While selecting an O-ring for your application, lots of importance ought to be positioned on the content of the seal being used. Since an appropriate sealing action is very influenced by the fitness of your O-ring, it is important that an O-ring material be chosen to work best with the operating environment of your respective application. Some of the common materials used to make O-rings are nitrile rubber or Buna-N, Viton(r), silicone rubber, neoprene, and PTFE or Teflon(r).
Choosing an O-ring material is reliant on a variety of factors, but two of the very critical factors would be the operating temperature range that O ring are put through and the different chemicals they may be subjected to. Some additional factors that are involved in the selection of an O-ring material include effectiveness against tearing and abrasion, and sunlight or aging. Since most O-ring materials react differently to diverse environments and also chemicals, each material features its own positives and negatives.
One of the most common materials used to make O-rings is nitrile rubber or Buna-N, which is actually a synthetic rubber copolymer. This product has excellent effectiveness against water, hydraulic fluids, solvents, oils along with other petroleum products. This feature, in addition to its operating temperature selection of between -65 degrees F to 275 degrees F, has made nitrile rubber probably the most widely used elastomers to create O-ring seals. However, this material is equipped with its limitations; nitrile is usually not advised for applications where it could be subjected to sunlight and ozone, as well as certain chemicals, such as ketones, esters, and aromatic hydrocarbons. Furthermore, its inclination towards ozone also causes it to be necessary that nitrile rubber seals are not stored near electric motors that normally generate ozone. Its high resistance to petroleum products and reasonable resistance to temperature has led to Nitrile rubber O-rings becoming the 1st choice for various applications in the automobile industry.
Silicone rubbers are an accumulation of elastomeric polymers produced from silicon, hydrogen, oxygen, and carbon. Silicones usually have poor effectiveness against abrasion and tearing, along with low tensile strength plus high co-efficient of friction – features that make them unsuitable for dynamic sealing applications. However, its exceptional potential to deal with extreme temperatures, ranging from only -150 degrees F to as much as 500 degrees F, causes it to be perfect for applications where seals are open to high dry heats, like automotive components and cookware.
Viton(r) can be another synthetic rubber frequently used to make O-ring seals, which is a kind of FKM elastomer. This elastomer’s excellent potential to deal with solvents and oils, along with its potential to deal with broad operating temperature ranges, makes it a favorite for usage in many applications. Though its operating temperature ranges from -10 to 400 degrees F, seals created from this product are acknowledged to withstand temperatures up to 600 degrees F for short times. This mix of properties makes Viton a perfect choice for high temperature applications as well as applications exposed to various different fluids. One such application which includes adopted Viton O-rings is Deep-sea diving, where the O-ring seals are utilized in the diver’s air tank. However, though Viton works with most hydrocarbons, it is generally not works with ketones and organic acids.
One fluoropolymer widely used to produce O-rings is PTFE, or Teflon(r), as it is commonly known. PTFE is probably the most chemically inert materials utilized to make O-rings and really resistant to oils, solvents, bases, acids, steam, as well as other chemicals. Its unparalleled resistance to abrasion and tearing will make it ideal for dynamic sealing applications. However, you can find few drawbacks to using PTFE O-rings. The first could be the inability to be compressed as effectively as other popular O-ring materials, which means inefficient sealing. One other major disadvantage of this product 98dexipky its poor cold flow characteristics under constant strain. Still, its chemical resistance and low coefficient of friction has created it a common sealing option in several valves and other applications.
Neoprene is another synthetic rubber that is regularly utilized to make O-ring seals. This elastomer is proof against animal and vegetable fats, along with most oils and solvents. However, O-ring seals created from this product are often not advised for applications which entail contact with ketones, esters, aromatic hydrocarbons, and robust oxidizing acids.
Currently, natural rubber O-rings are rarely used because of the introduction of synthetic elastomers, like Nitrile rubber and Viton. Natural rubber may be used with animal oils, vegetable oils, and many oxidizing chemicals. However, it is not recommended for use with oils, petroleum solvents, aromatic hydrocarbons, and in applications that demand contact with sunlight or ozone.
These listed materials are typically used elastomers for producing O-rings, but many other materials, such as Kalrez, can also be found in certain special applications. Kalrez is a perfect replacement for Viton in applications which may have operating temperatures as high as 500 degrees F. Similarly, there are various other elastomers used for specific sealing purposes. Whatever the material you end up picking for your personal application, care must be delivered to ensure its compatibility with operating temperatures, fluids, and environment.
The criticality of choosing the best material for the application is without delay apparent if we consider the main cause of Space Shuttle Challenger disaster. This tragedy was brought on by the failure of an O-ring that lost its elasticity and became brittle on account of an unexpected drop in ambient temperature. Though most O-ring failures might not exactly lead to the reduction in life at par with this particular disaster, there is absolutely no denying the definite economic loss the effect of a failed machine or device.