This section explains the uses and compatibilities of elastomers commonly used by Emerson Process Management Regulator Technologies.

Elastomers: Chemical Names and Uses

NBR - Nitrile Rubber, also called Buna-N, is a copolymer of butadiene and acrylonitrile. Nitrile is recommended for: general purpose sealing, petroleum oils and fluids, water, silicone greases and oils, diester based lubricants (such as MIL-L-7808), and ethylene glycol based fluids (Hydrolubes). It is not recommended for: halogenated hydrocarbons, nitro hydrocarbons (such as nitrobenzene and aniline), phosphate ester hydraulic fluids (Skydrol, Cellulube, Pydraul), ketones (MEK, acetone), strong acids, ozone, and automotive brake fluid. Its temperature range is - 60° ; to +225°F (-51° to +107°C), although this would involve more than one compound.

EPDM, EPM - Ethylenepropylene rubber is an elastomer prepared from ethylene and propylene monomers. EPM is a copolymer of ethylene and propylene, while EPDM contains a small amount of a third monomer (a diene) to aid in the curing process. EP is recommended for: phosphate ester based hydraulic fluids, steam to 400°F (204°C), water, silicone oils and greases, dilute acids, dilute alkalis, ketones, alcohols, and automotive brake fluids. It is not recommended for: petroleum oils, and diester based lubricants. Its temperature range is -60° to +500°F (-51° to +260°C) (The high limit would make use of a special high temperature formulation developed for geothermal applications).

FKM - This is a fluoroelastomer of the polymethylene type having substituent fluoro and perfluoroalkyl or perfluoroalkoxy groups on the polymer chain. Viton® and Fluorel are the most common trade names. FKM is recommended for: petroleum oils, diester based lubricants, silicate ester based lubricants (such as MLO 8200, MLO 8515, OS-45), silicone fluids and greases, halogenated hydrocarbons, selected phosphate ester fluids, and some acids. It is not recommended for: ketones, Skydrol 500, amines (UDMH), anhydrous ammonia, low molecular weight esters and ethers, and hot hydrofluoric and chlorosulfonic acids. Its temperature range is -20° to +450°F (-29° to +232°C) (Limited use at each end of the temperature range).

CR - This is chloroprene, commonly know as neoprene, which is a homopolymer of chloroprene (chlorobutadiene). CR is recommended for: refrigerants (Freons, ammonia), high aniline point petroleum oils, mild acids, and silicate ester fluids. It is not recommended for: phosphate ester fluids and ketones. Its temperature range is -60° to +200°F (-51° to +93°C), although this would involve more than one compound.

NR - This is natural rubber which is a natural polyisoprene, primarily from the tree, Hevea Brasiliensis. The synthetics have all but completely replaced natural rubber for seal use. NR is recommended for automotive brake fluid, and it is not recommended for petroleum products. Its temperature range is -80° to +180°F (-62° to +82°C).

FXM - This is a copolymer of tetrafluoroethylene and propylene; hence, it is sometimes called TFE/P rubber. Common trade names are Aflas (3M Co.) and Fluoraz (Greene, Tweed & Co.). It is generally used where resistance to both hydrocarbons and hot water are required. Its temperature range is +20° to +400°F (-7° to +204°C).

ECO - This is commonly called Hydrin rubber, although that is a trade name for a series of rubber materials by B.F. Goodrich. CO is the designation for the homopolymer of epichlorohydrin, ECO is the designation for a copolymer of ethylene oxide and chloromethyl oxirane (epichlorohydrin copolymer), and ETER is the designation for the terpolymer of epichlorohydrin, ethylene oxide, and an unsaturated monomer. All the epichlorohydrin rubbers exhibit better heat resistance than nitrile rubbers, but corrosion with aluminum may limit applications. Typical operating temperature ranges are -20° to +325°F (-29° to +163°C) for the CO and -55° to +300°F (-48° to +149°C) for the ECO and ETER elastomers.

FFKM - This is a perfluoroelastomer generally better known as Kalrez (DuPont) and Chemraz (Greene, Tweed). Perfluoro rubbers of the polymethylene type have all substituent groups on the polymer chain of fluoro, perfluoroalkyl, or perfluoroalkoxy groups. The resulting polymer has superior chemical resistance and heat temperature resistance. This elastomer is extremely expensive and should be used only when all else fails. Its temperature range is 0° to +500°F (-18° to +260°C). Some materials, such as Kalrez 4079 can be used to 600°F (316°C).

FVMQ - This is fluorosilicone rubber which is an elastomer that should be used for static seals because it has poor mechanical properties. It has good low and high temperature resistance and is reasonably resistant to oils and fuels because of its fluorination. Because of the cost, it only finds specialty use. Its temperature range is -80° to +350°F (-62° to +177°C).

VMQ - This is the most general term for silicone rubber. Silicone rubber can be designated MQ, PMQ, and PVMQ, where the Q designates any rubber with silicon and oxygen in the polymer chain, and M, P, and V represent methyl, phenyl, and vinyl substituent groups on the polymer chain. This elastomer is used only for static seals due to its poor mechanical properties. Its temperature range is -65° to +450°F (-54° to +232°C).