Buna, EPDM, Viton® are all similar seal materials but what stands each of these apart? Choosing the right elastomer or polymer material is important for a number of reasons. While it may not seem like a major decision, the material chosen determines the quality, lifespan, and performance of an application. From snapping to peeling to breaking; a seal material that is a poor fit for an application can lead to a number of issues down the road. Seal material has a long-term effect on your application’s capabilities.
The information outlined below will offer guidance and provide the best solution based on the most defined aspects of your application including:
- Impact and temperature resistance
- Compression strength
- Assembly and physical properties
- Weather conditions
- Chemical compatibility
First Item to Consider: What Does High Elasticity Mean?
The term “high elasticity” is known in the industry as the ability of an object to return to its shape once it no longer is attached to its source of stress. Rubber compound represents a wide collection of materials – known as elastomers – which includes base elastomer, vulcanization agents, fillers, and plasticizers its main feature being high elasticity. Therefore, rubber is widely considered the best material for objects known as “seal materials”.
Questions to consider when selecting the right seal material for an application include:
- Will this application be exposed to water, oil, gas, harsh chemicals, or other materials?
- What is the minimum and maximum temperature resistance?
- What is the required compression strength?
- Will this application be exposed to sunlight for hours at a time?
Whether you’re choosing Buna (Nitrile), EPDM, or Viton®, it’s important to compare and consider all key features and benefits.
BUNA
When it comes down to abrasive, water and oil resistant, and super-strength properties; Buna is the most cost-effective elastomer. Buna, also referred to as Nitrile rubber, is commonly known as the industry’s most economical option in the wide variety of seal material options to choose from. Buna is well known in the industry for its mechanical performance and is the top performer when it comes down to oil-based, petrochemical, and chemical applications. The more Nitrile in a polymer means a higher resistance to chemicals, acids, and other oils.
Therefore, Buna is widely used in the industry for crude oil, water, various alcohol, silicone grease, and hydraulic fluid applications due to its inflexibility.
Buna is comprised of synthetic rubber copolymer that performs well in applications requiring metal adhesion and abrasion-resistant material – this chemical background makes it ideal for sealant applications. Designed with a moderately poor acid and mild alkali resistance, Buna can also withstand low temperatures. However, Buna is limited to extremely high temperatures, can be weather and sunlight resistance, and steam resistance – making it limited to more extreme applications. Buna is also not suitable with CIP sanitizing agents containing acids and peroxides, such as OXONIA.
Key advantages and benefits to consider about Buna include:
- Economical and affordable
- Strong and sturdy elongation
- Good for oil and water resistance
- Features a low compression set
- High abrasion resistance
- Heavy duty strength
- Wide range in temperature resistance
- Heat resistant and cold resistant
Disadvantages of Nitrile rubber include:
- Limited extreme temperature resistance
- Poor flame resistance
- Not suitable for hydraulic liquids, brake fluids, ketones, and acetates
- Limited sunlight, weather, and ozone resistance
Key applications for Nitrile rubber in the valve industry:
- Sealants
- O-rings
- Molded products
EPDM
When considering flexibility strength, weather resistance, and the ability to withstand extreme conditions, EPDM is an excellent option. EPDM, also known as Ethylene Propylene Diene Monomer, is a specific type of synthetic rubber and one of the most commonly used elastomeric materials for automotive, construction, and mechanical good applications. Slightly more expensive when compared to Buna, it can withstand a variety of thermal, weather, and mechanical properties because of its long-lasting high tensile strength. It’s ideal for applications that involve water, chlorine, bleach, and other alkaline materials. From waterproofing needs to HVAC needs, EPDM is used for a variety of industrial applications because of its resistance to weathering, ozone, and deionized water. With both elastic and adhesive properties, once stretched EPDM always returns to its original shape regardless of the temperature. However, EPDM is not recommended for petroleum oil, fluids, chlorinated hydrocarbon, or hydrocarbon solvent applications.
Key advantages to consider about EDPM includes:
- Wide operational temperature range
- Suitable for extreme environment and cold materials
- Superior ozone and sunlight resistance
- Good compression set
- Sturdy tear, abrasion, and steam resistance
- High tolerance to sodium hydroxide solutions, diluted acids, ketones, and alkalis
- Versatile for a number of applications including but not limited to the industrial and HVAC industries
Disadvantages of EPDM include:
- Easy to damage
- Poor resistance to petroleum-based fuels
- Difficult to adhere to
- Not compatible with a variety of oils or acids
EPDM is used across a wide range of industrial applications, including:
- Seals and O-rings
- Tubing
- Washers
VITON®
Viton® is the more expensive option over BUNA and EPDM seals but it’s the perfect high-end solution for applications exposed to extreme weather, ozone, and chemical degradation. Significantly more expensive when compared to EPDM and Buna, Viton® is a long-lasting high-performance fluorinated hydrocarbon rubber product most commonly used in O-Ring and seals for the valve industry. Excellent for resistance to ozone, oxidation, and extreme weather conditions — including a variety of materials such as aliphatic and aromatic hydrocarbons, halogenated fluids, strong acid materials — Viton® is one of the robust fluoroelastomers. Designed to withstand extreme temperatures, Viton® seals are the preferred option for the most challenging and demanding sealing needs.
Viton® is able to provide support for an extremely broad range of substances and features exceptional good resistance to high temperatures and excellent resilience capabilities.
Key advantages to consider about Viton® include:
- Powerful when under pressure
- High-temperature performance
- Outstanding chemical compatibility among a wide variety of chemicals and acids
- Retains flexibility and elasticity in high-pressure applications
- Excellent use for sterilization
- High-heat resistance
- Absorbs fluids quickly and efficiently
- Longer life span
- Environmentally-friendly
Disadvantages of Viton® include:
- More expensive than Nitrile
- Incompatible with ketones
- Not as strong or effective in lower temperatures
Reliable material for:
- O-Ring applications
- Pumps and valves
- Seal leaks
As noted above, choosing the correct polymer is highly important for a variety of reasons. While all seal materials are similar, each polymer serves a wide variety of purposes to meet your specific need. If you need further assistance choosing the right rubber material or polymer for your valve application, please contact Flomatic Valves by visiting Flomatic.com or calling (800) 833-2040.
