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PROPERTIES OF COMMON
ELASTOMERS
Natural Rubber (NR) (Gum)
As the name would indicate, this elastomer occurs naturally and comes from
the latex of certain trees and plants. After the latex is processed, it
becomes an elastomer with excellent mechanical properties. It has excellent
tensile, elongation, tear resistance and resilience. It has good abrasion
resistance and excellent low temperature flexibility. Without special
additives, it has poor resistance to ozone, oxygen, sunlight and heat. It
has poor resistance to solvents and petroleum products. Useful temperature
range is -67º F to +180º F (-55º C to +82º C).
Nitrile / Buna-N (NBR) (Hycar) (Chemigum)
This is a copolymer of acrylonitrile and butadiene. It has excellent
physical properties, however its claim to fame is based on its resistance to
water, petroleum products and fuels. When compounded properly, it has good
low temperature properties as well as good heat resistance. It does not have
good ozone, oxygen or sunlight resistance without the addition of special
additives. Useful temperature range is -40º F to +275º F (-40º C to +135º
C).
Neoprene / Chloroprene (CR)
This elastomer is made by the polymerization of Chloroprene. It has
excellent physical properties. It is moderately resistant to petroleum
products, sunlight, ozone and heat. It is flame resistant and will not
support combustion. Useful temperature range is -40º F to +275º F (-40º C to
+135º C).
Ethylene-Propylene (EPDM) (EPR)
This is a terpolymer of ethylene, propylene and a diene monomer. It has
outstanding resistance to oxygen, ozone, and sunlight. Its resistance to
polar materials such as phosphate esters, many ketones and alcohol. It has
good electrical properties, low temperature flexibility, excellent heat,
water and steam resistance. Its resistance to petroleum products is poor.
Useful temperature range is -58º F to +300º F (-50º C to +150º C).
Hypalon (CSM)
Hypalon is a chlor-sulfonated polyethylene. It has outstanding oxygen, ozone
and weather resistance. It has excellent resistance to corrosive chemicals
as well as oil and grease. It has excellent abrasion resistance and
excellent tensile and elongation. Useful temperature range is -67º F to
+320º F (-50º C to +160º C).
Styrene Butadiene (SBR) (Buna-S) (GRS)
This is a copolymer of styrene and butadiene. It has similar properties to
natural rubber. Its resistance to solvents and petroleum products is about
the same as natural rubber. Water resistance is better. Without special
additives, it is vulnerable to ozone, oxygen and sunlight.
Useful temperature range is -67º F to +180º F (-55º C to +82º) C).
Silicone
Silicone is made from sand and alkyl or aryl halides. It is predominately
inorganic material. It has outstanding resistance to temperature extremes.
It has excellent vibration damping, and reasonable physical properties such
as tensile and elongation. Tear and abrasion resistance are generally poor.
Useful temperature range is -148º F to +600º F (-100º C to +315º C).
Carboxylated Nitrile (CNBR)
This terpolymer has the excellent water, oil and fuel resistance of
conventional NBR. It has superior abrasion resistance and load bearing
capabilities. It retains good physical properties over a useful temperature
range of -40º F to +300º F (-40º C to +150º C).
Hydrogenated Nitrile (HNBR)
This polymer is produced by complete or partial hydrogenation of NBR. The
result is a polymer with outstanding physical properties. It has good
mechanical properties at elevated temperature. It has excellent resistance
to many chemically aggressive technical oils. Its useful temperature range
is -40º F to +300º F (-40º C to +150º C). |
