EPDM, an acronym for Ethylene Propylene Diene Monomer; and Nitrile Rubber, commonly known as Buna-N rubber, are both synthetic rubber compounds. They are among the many synthetic rubber compounds that are loosely grouped or mistakenly called Neoprene, although like Neoprene, they have arisen out of a multitude of synthetic rubber applications that have specific characteristics. It is in these properties that they widely differ, which also lends them to different applications.
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Ethylene Propylene Diene Monomer is strong and abrasion resistant, and handles polar substances such as water, coolants and steam well. It weathers extremely well. Therefore it finds widespread use in rubber roofing, gaskets, seals, weather sealing around windows and automotive and other coolant hoses. On the other hand, it doesn't do so well with oils and petroleum-based products. Its physical resilience make it good for moving or vibrating applications, such as equipment mounts, drive belts and washers.
Nitrile rubber, widely known as Buna-N, fares a little less well with physical challenges and much worse with weathering. However Buna-N is valued for its resistance to oil petroleum-based products and many chemicals. Therefore it is completely useful for fuel and oil hoses and seals, and other challenging under-hood applications in the automotive sector because of its temperature characteristics. Nitrile rubber gloves are also common for protecting hands against constant exposure to most chemical compounds.
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EPDM is used in areas where weatherproofing, sealing and vibration control are important. It is very good for the constant barrage of environmental challenges such as sunlight and ozone It is physically resilient and useful for motion damping mounts. Buna-N tends to have more purpose in industrial applications with its greater resistance to chemicals and oils. It is widely used as an alternative to latex rubber wherever allergenic or anaphylactic shock concerns are prevalent.
Comparative Use as Washers
Synthetic rubber flat washers are used for both sealing and vibration damping purposes. The first factor to consider when selecting a rubber washer material is the primary purpose of using an elastomeric washer in the first place. Many sealing applications can be accomplished with sealing compounds on the threads of the fasteners.
The other factor is the amount of pressure that the sealing application will have to sustain. Synthetic rubbers also have a tendency to take a set, meaning that round O-ring type seals or flat-washer type seals will flatten over time if they are squeezed too tightly. This puts them beyond their range of elasticity, which is very important to the longevity of the seal.
If the purpose is purely vibration damping, then the primary consideration will be absorbing continual vibration over time, as long as the material is compatible with the chemical and environmental challenges of the application.
The costs of raw materials for producing synthetic rubber compounds vary widely. If the basis of the elastomeric is highly dependent on petroleum markets because it is a derivative of petroleum by-products, the price of the finished good could fluctuate significantly and often. If there is less influence due to oil prices, one material could edge out the other. As long as the chemical resistance and weather compatibility are considered, many companies purchasing large amounts of either component will look at price as the determining factor.