EPDM is our most commonly extruded elastomer for rubber seals. It is a very good compound for use in outdoor applications as it is very resistant to weathering and ozone exposure (A quick note on ozone exposure: Ozone is found in the air in small quantities but creates an aging effect on elastomers that looks like cracking or dry rot. This reduces the performance of the material and after time will require the replacement of the seal). EPDM is not recommended where the medium it will operate in will have exposure to oils and gas, but it is water resistant and maintains its flexibility in low temperatures. In general EPDM will operate well in a temperature range of -80°F to 300°F.
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Like EPDM, silicone is very resilient against the effects of ozone and UV light. If your application is going to expose it to gas, oil or acids or if it needs to have strong tensile strength it probably wouldn’t be the material of choice. Silicone is a more expensive elastomer than EPDM, but it has some benefits over EPDM that make it the material of choice for some applications. The key benefit that silicone has over EPDM is tolerance to cold and heat. Silicone can operate under conditions from -180°F to 525°F. This ability to withstand high heat makes silicone ideal for uses like sealing autoclaves. Silicone is an expensive option, but critical for extreme heat environments.
Neoprene is resistant to oils, ozone, and water amongst other things. Unlike silicone it resists cracking and abrasions when under stress or impact. Its operating range within cold and hot temperatures is similar to rubber, -80°F to 300°F. Neoprene is used in windows, electrical enclosures, expansion joints and lots of other applications. Neoprene costs a bit more than EPDM but won’t break the bank like a silicone compound.
Nitrile is in the middle of the road from a cost standpoint. It’s a great choice for applications such as oil seals, aircraft hoses, or anywhere resistance to oil, fuel and chemicals is important. Its optimal operating temperature range is from -55°F to 275°F, so not the best choice for extreme temperature ranges. Nitrile doesn’t do well resisting the aging effects of sunlight or exposure to the elements but can be compounded in order to increase its resistance to these effects.
PVC has a limited temperature rating of -20°F to 158°F. PVC is a thermoplastic, which means that it is cured when it cools down. This is very different from the other elastomers in this article, which are thermosets...meaning they cure when heated up. So if PVC gets too hot it can become deformed. PVC can fade in sunlight, but Uni-Grip’s PVC has an additive to reduce the effects of fading, making it a good choice for outdoor conditions. If there will be exposure to oil or gas, then you may want to choose a different material as PVC doesn’t resist these materials well.
When choosing seals, you should consider several factors, including the type of seal, its application, seal material, hardness, and attachment. We manufacture a wide range of seals, including:
We supply a range of seal materials for different environments. Materials may withstand exposure to cold and hot water, fuels, hydraulic fluids, or extreme ambient temperatures. Choices include EPDM synthetic rubbers, nitrile rubber, silicone, and PVC. Many of the seals incorporate a metallic core to increase strength and rigidity. Sponge rubber is used for door seals, while dense rubber has better impact absorption properties. Some seals have a dual durometer with a more rigid mounting material and a less dense seal. Attachment options include flange mounting, pedestal mount, and adhesive mounts.
Buna, ethylene propylene diene monomer (EPDM) and Viton are all similar seal materials, but what makes them different? Choosing the right elastomer or polymer material is important for several reasons. While it may not seem like a major decision, the material chosen determines the quality, life span 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 many issues down the road. Seal material has a long-term effect on an application’s capabilities.
The term high elasticity is known as the ability of an object to return to its shape once it no longer is attached to its source of stress. Rubber compounds represent a wide collection of materials—known as elastomers—which includes base elastomer, vulcanization agents, fillers and plasticizers, with their main feature being high elasticity. Therefore, rubber is widely considered the best seal material. Questions to consider when selecting the seal material for an application include:
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Whether you are choosing Buna (Nitrile), EPDM or Viton, it is important to compare and consider all key features and benefits.
When it comes down to abrasive, water and oil resistant and super-strength properties, Buna is a cost-effective elastomer. Buna, also referred to as Nitrile rubber, is commonly known as the industry’s most economical seal material. Buna is well known for its mechanical performance and is a 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. 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 poor acid and mild alkali resistance, Buna can also withstand low temperatures. Buna is limited in extreme factors such as high temperatures, weather, sunlight and steam resistance applications. It is also not suitable with clean-in-place (CIP) sanitizing agents containing acids and peroxides, such as OXONIA.
When considering flexibility, strength, weather resistance and the ability to withstand extreme conditions, EPDM is a good option. EPDM is a type of synthetic rubber and a commonly used elastomeric material for automotive, construction and mechanical applications. More expensive than Buna, it can withstand a variety of thermal, weather and mechanical properties because of its long-lasting high tensile strength. It is ideal for applications involving water, chlorine, bleach and other alkaline materials. From waterproofing to HVAC, EPDM is used for a variety of applications because of its resistance to weathering, ozone and deionized water.
With elastic and adhesive properties, once stretched, EPDM returns to its original shape regardless of the temperature. EPDM is not recommended for petroleum oil, fluids, chlorinated hydrocarbon or hydrocarbon solvent applications.
Viton is the more expensive option, but it is a solution for applications exposed to extreme weather, ozone and chemical degradation. Viton is a long-lasting, high-performance, fluorinated, hydrocarbon rubber product most commonly used in O-Rings and seals. Resistant to ozone, oxidation and extreme weather conditions, including materials such as aliphatic and aromatic hydrocarbons, halogenated fluids and strong acid materials, Viton is one of the more robust fluoroelastomers. Designed to withstand extreme temperatures, Viton seals are the preferred option for the most challenging and demanding sealing needs.
Viton can provide support for a broad range of substances and features and has resistance to high temperatures and resilience capabilities.
Choosing the correct polymer is important. While all seal materials are similar, each polymer serves a variety of purposes to meet any specific need.
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