Introduction to fluororubber:
Rubber molecules contain fluorine atoms, and the C-F composed of fluorine atoms and carbon atoms has high performance. At the same time, fluorine atoms have a great adsorption effect, which enhances the C-C bond performance in the fluorocarbon molecular chain and increases with its degree of fluorination. Fluorine atoms can effectively shield the C-C main bond, ensuring the chemical stability of the C-C bond. This special molecular structure makes fluororubber have excellent heat resistance, drug resistance, solvent resistance, fluoride resistance, vacuum resistance, oil resistance, aging resistance and other special properties.
The main types of fluororubber are 26, 246, and 23 types; Tetrapropylene fluororubber, fluorosilicone rubber, hydroxynitroso fluororubber, fluorinated phosphoronitrile rubber, perfluoroether rubber.
The main properties of fluororubber:
1. Chemical stability Fluoroelastomer has a high degree of chemical stability, which is the best medium resistance among all elastomers at present. Type 26 fluororubber is resistant to petroleum based oils, diester oils, and silicone ether silicate oils. It is resistant to inorganic acids and most organic solvents, but not to low molecular weight ketones, ethers, and esters. It is not resistant to hydraulic oils such as amines, ammonia, hydrofluoric acid, chlorosulfonic acid, and phosphoric acid. The 23 type is more unique in that it has better resistance to strong oxidizing inorganic acids such as fuming nitric acid and concentrated sulfuric acid than the 26 type.
2. Excellent high-temperature resistance
The high-temperature resistance of fluororubber, like that of silicone rubber, can be said to be the best among elastomers currently.
3. Good aging resistance
It has excellent weather aging resistance and ozone resistance.
4. Excellent vacuum performance
Has excellent vacuum performance.
5. Excellent mechanical performance
Has excellent physical and mechanical properties. At high temperatures, the compression permanent deformation is large, but under the same conditions, both nitrile rubber and chloroprene rubber are larger than 26 type rubber.
6. Good electrical performance
Type 23 fluororubber has good electrical properties and lower moisture absorption compared to other elastomers, making it a good electrical insulation material. Fluorine rubber is generally only suitable for use under low frequency and low voltage conditions, and temperature has a significant impact on its electrical properties. From 24 ℃ to 184 ℃, its insulation resistance decreases by 35000 times.
7. Hypoxemia
Fluorine rubber has a high solubility in gases, but its diffusion rate is relatively small, so its overall permeability is also low. According to reports, type 26 fluororubber has similar permeability to butyl rubber for oxygen, nitrogen, and carbon dioxide at 30 ℃, and is better than chloroprene rubber and natural rubber.
8. Poor low-temperature performance
Fluorine rubber has poor low-temperature performance due to its inherent chemical structure. For example, the Tg of type 23-11 is greater than 0 ℃. The low-temperature performance of fluororubber used in practice is usually represented by its brittleness temperature and compressive cold resistance coefficient. The formula of the adhesive and the shape of the product have a significant impact on the brittleness temperature.
9. Poor radiation resistance
The radiation resistance of fluororubber is relatively poor among elastomers. Type 26 rubber exhibits crosslinking effect after radiation, while type 23 rubber exhibits cracking effect.
10. As a synthetic rubber, fluororubber has excellent chemical resistance, oil resistance, and temperature resistance, with long-term use temperatures reaching over 200 ° C. Fluorine rubber has high fluorine content, strong C-F bonds, and no unsaturated bonds in its chemical structure, resulting in outstanding temperature resistance and excellent oil resistance. Given that ASTM D1418 refers to fluororubber as FKM, FKM has been used to represent fluororubber. According to the classification of rubber by SAE J200/ASTM D2000, fluororubber is classified as a "HK" material. The initial fluororubber was a copolymer of hexafluoropropylene and vinylidene fluoride, developed by DuPont in 1957 for fuel tank seals, oil and gas seals, and hydraulic system seals in the aerospace industry. Fluorine rubber has been widely used in the industrial field. Used as O-rings, U-rings, V-rings, Y-rings, gaskets, and other forms of static and dynamic seals. And some other components in the fuel and transmission system.
