O'ring Elastomer Application Guide

O’ring Elastomer Application Guide

The table below is a general application guide for the most common o’ring compounds. This table is to be used as a guide only. The user is ultimately responsible for selecting the right compound. Our sales staff at Sealing Australia can assist you in compound selection, so please contact us for assistance.

Oring Elastomer guide

Brief on o’ring elastomers.

Compound Temperature Range Physical Characteristics Shelf Life
As per ARP 5316
Chemical Compatibility
(Compatible)
Chemical Compatibility
(Not Compatible)
NBR (Nitrile) Acrylonitrile-Butadine: Most commonly found o’ring elastomer. Found in hydraulic systems, drinking water and many other applications. Heat Resistance: Up to 100°C with short excursions to 121°C

Cold Flexibility: Elasticity retained down to between -34°C to -57°C, depending on the grade of nitrile used.

Abrasion resistance: Good

Compression set: Very good

Tear resistance: Fair to good

Tensile strength: Very good

Permeability resistance: Good

15 Years Aliphatic hydrocarbons (propane, butane, natural gas)

Diesel fuels and diesel oils

Vegetable and mineral oils & greases

HFA, HFB and HFC hydraulic fluids

Dilute acids, alkali and salts at low temperatures

Water up to 100°C (AS/NZS4020 approved drinking water grades available)

Ammonia gas, cold

Fuels with high aromatic content

Aromatic and chlorinated hydrocarbons such as benzene, toluene, trichloroethylene and carbon tetrachloride

Polar solvents such as ketone, acetone, acetic acid and ethylene-ester

Glycol based brake fluid (DOT 3 & 4)

Bad ozone, weather and atmospheric aging resistance

FKM (Viton®) Fluorocarbon: Often called by its DuPont trade name Viton®. Its performance in high temperatures and a broad spectrum of chemical resistance makes fluorocarbon quite a popular choice in many systems with harsh environments. Heat Resistance: Up to 204°C and higher for short periods.

Cold Flexibility: Elasticity retained down to -26°C, some grades down to -46°C

Abrasion resistance: Good

Compression set:
Excellent

Tear resistance:
Fair

Tensile strength:
Very good

Permeability resistance:
Good
(ED Resistant grade FKM provides excellent permeability resistance)

Indefinite shelf life. Inspect after 10 years Aliphatic hydrocarbons (propane, butane, natural gas)

Aromatic and chlorinated hydrocarbons such as benzene, toluene, trichloroethylene and carbon tetrachloride

High vacuum applications

Good ozone, weathering and aging resistance

Glycol based brake fluids (DOT 3 & 4)

Ammonia gas, amines and alkalies

Superheated steam

Low molecular weight organic acids (formic, acetic)

EPDM
Ethylene Propylene Diene Monomer:

EPDM is a terpolymer of ethylene, propylene and a diene component. Its resistance to weathering and aging, glycol brake fluids and many types of strong acids make it a popular choice in chemical and automotive industries
Heat Resistance:Up to 149°C

Cold Flexibility: Elasticity retained down to around -57°C

Abrasion resistance: Very good

Compression set: Very good

Tear resistance:
Very good

Tensile strength:
Very good

Permeability resistance:
Good

Indefinite shelf life.
Inspect after 10 years
Hot water and steam up to 149°C

Glycol based brake fluid (DOT 3 & 4). And silicone based brake fluid (DOT 5)

Many organic and inorganic acids

Cleaning agents, sodium and potassium alkalis

HFD-R fire resistant hydraulic fluids such as Skydrol®

Many polar solvents (alcohols, ketones, esters)

Good ozone, weathering and aging resistance

Mineral oils and grease (severe effect)

Petroleum (gasoline)

Sulphur cured EPDM may cause corrosion when in contact with some metals and alloys (e.g. silver, copper, lead). Use peroxide cured EPDM as an alternative.

CR (Neoprene)
Polychloroprene:
Invented by DuPont scientists in 1930, it is the first synthetic rubber ever produced. Resistance to ammonia and CFC’s make it ideal elastomer for use with refrigerants.
Heat Resistance: Up to around 121°C

Cold Flexibility: Elasticity retained down to around -40°C

Abrasion resistance:
Good

Compression set:
Fair

Tear resistance:
Fair to good

Tensile strength:
Good

Permeability resistance:
Good

15 Years Paraffin based mineral oil with low DPI (e.g. ASTM oil No. 1)

Silicon Oil and grease

Refrigerants

Ammonia

Fair ozone, weathering and aging resistance (compared to NBR)

Aromatic and chlorinated hydrocarbons such as benzene, toluene, trichloroethylene and carbon tetrachloride

Polar solvents such as ketone, acetone, acetic acid and ethylene-ester

VMQ (Silicone)
Methyl Vinyl Silicone:

Silicones have good ozone and weathering resistance. Are good insulators and have physiological neutral properties

Heat Resistance: Up to around 204°C. Some special grades up to 260°C

Cold Flexibility: Elasticity retained down to around -54°C. Some special grades as low as -115°C

Abrasion resistance:
Poor

Compression set:
Very good

Tear resistance:
Poor

Tensile strength:
Poor

Permeability resistance:
Poor

Indefinite shelf life. Inspect after 10 years Animal and vegetable oils and greases

High molecular weight chlorinated hydrocarbons (such as flame-resistant insulators and transformer coolant)

Moderate water resistance

Diluted salt solutions

Good ozone, weathering and aging resistance

Superheated water steam over 121°C

Acids and alkalis

Low molecular weight chlorinated hydrocarbons (trichloroethylene)

Hydrocarbon based fuels and aromatics (benzene, toluene)

Petroleum (gasoline)

TFE/P (Aflas) FEPM
Tetrafluoroethylene-Propylene:

A copolymer of tetrafluoroethylene and propylene, its chemical resistance is excellent across a range of aggressive media

Heat Resistance: Up to around 232°C

Cold Flexibility:
Elasticity retained down to around -9°C

Abrasion resistance: Very good

Compression set: Poor to fair

Tear resistance: Poor to fair

Tensile strength: Fair to good

Permeability resistance: Good

Indefinite shelf life. Inspect after 10 years Bases

Phosphate esters

Amines

Engine oils

Steam and hot water

Pulp and paper liquors

Aromatic and chlorinated hydrocarbons such as benzene, toluene, trichloroethylene and carbon tetrachloride

Polar solvents such as ketone, acetone, acetic acid and ethylene-ester
Petroleum (gasoline)

FFKM
Perfluoroelastomer:
Perflouros offer the highest operating temperature of any elastomer and the broadest spectrum of chemical resistance. Sold under trades names such as Kalrez®, Parafluor®, Chemraz® and Isolast®
Heat Resistance: Up to around 327°C. Depending on grade

Cold Flexibility: Elasticity retained down to around -18°C to -26°C, depending on grade

Abrasion resistance:
Poor

Compression set:
Good

Tear resistance:
Poor to fair

Tensile strength:
Fair to good

Permeability resistance:
Good

Indefinite shelf life. Inspect after 10 years Aliphatic, aromatic and chlorinated hydrocarbons

Chlorinated hydrocarbons

Polar solvents such as ketone, acetone, acetic acid and ethylene-ester

Inorganic and organic acids

Water and steam

High vacuum with minimal loss in weight

Fluorinated refrigerants (R11, 12 ,13, 1134, 114 etc)

Perfluorinated lubricants, PFPE oils and greases like Krytox® and Fomblin®

PUR (PU)
Polyurethane:
Polyurethanes have excellent wear resistance, high tensile strength and high elasticity. There are many different grades of polyurethane o’rings and not all are compatible. Please contact us for more info
Heat Resistance: Up to around 82°C

Cold Flexibility:
Elasticity retained down to around -40°C

Abrasion resistance:
Excellent

Compression set:
Fair

Tear resistance:
Very good

Tensile strength:
Excellent

Permeability resistance:
Good

5 Years Aliphatic hydrocarbons (propane, butane, natural gas)

Mineral and silicone based oils and greases

Polar solvents such as ketone, acetone, acetic acid and ethylene-ester

Glycol based brake fluid (DOT 3 & 4)

Hot water and steam

Alkalis, amines and acids

HNBR
Hydrogenated Nitrile:

A polymer that results from the hydrogenation (treat with hydrogen) of nitrile rubber (NBR). Often used in automotive applications such as air conditioning systems using R134a refrigerant
Heat Resistance: Up to around 150°C

Cold Flexibility:
Elasticity retained down to around -48°C

Abrasion resistance:
Good

Compression set:
Very good

Tear resistance: Fair to good

Tensile strength:
Excellent

Permeability resistance:
Good

15 Years. As per MIL-HDBK-695C Aliphatic hydrocarbons (propane, butane, natural gas)

Animal and vegetable oils and greases

HFA, HFB and HFC hydraulic fluids

Dilute acids, bases and salt solutions at moderate temperatures

Water and steam up to 149°C

Aromatic and chlorinated hydrocarbons such as benzene, toluene, trichloroethylene and carbon tetrachloride

Polar solvents such as ketone, acetone, acetic acid and ethylene-ester

Strong acids

FVMQ
Fluorosilicone:
Possessing similar mechanical and physical properties as VMQ (silicone), FVMQ offers improved low temperature elasticity and better resistance to mineral oils and fuel
Heat Resistance: Up to around 177°C

Cold Flexibility:
Elasticity retained down to around -73°C

Abrasion resistance:
Poor

Compression set:
Good

Tear resistance:
Poor

Tensile strength:
Fair

Permeability resistance:
Poor

Indefinite shelf life. Inspect after 10 years High molecular weight chlorinated hydrocarbons (such as flame-resistant insulators and transformer coolant)

Low molecular weight aromatic hydrocarbons (benzene, toluene)

Aromatic mineral oils

Acids and alkalis

Less hot air resistance than VMQ

Brake fluids, ketones and amines

Other materials

 

XNBR: Carboxylated Nitrile

XNBR is a type of nitrile rubber (NBR) with a carboxylic acid group added to increase mechanical strength and temperature resistance. XNBR exhibits increased tear and abrasion resistance over standard nitrile and is commonly used in dynamic applications as u-cup seals and rod wipers in hydraulic cylinders. XNBR has a similar chemical resistance to NBR.

 

ACM, PA: Polyacrylate

Polyacrylate rubbers are often used in lieu of nitrile in high temperature applications (up to 177°C). ACM offers excellent oil, oxygen, ozone and weathering resistance compared to nitrile, but lack cold flexibility (-15°C) and water compatibility. ACM is often used for rotary shaft seals in automotive applications.

 

AEM, (Vamac): Ethylene Acrylate

A copolymer of ethylene and methyl acrylate with an added carboxylic group, AEM is often used as a higher grade alternative to nitrile (NBR) and is a cost effective alternative to HNBR and ACM in automotive applications, AEM offers resistance to automatic transmission fluid, ozone and oxidising media. Temp range: -29°C to 149°C

 

IRR (Butyl): Isobutylene Isoprene Rubber

Very good resistance to permeability, but seldom used in the seal industry nowadays as NBR provides better mechanical properties and ED resistant FKM (Viton) provides better options for temperature and chemical compatibility. Commonly used for tyre inner-tubes, gas masks, bladders for footballs and a binding agent in C-4 explosive.

 

CSPE, CSM (Hypalon): Chlorosulfonated Polyethylene

Known by its DuPont trade name Hypalon, CSPE offers good permeability resistance and excellent weathering and UV resistance. Has poor to fair compression set characteristics and is rarely used in the sealing industry. It is mainly found in use as a replacement for neoprene in the manufacture of inflatable watercraft, snowshoes, roofing materials and radar domes. Hypalon has been discontinued by DuPont but still available from alternative manufacturers.

 

SBR (Buna-S): Styrene-Butadiene Rubber

Developed as a replacement for natural rubber during World War II, SBR rubber is now one of the most commonly used rubbers worldwide. Uses range from paper coating, loudspeaker damping to chewing gum and building construction. The most common use is SBR blended with natural rubber, butadiene rubber and silica to produce a hard wearing, high friction rubber for automotive tyres and shoe soles. SBR is not commonly used in sealing due to poor weathering, aromatic and oil resistance.

 

Virgin PTFE (Teflon): Polytetrafluoroethylene

Known by its DuPont trade name Teflon. Noted for its broad chemical resistance, low friction coefficient and broad temperature range (upper limit continuous @ 260°C). But being a thermoplastic, it lacks elasticity of an elastomer which can make installation difficult, has very poor compression set characteristics and requires high clamping forces to achieve the same sealing efficiency as a more pliable elastomer.

 

FEP: Fluorinated Ethylene Propylene

Marketed by DuPont as Teflon FEP®, it differs from PTFE by being able to be injection moulded in the manufacturing process. FEP can match PTFE’s chemical resistance and friction coefficient with a broad temperature range between -270°C to 204°C (-454°F to 400°F). FEP o’rings are often called encapsulated o’rings (encaps) because of the two-piece structure of the o’ring; a transparent hollow FEP outer casing with an elastomeric core. This rubber core and FEP jacket gives the o’ring the resistance and friction coefficient of Teflon, but with some elasticity of a rubber o’ring.

 

PFA: Perfluoroalkoxy polymer resin

Often used for extended service in harsh environments, PFA o’rings are basically the same design and construction as encapsulated FEP o’rings, but with an elevated service temperature limit @ 260°C (500°F) and superior resistance to mechanical stresses, especially at high temperatures where FEP can fail.

Note: Encapsulated o’rings like the FEP and PFA above are commonly available with either, an FKM (Viton®), silicone or EPDM rubber core. The most common type having an FKM core. Care should be taken as some chemicals can permeate the outer jacket and come into contact with the elastomeric core, so chemical compatibility and temperature range of the core should also be considered.

 

Metal

Commonly soft alloys like copper, brass or nickel plated steel. For use in extremely harsh environments where temperature and pressures are beyond the capabilities of elastomeric seals. Sometimes used in forced induction race engines to seal engine head to the block; the circular section of the o’ring (sometimes triangular section) creating a high efficiency seal where a normal flat section head gasket alone, would fail.