Is Viton Better Than Silicone?

When it comes to selecting materials for sealing and gaskets, Viton and silicone are two popular options. But how do they compare, and which is the better choice?

Viton and silicone are both high-performance materials, Viton excels in extreme heat resistance, withstanding temperatures up to 600°F. Silicone, however, outperforms Viton in colder environments, maintaining flexibility at temperatures as low as -150°F, a significantly lower range than Viton and many other materials.

Keep reading to find out which material might be better suited for your specific needs and the key differences that can affect your decision.

What is Viton?

Viton is a brand name for a type of fluoropolymer elastomer, often used in industrial sealing applications. It’s known for its resistance to high temperatures, chemicals, and oils. Viton is widely used in industries like automotive, aerospace, and chemical processing.

Viton is a highly durable material, offering exceptional resistance to heat, chemicals, and wear, making it ideal for extreme environments.

Viton chemical composition, consisting mainly of fluorine, gives it properties that allow it to withstand higher temperatures than most rubbers. This makes it suitable for applications in harsh conditions, like seals for engines and pumps. However, it’s not as flexible as silicone, which might be necessary for certain applications like food-grade seals or products that need a higher level of compression set resistance. One disadvantage of Viton is that it can be more expensive than other elastomers due to the specialized production process and raw materials required.

What are the Advantages and Disadvantages of Viton?

Viton is a top choice for industrial sealing applications, but like any material, it comes with both strengths and limitations. Understanding these can help you decide if it's the right choice for your project.

Viton offers superior chemical and heat resistance, but its higher cost and limited flexibility might make silicone a better choice in some cases.

The primary advantage of Viton lies in its resistance to extreme conditions. It’s highly resistant to heat and chemical degradation, which makes it invaluable in harsh industrial settings. However, these same properties can also make Viton less versatile in everyday applications where flexibility or lower cost is a priority. For example, while Viton excels in automotive gaskets or aerospace seals, silicone’s high flexibility and lower cost can make it more appealing in areas like HVAC or consumer goods.

Advantages of Viton:

• Chemical Resistance: Viton excels in resisting a wide array of chemicals, oils, fuels, and solvents, making it suitable for demanding industrial and automotive uses. It is also highly resistant to hydrocarbons, biodiesel, and petrochemicals.

• Resistance to Extreme Environments: Viton can withstand extreme temperatures, chemicals, and environmental factors like UV and ozone. It exhibits exceptional resistance to both high and low temperatures (-20°C to +250°C). Viton compounds remain elastic when exposed to laboratory air oven aging up to 204°C, or to intermittent exposures up to 316°C.

• Durability: Viton has a unique set of robust mechanical properties that ensures consistent performance and provides durability in most sealing applications. Its long lifespan reduces maintenance and replacement costs over time.

• Low Gas Permeability: Viton has low gas permeability, which is beneficial in sealing applications as it limits the passing of corrosive or reactive gases.

• Resistance to Aging: Viton demonstrates resistance to aging and degradation which contributes to long-term reliability. Prolonged exposure to most fluids will not cause the rubber to degrade.

• Mold resistance: Viton O-rings are resistant to mold.

Disadvantages of Viton:

• Cost: Viton is more expensive compared to other elastomers like Nitrile. However, its resistance to aging and longevity can justify the higher cost because it needs less frequent replacement.
• Limited Chemical Resistance: Viton may experience a small degree of swelling if exposed to certain chemicals, including ketones, esters, amines, and hot hydrofluoric acids. It is not compatible with ketones, acetone, esters, amines, organic acids, acetic acid, MEK, ethyl acetate, and highly polar chemicals.
• Hardness: Viton rubber can be relatively hard compared to other materials. For applications that require a softer or more flexible material, alternative materials like EPDM or Silicone may be more appropriate.
• Low-Temperature Flexibility: After continual exposure to low or below-freezing temperatures, FKM components can harden and lose their flexibility, making them more brittle and apt to fail during use. Viton is generally serviceable in dynamic applications to temperatures of -18 to -23 °C. Special formulations permit its use in static applications down to -54°C.
• Environmental Concerns: Recycling and disposal can be challenging, raising sustainability issues.
• Toxic Byproduct: During exposure to extreme heat, FKM can produce a toxic byproduct known as hydrogen fluoride, which can cause respiratory problems.

Advantages of Viton	Disadvantages of Viton
Excellent Chemical Resistance	Higher Cost
Withstands Extreme Temperatures & Environments	Limited Compatibility with Certain Chemicals
High Durability & Long Lifespan	Relative Hardness
Low Gas Permeability	Poor Low-Temperature Flexibility
Resistant to Aging & Degradation	Environmental Concerns (Recycling/Disposal)
Mold Resistant	Potential for Toxic Byproduct (Hydrogen Fluoride) at High Heat

Is FKM Equal to Viton?

FKM is a family of fluorocarbon elastomers, and Viton is a registered brand name within the FKM category. While all Viton is FKM, not all FKM elastomers are Viton.

FKM is the general class of elastomers to which Viton belongs, but Viton refers specifically to a certain formulation within this group.

The main difference between FKM and Viton lies in the formulation and performance of specific grades of FKM elastomers. Viton, being a type of FKM, is specifically known for its superior temperature and chemical resistance. Other types of FKM elastomers might not offer the same level of performance but are generally less expensive. If you’re looking for a reliable, high-performance material, Viton is the top choice in the FKM category. However, for less demanding applications, other FKM types might suffice.

Why is FKM So Expensive?

FKM, and particularly Viton, tends to be more expensive due to its manufacturing process and the use of specialized materials that contribute to its unique properties.

The high cost of FKM elastomers comes from the advanced production processes and the need for high-quality raw materials, making them a premium option for industrial applications.

The production of FKM elastomers¹ like Viton requires the use of fluorine-based chemicals, which are more costly than typical rubber components. This specialized process adds to the overall price of the material. Furthermore, the highly controlled manufacturing environment and strict quality assurance processes further inflate costs. These factors contribute to why FKM elastomers are often used in industries that are willing to pay a premium for the performance benefits that Viton and other FKM variants provide.

Factors Contributing to the High Cost of FKM

• Fluorine-Based Chemicals: These raw materials are rare and expensive.
• Complex Manufacturing Process: The production of FKM elastomers requires highly specialized machinery and conditions, adding to the overall cost.

What is the Alternative to Viton?

If Viton’s cost or rigidity is an issue, there are alternatives like silicone, EPDM, or Nitrile rubber, each with their own strengths.

Silicone and EPDM are both lower-cost alternatives to Viton, offering a balance between performance and flexibility depending on the application.

For applications requiring less extreme heat or chemical resistance, silicone can be a cost-effective alternative to Viton. It is also more flexible, which makes it ideal for seals in the food or medical industries. EPDM, on the other hand, is another great alternative that excels in weather resistance and flexibility, making it suitable for outdoor or automotive applications. However, these materials do not match Viton in terms of high-temperature and chemical resistance, so they are typically used in less demanding environments.

Alternatives to Viton

• Silicone²: Flexible, non-toxic, and ideal for low-temperature applications.
• EPDM³: Good for outdoor and automotive applications, but lacks the high chemical resistance of Viton.

What is the Difference Between Silicone and FKM?

While both silicone and FKM are used in sealing applications, their properties are quite different, making each better suited for specific environments.

Silicone is known for its flexibility and lower cost, while FKM, especially Viton, offers superior resistance to heat and chemicals.

Silicone has excellent flexibility and is highly resistant to environmental factors like UV light and ozone, but it doesn’t have the same high-temperature or chemical resistance as FKM. This makes silicone an ideal choice for applications that require flexibility, such as gaskets in food-grade or medical equipment. FKM, particularly Viton, is much better suited for applications that require resistance to extreme temperatures, oils, and fuels, such as in automotive or aerospace industries. The key difference lies in their strength against chemicals and temperature.

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