While selecting an O-ring for your application, a lot of importance needs to be positioned on the fabric from the seal being utilized. Since an appropriate sealing action is tremendously dependent on the fitness of your O-ring, it is vital that an O-ring material be chosen to work best with the operating environment of the application. Several of the common materials employed 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 determined by several different factors, but two of the more critical factors would be the operating temperature range that O ring are exposed to and the different chemicals they may be subjected to. Some additional factors that be a factor in picking an O-ring material include effectiveness against tearing and abrasion, and sunlight or aging. As most O-ring materials react differently to diverse environments as well as chemicals, each material has its own benefits and drawbacks.
One of the most common materials utilized to make O-rings is nitrile rubber or Buna-N, which is a synthetic rubber copolymer. This product has excellent potential to deal with water, hydraulic fluids, solvents, oils along with other petroleum products. This feature, along with its operating temperature range of between -65 degrees F to 275 degrees F, makes nitrile rubber just about the most widely used elastomers to create O-ring seals. However, this material has its limitations; nitrile is normally not recommended for applications where it will be exposed to sunlight and ozone, and also certain chemicals, which include ketones, esters, and aromatic hydrocarbons. Furthermore, its inclination towards ozone also will make it necessary that nitrile rubber seals usually are not stored near electric motors that normally generate ozone. Its high resistance to petroleum products and reasonable potential to deal with temperature has led to Nitrile rubber O-rings becoming the first selection for various applications in the automobile industry.
Silicone rubbers are a selection of elastomeric polymers made out of silicon, hydrogen, oxygen, and carbon. Silicones usually have poor potential to deal with 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 resistance to extreme temperatures, which range from as little as -150 degrees F to up to 500 degrees F, will make it ideal for applications where seals are in contact with high dry heats, as in automotive components and cookware.
Viton(r) is yet another synthetic rubber commonly used to make O-ring seals, which is a kind of FKM elastomer. This elastomer’s excellent effectiveness against solvents and oils, along with its resistance to broad operating temperature ranges, made it a well known for use in a number of applications. Though its operating temperature ranges from -10 to 400 degrees F, seals made out of this product are acknowledged to withstand temperatures as much as 600 degrees F for brief times. This blend of properties makes Viton a perfect selection for high temperature applications and also applications open to many different different fluids. A great application that has adopted Viton O-rings is Deep-sea diving, in which the O-ring seals are employed inside the diver’s air tank. However, though Viton is compatible with most hydrocarbons, it is generally not appropriate for ketones and organic acids.
One fluoropolymer popular to manufacture O-rings is PTFE, or Teflon(r), as it is commonly known. PTFE is one of the most chemically inert materials accustomed to make O-rings and intensely resistant against oils, solvents, bases, acids, steam, as well as other chemicals. Its unparalleled potential to deal with abrasion and tearing can make it ideal for dynamic sealing applications. However, there are few drawbacks to using PTFE O-rings. The first one could be the inability to be compressed as effectively as other widely used O-ring materials, which translates into inefficient sealing. Another major drawback to this product 98dexipky its poor cold flow characteristics under constant strain. Still, its chemical resistance and low coefficient of friction makes it a common sealing option in several valves along with other applications.
Neoprene is another synthetic rubber that is regularly used to make O-ring seals. This elastomer is resistant to animal and vegetable fats, along with most oils and solvents. However, O-ring seals produced from this product are usually not advised for applications that entail contact with ketones, esters, aromatic hydrocarbons, and powerful oxidizing acids.
Presently, natural rubber O-rings are rarely used due to introduction of synthetic elastomers, such as Nitrile rubber and Viton. Natural rubber can be utilized with animal oils, vegetable oils, and a lot oxidizing chemicals. However, it is really not suitable for use with oils, petroleum solvents, aromatic hydrocarbons, and in applications that demand contact with sunlight or ozone.
These listed materials are commonly used elastomers for making O-rings, but many other materials, like Kalrez, are also utilized in certain special applications. Kalrez is an ideal alternative to Viton in applications which may have operating temperatures up to 500 degrees F. Similarly, there are various other elastomers used for specific sealing purposes. No matter what material you decide on for the application, care needs to be taken up ensure its compatibility with operating temperatures, fluids, and environment.
The criticality of determing the best material to your application is immediately apparent whenever we consider the reason for Space Shuttle Challenger disaster. This tragedy was brought on by the failure of your 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 cause the loss in life at par using this disaster, there is no denying the definite economic loss the result of a failed machine or device.