You may have heard of Fluorosilicone Rubber, but you don’t necessarily know much about it. When you are shopping for silicone products, you may not know how to choose when facing so many types of silicone rubber. In this article, we will provide a full introduction for you, and we hope that it will help you in your purchase.
Composition Of Fluorosilicone Rubber
Fluorosilicone Rubber is actually a silicone rubber system material containing fluorine, which is a base-modified high-performance elastomer. So, do you know what the characteristics of ordinary silicone rubber are? The main chain of silicone rubber is the silicone-oxygen main chain. It is structurally stable, temperature-resistant, and elastic. Fluorosilicone Rubber has more fluorine-containing side chains than ordinary silicone rubber.
This side chain does not change the basic properties of silicone rubber. It does, however, help silicone rubber reduce its affinity for oils and fuels. This makes it harder for oils to penetrate inside the material. Silicone rubber is less likely to swell, soften, or lose properties. This makes silicone rubber, which has many advantages of its own, even more versatile now.
Properties Of Fluorosilicone Rubber
Oil Resistance
Oil resistance is the most outstanding advantage of Fluorosilicone Rubber. Ordinary silicone rubber will swell and soften when it meets oil or fuel. But Fluorosilicone Rubber has very good oil resistance, it can contact with oil and fuel for a long time, and the volume will not change greatly. Fluorosilicone Rubber often contacts the following oils and has good adaptability. Including: petroleum, diesel, Jet fuel, and lubricating oil.
Electrical Insulation
Fluorosilicone Rubber has the same electrical insulation properties as ordinary silicone. This is a fundamental characteristic of silicone rubber. However, Fluorosilicone Rubber can be used for electrical parts in oil-based environments, and this property is stable for a long time. In addition to oil environments, Fluorosilicone Rubber can maintain stable electrical insulation in humid environments and environments with large temperature variations.
Flame Retardancy
Fluorosilicone Rubber remains relatively stable at high temperatures and under open flames. It has excellent flame resistance and thermal stability. In flammable environments such as oils, it reduces the likelihood of combustion. Even if there is an open flame, it does not keep burning, and the rate of spreading of combustion is very slow. And the smoke produced is very low. However, the magnitude of its flame resistance is related to the formulation, and not all Fluorosilicone Rubber has a high level of flame resistance.
Temperature Resistance
The temperature resistance of fluoro-silicone rubber remains due to the molecular chain of silicone-oxygen bonding that takes place. Silicone-oxygen bonds have high bonding energy, making it possible to maintain good temperature resistance in different temperature ranges. At high temperatures, it is not easy to soften and decompose. At low temperatures, it remains flexible and does not become brittle or crack. Even if the environment of hot and cold cycles, fluoro-silicone rubber can still stabilize the performance of unchanged, the expansion and contraction of the magnitude of change is very small.
Limitations Of Fluorosilicone Rubber
The above mentioned advantages of Fluorosilicone Rubber, but you do not think that it is omnipotent, the next step is to introduce you to what limitations it has, to prevent you from using the wrong scenario.
Not Suitable For Dynamic Sealing Applications
If there are external forces repeatedly causing Fluorosilicone Rubber friction or causing it to move back and forth, the surface is easy to wear and produce small cracks. Fluorosilicone Rubber is soft, not very hard, and does not have high mechanical strength. If it is repeatedly stretched or compressed, it may be deformed or torn. Once a crack occurs, its sealing function will be ineffective.
Limited Resistance to Strong Acids, Bases, and Certain Chemicals
When exposed to strong acids, bases, or oxidizing agents, the silicone-oxygen bonds in Fluorosilicone Rubber can be hydrolyzed or broken, and you will see degradation or swelling as a result. Fluorinated side chains only help Fluorosilicone Rubber to be oil resistant, but they are not a panacea. If Fluorosilicone Rubber is exposed to strong acids and bases at high temperatures, its resistance will be reduced faster.
Differences Between Fluorosilicone Rubber And Conventional Silicone Rubber
The main difference between them is the difference in chemical structure. Fluorosilicone Rubber has more fluorine atoms than ordinary silicone, so it is more resistant to oils, solvents, and fuels than ordinary silicone.
The main difference between the two has already been mentioned in the previous introduction of components and properties. However, you may not be able to understand the difference between the two, so we have made a comparison table for you to get a clear and quick grasp of the differences between the two. However, you have to understand that Fluorosilicone Rubber is not an upgraded version of ordinary silicone; it is a special silicone produced for the fuel environment.
| Feature / Item | Fluorosilicone Rubber | Conventional Silicone Rubber |
| Oil / Fuel Resistance | Excellent – fluorinated side chains allow long-term exposure to gasoline, diesel, aviation fuel, and lubricants | Moderate – prone to swelling, softening, and performance loss when exposed to oils |
| Chemical Resistance | Good resistance to weak acids, weak bases, and some solvents; limited against strong acids/bases | Sensitive to organic solvents; overall chemical resistance is lower than that of fluorosilicone |
| High Temperature Resistance | Can withstand 200–250°C long-term, stable high-temperature performance | Moderate, 200–230°C; performance may degrade in high-temperature oil environments |
| Low Temperature Flexibility | Maintains flexibility at low temperatures, remains elastic without cracking | Flexible at low temperatures, but performance can be affected in oil environments |
| Flame Retardancy | Low flammability; flame spread is limited even in oil/fuel environments | Moderate flame resistance; oils can accelerate burning |
| Mechanical Strength / Dynamic Sealing | Good elasticity but moderate wear and tear resistance; not suitable for high-speed reciprocating seals | Elasticity is moderate; mechanical strength is limited; dynamic sealing is also limited |
| Cost | Relatively high – higher raw material and processing costs | Low – mature process, cost-effective |
| Typical Applications | Automotive fuel systems, aerospace engine compartments, oil pipeline seals, chemical and high-temperature resistant seals | General sealing, food-contact components, and general industrial equipment |
| Food Contact | Can be food-grade with a specific formulation (compliant with FDA/LFGB) | Can be food-grade with adjusted formulation |
| Electrical / Electronic Applications | Stable in oil and high-temperature environments; suitable for demanding electrical insulation | Adequate for general environments; performance is limited under oil or high-temperature conditions |
Applications Of Fluorosilicone Rubber
Automotive Industry
Fluorosilicone Rubber’s oil resistance is suitable for use in fuel-based applications, where it will not swell or soften with prolonged exposure to oil. Including gasoline, diesel, and lubricating oil. It is suitable for static sealing; it can be used to make fuel system seals, engine compartment O-rings, gaskets, and lubricant line seals.
Aerospace
This industry sector operates in complex environments, often with high and low temperatures and different chemical media. Fluorosilicone Rubber is used to make seals in engine compartments, O-rings for fuel systems, and seals for hydraulic systems, which maintain the long-term reliability of the seals. Fluorosilicone Rubber is used for engine compartment seals, fuel system O-rings, and hydraulic system seals, and can maintain the long-term reliability of the seals, because it is resistant to high and low temperatures, and has good flame retardancy and non-polar chemical media.
Chemical Industry
It is often used as a seal for chemical lines, valves, pump body seals, and flange gaskets. These environments do not have strong acids and alkalis. Fluorosilicone Rubber is resistant enough to withstand.
Food & Pharmaceutical Industry
Formulated to meet FDA or LFGB standards, Fluorosilicone Rubber is both safe and durable, and can be used to make seals for food machinery, gaskets for conveying piping, and dairy and beverage processing equipment.
Electronic & Electrical Equipment
The environment of equipment in this field is also complex, with high temperatures and oil-based working conditions. Insulating gaskets or sensors made of Fluorosilicone Rubber can maintain stable dielectric properties and protect electronic components.
FAQ
What Is The Temperature Range Of Fluorosilicone Rubber?
High temperature resistance: can withstand high temperatures of 200-250°C
Low temperature resistance: can withstand low temperatures of -60°C to -70°C
What Grades Of Fluorosilicone Rubber Are Available?
Fluorosilicone Rubber is generally classified into the categories of use, strength, and hardness. The type of application includes: Type 1 and Type 2. Strength grade is divided into two categories: Class 1 and Class 2. The hardness level is divided into three levels, with the higher the number, the harder it is. Below is a table to show you.
| Category | Grade / Value | Description | Typical Applications |
| Type (Application Type)
| Type 1 | Designed for O-rings, optimized elasticity, and sealing | Automotive fuel system seals, aerospace engine compartment O-rings, hydraulic seals |
| Type 2 | For molded parts, sheets, or extrusions, high shape flexibility | Industrial sealing strips, gaskets, and electronic component pads | |
| Class (Strength Level)
| Class 1 | General-purpose material, suitable for standard mechanical load | Most standard sealing applications |
| Class 2 | High-strength material, better resistance to pressure and tearing | High-pressure hydraulic systems, heavy-duty mechanical seals | |
| Grade / Shore A (Hardness Level)
| 40A, 50A | Softer, good elasticity, suitable for light-load seals | Light-load O-rings, flexible gaskets |
| 60A, 70A | Medium hardness, balanced performance | Most commonly used grade, suitable for general industrial and automotive seals | |
| 75A, 80A | Harder, high-pressure resistance, suitable for heavy-load seals | High-pressure hydraulic seals, heavy-duty sealing components |
Is Fluorosilicone Rubber Safe For Food Contact Applications?
Only a specific formulation of Fluorosilicone Rubber can be used as a food-grade material. It needs to comply with FAD or LFGB certification.
How Does Fluorosilicone Rubber Compare To FKM Or Viton®?
| Property | Fluorosilicone Rubber | FKM / Viton® |
| Oil & Fuel Resistance | Stable in contact with fuels and oils; excellent oil resistance | Similar, resistant to fuels and oils |
| High Temperature Resistance | 200–250 °C | 250–300 °C; some high-temperature formulations perform even better |
| Low Temperature Flexibility | Excellent; remains flexible at low temperatures without cracking | Lower; limited flexibility at low temperatures |
| Chemical Resistance | Good resistance to weak acids, weak bases, and some solvents; limited against strong acids/bases | Stronger resistance to acids, bases, and oxidizers; broader overall chemical resistance |
| Processability & Cost | Easy to process; slightly higher cost | Higher cost; more difficult to process; slightly better mechanical strength |
Final Thought
As you can see, Fluorosilicone Rubber is a high-performance material made for special and complex working conditions, not an upgraded substitute for silicone. It has the temperature resistance and flexibility of ordinary silicone rubber, as well as the resistance to oil, fuel, and non-polar chemical media. However, there are some limitations, so you need to consider your actual working conditions before making a decision.
Legensilicone is a well-established company that has been developing and producing Fluorosilicone Rubber for many years. We can produce different types and grades of Fluorosilicone Rubber, which can be used in different working conditions. Whether it is O-ring gaskets for automotive fuel systems or seals for aircraft engine compartments, food processing equipment, electronic component seals, etc., the Fluorosilicone Rubber we design and produce can guarantee the quality and long-term stability of use.
