Comparison of O-Ring Materials

While selecting an O-ring for your application, a lot ofmakes Viton an ideal choice for high temperature
importance should be placed on the material of theapplications as well as applications exposed to a
seal being used. Since a proper sealing action is highlyvariety of different fluids. One such application that
dependent on the condition of your O-ring, it ishas adopted Viton O-rings is SCUBA diving, where
important that an O-ring material be chosen to bestthe O-ring seals are used in the diver's air tank.
suit the operating environment of your application.However, though Viton is compatible with most
Some of the common materials used to makehydrocarbons, it is generally not compatible with
O-rings are nitrile rubber or Buna-N, Viton(r), siliconeketones and organic acids.
rubber, neoprene, and PTFE or Teflon(r).PTFE:
Choosing an O-ring material is dependent on aOne fluoropolymer commonly used to manufacture
number of different factors, but two of the mostO-rings is PTFE, or Teflon(r), as it is commonly
critical factors are the operating temperature rangeknown. PTFE is one of the most chemically inert
that O-rings are subjected to and the differentmaterials used to make O-rings and extremely
chemicals they may be exposed to. Some additionalresistant to oils, solvents, bases, acids, steam, and
factors that play a role in the selection of an O-ringvarious other chemicals. Its unparalleled resistance to
material include resistance to tearing and abrasion,abrasion and tearing makes it ideal for dynamic
and sunlight or aging. Since most O-ring materialssealing applications. However, there are few
react differently to diverse environments as well asdrawbacks to using PTFE O-rings. The first one is
chemicals, each material has its own advantages andtheir inability to be compressed as effectively as
disadvantages.other commonly used O-ring materials, which
Nitrile Rubber:translates into inefficient sealing. The other major
One of the most common materials used to makedisadvantage of this material is its poor cold flow
O-rings is nitrile rubber or Buna-N, which is a syntheticcharacteristics under constant strain. Still, its chemical
rubber copolymer. This material has excellentresistance and low coefficient of friction has made it
resistance to water, hydraulic fluids, solvents, oils anda popular sealing option in many valves and other
other petroleum products. This feature, coupled withapplications.
its operating temperature range of between -65Neoprene:
degrees F to +275 degrees F, has made nitrile rubberNeoprene is yet another synthetic rubber that is
one of the most widely used elastomers to makeregularly used to make O-ring seals. This elastomer is
O-ring seals. However, this material does have itsresistant to animal and vegetable fats, as well as
limitations; nitrile is generally not recommended formost oils and solvents. However, O-ring seals made
applications where it might be exposed to sunlightfrom this material are generally not recommended for
and ozone, as well as certain chemicals, which includeapplications that involve exposure to ketones, esters,
ketones, esters, and aromatic hydrocarbons.aromatic hydrocarbons, and strong oxidizing acids.
Furthermore, its susceptibility to ozone also makes itNatural Rubber:
necessary that nitrile rubber seals are not stored nearAt present, natural rubber O-rings are rarely used due
electric motors that normally generate ozone. Its highto the advent of synthetic elastomers, such as Nitrile
resistance to petroleum products and reasonablerubber and Viton. Natural rubber can be used with
resistance to temperature has led to Nitrile rubberanimal oils, vegetable oils, and most oxidizing
O-rings becoming the first choice for variouschemicals. However, it is not recommended for use
applications in the automobile industry.with oils, petroleum solvents, aromatic hydrocarbons,
Silicone Rubber:and in applications that demand exposure to sunlight
Silicone rubbers are a collection of elastomericor ozone.
polymers produced from silicon, hydrogen, oxygen,These listed materials are commonly used elastomers
and carbon. Silicones generally have poor resistancefor making O-rings, but other materials, such as
to abrasion and tearing, as well as low tensileKalrez, are also used in certain special applications.
strength plus high co-efficient of friction - featuresKalrez is an ideal replacement for Viton in applications
that make them unsuitable for dynamic sealingthat have operating temperatures of up to 500
applications. However, its exceptional resistance todegrees F. Similarly, there are various other
extreme temperatures, ranging from as low as -150elastomers used for specific sealing purposes.
degrees F to as high as +500 degrees F, makes itWhatever the material you choose for your
ideal for applications where seals are exposed to highapplication, care should be taken to ensure its
dry heats, as in automotive components andcompatibility with operating temperatures, fluids, and
cookware.environment.
Viton(r):The criticality of choosing the best material for your
Viton(r) is another synthetic rubber commonly usedapplication is right away apparent when we consider
for making O-ring seals, which is a type of FKMthe cause of Space Shuttle Challenger disaster. This
elastomer. This elastomer's excellent resistance totragedy was caused by the failure of an O-ring that
solvents and oils, as well as its resistance to broadlost its elasticity and became brittle due to an
operating temperature ranges, has made it a popularunexpected drop in ambient temperature. Though
for use in a number of applications. Though itsmost O-ring failures might not lead to the loss of life
operating temperature ranges from -10 to +400at par with this disaster, there is no denying the
degrees F, seals made from this material are knowndefinite economic loss caused by a failed machine or
to withstand temperatures as high as +600 degreesdevice.
F for short times. This combination of properties