Performance and uses of fluorine rubber
1. Introduction to fluorine rubber:
Rubber molecules contain fluorine atoms. The C-F properties composed of fluorine atoms and carbon atoms are very high. At the same time, fluorine atoms have a great adsorption effect, which enhances the performance of the C-C bonds in the fluorocarbon molecular chain and increases with the increase in the degree of fluorination. Enhanced, fluorine atoms can better shield the C-C primary bond to ensure the chemical inertness of the C-C bond. This special molecular structure makes fluorine rubber have excellent heat resistance, chemical resistance, solvent resistance, fluorination resistance, vacuum resistance, oil resistance, aging resistance and other specific properties.
The main types of fluororubber are type 26, type 246, and type 23; tetrapropylene fluororubber, fluorosilicone rubber, hydroxynitroso fluororubber, fluorinated phosphazene rubber, and perfluoroether rubber.
2. Main properties of fluorine rubber
1. Chemical stability Fluorine rubber has a high degree of chemical stability and has the best media resistance among all elastomers currently. Type 26 fluorine rubber is resistant to petroleum-based oils, diester oils, silicone silicic acid oils, inorganic acids, and most organic solvents, but is not resistant to low-molecular ketones, ethers, esters, amines, ammonia, Hydrofluoric acid, chlorosulfonic acid, phosphoric acid hydraulic oil. Type 23 is even more unique. Its resistance to strong oxidizing inorganic acids such as fuming nitric acid and concentrated sulfuric acid is better than Type 26.
2. Excellent high temperature resistance
The high temperature resistance of fluorine rubber is the same as that of silicone rubber, and it can be said to be the best among current elastomers. 246＞26＞23
3. Good aging resistance
It has excellent weather aging resistance and ozone resistance.
4. Excellent vacuum performance
Has excellent vacuum performance.
5. Excellent mechanical properties
Has excellent physical and mechanical properties. The compression permanent deformation at high temperature is large, but if compared under the same conditions, nitrile rubber and chloroprene rubber are larger than type 26 rubber.
6. Good electrical performance
Type 23 fluororubber has better electrical properties and lower hygroscopicity than other elastomers, so it can be used as a better electrical insulation material. Fluorine rubber is generally only suitable for use under low frequency and low voltage. Temperature has a great impact on its electrical properties. When it rises from 24°C to 184°C, its insulation resistance drops by 35,000 times.
7. Small temper
Fluorine rubber has high gas solubility, but its diffusion rate is relatively small, so its overall breathability is also small. According to reports, the breathability of type 26 fluororubber to oxygen, nitrogen, and carbon dioxide at 30°C is equivalent to that of butyl rubber, and better than chloroprene rubber and natural rubber.
8. Poor low temperature performance
Fluorine rubber has poor low-temperature performance, which is due to its own chemical structure. For example, the Tg of type 23-11 is >0℃. The low-temperature properties of fluororubber actually used are usually expressed by brittle temperature and compression cold resistance coefficient. The formula of the rubber compound and the shape of the product have a greater impact on the brittleness temperature.
9. Poor radiation resistance
The radiation resistance of fluorine rubber is relatively poor among elastomers. Type 26 rubber shows a cross-linking effect after radiation, and type 23 shows a cracking effect.
10. As a kind of synthetic rubber, fluororubber has excellent chemical resistance, oil resistance and temperature resistance, and its long-term use temperature can reach above 200°C. The chemical structure of fluorine rubber has the characteristics of high fluorine content, strong C-F bonds, and no unsaturated bonds, so it has outstanding temperature resistance and excellent oil resistance. Since fluorine rubber is called FKM in ASTM D1418, FKM is used to represent fluorine rubber. According to the SAE J200/ASTM D2000 classification of rubber, fluorine rubber is classified as a "HK" material. The original fluororubber is a copolymer of hexafluoropropylene and vinylidene fluoride. It was developed by DuPont in the United States in 1957 and used for fuel tank seals, oil and gas seals and hydraulic system seals in the aerospace field. Fluorine rubber has been widely used in industrial fields. Used as O-rings, U-rings, V-rings, Y-rings, gaskets and other forms of static and dynamic seals. as well as some other components in the fuel and transmission systems.