type Tg>0℃. The actual low temperature performance of fluorine rubber is usually expressed by brittle temperature and compression cold resistance coefficient. The formula of the rubber compound and the shape of the product (such as thickness) have a relatively large influence on the brittleness temperature. If the amount of filler in the formula increases, the brittleness temperature will be sensitively deteriorated, and the thickness of the product will increase, and the degree of brittleness will also be sensitively deteriorated.
Poor radiation resistance
The radiation resistance of fluororubber is one of the poorer elastomers. Type 26 rubber exhibits cross-linking effect after radiation, and type 23 fluororubber exhibits cracking effect. The performance of Type 246 fluororubber under normal temperature radiation in the air changes drastically at a dose of 5 x 107 luns. Under the condition of 1 x 107 lons, the hardness increases by 1 to 3 degrees, the strength decreases by less than 20%, and the elongation decreases by 30% to 50%. Therefore, it is generally believed that Type 246 fluoroelastomer can withstand 1×107 lons, and the limit is 5×107 lons.
Key Application
Because fluoroelastomer has the characteristics of high temperature resistance, oil resistance, high vacuum resistance, acid and alkali resistance, and a variety of chemical resistance, it has been used in modern aviation, missiles, rockets, astronautics, ships, atomic energy and other cutting-edge technologies, as well as automobiles, shipbuilding, chemistry, Petroleum, telecommunications, instrumentation, machinery and other industrial fields.
Typical application
Fluorine rubber seals, when used for engine sealing, can work for a long time at 200 ℃ ~ 250 ℃, and work for a short time under 300 parallel. Its working life can be the same as the engine repair life, reaching 1000 to 5000 flight hours (time 5~ 10 years); when used in the chemical industry, it can seal mineral acids (such as 67% sulfuric acid at 140 ℃, concentrated hydrochloric acid at 70 ℃, and 30% nitric acid at ℃), organic solvents (such as chlorinated hydrocarbons, benzene, High aromatic gasoline) and other organic substances (such as butadiene, styrene, propylene, phenol, fatty acids at 275°C, etc.); when used in deep well oil production, it can withstand harsh working conditions of 149°C and 420 atmospheres; used for overheating When the steam seal is used, it can work for a long time in the steam medium of 160~170℃. In the production of monocrystalline silicon, fluorine rubber seals are commonly used to seal special media at high temperatures (300°C)-trichlorosilane, silicon tetrachloride, gallium arsenide, phosphorus trichloride, trichloroethylene, and 120°C The hydrochloric acid and so on.
In terms of high vacuum applications, when the flying altitude is 200~300Km, the air pressure is 133×10-6 Pa (10-6mmHg), neoprene, butadiene rubber, butyl rubber can be used; when the flying altitude exceeds 643Km, The air pressure will drop below 133×10-7Pa (10-7mmHg), and only fluorine rubber can be used in this high vacuum. Generally, the high-vacuum or ultra-high-vacuum device system needs to be baked at high temperature before being used. Model 26 and 246 fluoroelastomers can withstand high temperature aging at 200℃~250℃, so they become the most important rubber in high vacuum equipment and spacecraft. Material.
The hose made of fluorine rubber is suitable for high temperature resistance, oil resistance and special medium resistance, such as aircraft fuel oil, hydraulic oil, synthetic diester oil, high temperature hot air, thermal inorganic and other special media (such as chlorinated hydrocarbons and Other chlorides) transportation, guidance, etc. Wires and cables made of fluorine rubber have good flexibility and good insulation. The glass fiber tape made of fluorine rubber can withstand high temperature of 300℃ and resist chemical corrosion. After the aramid cloth is coated with fluorine rubber, it can be used to make the connection expansion pipe between the high temperature resistant, acid and alkali resistant storage tanks of the petrochemical plant (the two ends can be connected by metal flanges), which can withstand high pressure, high temperature and medium corrosion. The deformation and expansion of the two tanks play the role of cushioning and shock-absorbing connection. The rubber-cloth sealed bag made of nylon cloth coated with fluorine rubber is used as a soft seal for the inner floating roof storage tank of an oil refinery to seal and reduce the volatilization loss of the oil level.