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.
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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:
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.
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Choosing the correct polymer is important. While all seal materials are similar, each polymer serves a variety of purposes to meet any specific need.
Oil seals, also referred to as shaft seals, are widely used to prevent the leakage of medium (such as oils and grease) along a rotating shaft. This leak prevention is primarily achieved by the sealing element which can be made from a wide range of materials that are chosen according to each application. They are commonly used in gearboxes, hydraulic cylinders, and related components.
An oil seal is designed to perform three major functions: to prevent lubricants from leaking outside the seal even under high pressure, to act as a barrier to retain the lubricating oil, and to prevent dirt and other contaminants from entering the unit.
Shop for Oil SealsOil seals normally consist of three basic components: the sealing element, the metal case, and garter spring.
The sealing element makes up the interior of the oil seal, and the materials commonly used are:
The metal case is the exterior (or frame) of the oil seal, the principal function of which is to give rigidity and strength to the seal. The material of the case must be selected depending on the environment where the seals are to be used. Often the metal case is covered by the same rubber material used in the sealing element, which also helps seal the exterior of the oil seal in the housing bore. Common case material types are:
The garter spring is located at the end of the primary sealing lip and used to apply pressure to the sealing lip against the shaft. Common garter spring material types are:
Global O-Ring and Seal carries a full line of oil seals in all industry standard sizes and has the ability to create custom oil seals. If you are a distributor or user of oil seals who may have need for our services, contact us today to speak with one of our team members, request a no-obligation quote, or place an order from our extensive inventory at GlobalOring.com.
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