1. What is fluorosilicone?
Fluorosilicone is a new type of elastomer that combines the advantages of silicone rubber and fluorine rubber. Silicone rubber represented by dimethylpolysiloxane has excellent high-low temperature properties, electrical properties and elastic properties, but this rubber has poor saturated steam resistance, oil resistance and solvent resistance, making its application It has been greatly restricted: after introducing fluorine-containing groups (such as trifluoropropyl) into the carbon chain of silicone rubber to form fluorosilicone rubber, due to the great electron-withdrawing effect of fluorine atoms, plus the bond of C-F bond The short length can form a better shielding effect on C-C bonds, which greatly improves the oil resistance and solvent resistance of rubber. Therefore, fluorosilicone rubber maintains the heat resistance, cold resistance, compression recovery, resilience, and electrical properties of silicone rubber. It not only has a series of excellent properties such as properties and mold release properties, but also has the oil resistance and solvent resistance of fluororubber. It can be called the "oil fighter" among silicone elastomers.
2. Performance characteristics of fluorosilicone
1. Oil, solvent and chemical resistance
Compared with methylvinyl silicone rubber, fluorosilicone rubber has extremely excellent oil resistance, solvent resistance, and chemical resistance; even compared with fluororubber, its oil resistance and solvent resistance are also good. It shows excellent durability after immersion in the same medium, temperature and time. It can be said that fluorosilicone rubber is the only elastomer that can withstand non-polar media at -68°C ~ 232°C.
Fluorosilicone rubber also has relatively good resistance to methanol-containing gasoline. Even in a gasoline/methanol (85vol%/15vol%) mixed system, the hardness, tensile strength, and volume of the vulcanized rubber change very little. After 500 hours of use, the After the immersion test, there was almost no change in various physical properties.
2. Heat resistance
The high temperature decomposition of fluorosilicone rubber is the same as that of silicone rubber, namely: side chain oxidation, main chain breakage, side chain thermal decomposition and various composite reactions. Since the decomposition products can also cause the main chain to break, the heat resistance is usually worse than that of silicone rubber, and it has begun to oxidize and age at a temperature of 200°C. However, by adding a small amount of heat stabilizers such as iron, titanium, rare earth oxides, etc., it can be significantly improved, and it has sufficient heat resistance even at a high temperature of 250°C.
The effect of temperature on fluorosilicone rubber is greater than that of silicone rubber, but less than that of fluororubber. Foreign studies have also studied the service life of fluorosilicone rubber under the conditions of 150℃×2000h, 175℃×5000h, and 200℃×4000h. The results are second only to methyl vinyl silicone rubber.
3. Cold resistance
Fluorosilicone rubber, like ordinary silicone rubber, has good low-temperature properties. Since fluorosilicone rubber is a linear polymer composed of soft Si-O as the main chain, its low temperature characteristics are better than those of fluororubber with C-C as the main chain. Among them, fluorosilicone has better low-temperature characteristics, with a brittleness temperature as low as -89°C, while general fluororubber is about -30°C.
4. Electrical properties and radiation resistance
The electrical properties of fluorosilicone rubber are similar to ordinary silicone rubber, but what is particularly valuable is that it changes very little under harsh conditions such as high temperature, low temperature, moisture, oil, solvents, chemicals, and ozone.
The radiation resistance of fluorosilicone rubber is not outstanding, but its radiation aging resistance is better than that of methyl vinyl silicone rubber.
5. Physical and mechanical properties
Fluorosilicone rubber is the same as ordinary silicone rubber. The mechanical strength of vulcanized rubber (especially tear strength) is relatively low. Therefore, improving and increasing the strength of fluorosilicone rubber is also an important research topic.
6. Other features
Fluorosilicone rubber has excellent weather aging resistance and still maintains good performance even after 5 years of exposure. Ozone is one of the most generated gases when elastomers age, but no cracks or cracks were found in fluorosilicone rubber after passing dynamic or static tests.
3. Main uses of fluorosilicone rubber:
Fluorosilicone rubber is generally used to prepare fuel- and solvent-resistant seals, sealing rings, oil seals, diaphragms, conduits, valve liners, hoses, integral fuel tank seals, O-rings and Gaskets, and used for surface coating of connecting parts in the power and electronic industries and cables, conveyor belts, fabrics, etc. It is an important rubber material in the defense industry and aerospace fields.
Fluorosilicone processing and production precautions and suggestions
Because fluorosilicone rubber is expensive, and on the other hand, due to characteristics such as the electron-attracting effect of fluorosilicone rubber, it has a strong adsorption effect on surrounding dust, thus affecting performance, so the production and operation process of fluorosilicone rubber is extremely strict. The following part of the production process control is briefly shared.
1. Transportation and storage of fluorosilicone rubber: During the storage and transportation of fluorosilicone rubber, the fluorosilicone rubber must be wrapped in isolation paper and plastic bags to prevent dust and impurities from coming into contact with the rubber and being absorbed.
2. Cutting of fluorosilicone rubber: In the process of collecting and cutting fluorosilicone rubber, you must first clean the scissors or putty knife used, use alcohol to scrub the surface of the tool, and then cut the fluorosilicone after it is clean. Rubber, during the cutting process, try to avoid contact between hands, skin and rubber, but do not wear gloves to avoid contamination of fluorosilicone rubber by glove fibers or skin oils.
3. Mixing and vulcanization: Before mixing, the rollers and baffles of the open mill must be wiped with alcohol to ensure that there is no impurity contamination. When mixing, attention should be paid to controlling the roller temperature. When the roller temperature is 18℃~28℃, the rubber mixing process performance is better. For the use of rubber materials that have been parked for a long time, re-refining is required to ensure that the materials are evenly mixed. The vulcanization mold must be surface chrome plated. Fluorosilicone rubber needs to be vulcanized in the second stage in an electric blast box, usually at: 200°C × 4 to 6 hours.
4. Fluorosilicone production environment: Since fluorosilicone has the characteristics of electrostatic dust absorption, the production environment needs to be purified and dust-free workshop, and the production tools are special equipment. Workers must wear clean clothes and hats when entering and exiting operations.
Low pressure variable fluorosilicone compound
