Terminology
An A-Z listing of common words used within the rubber industry.
Properties of Rubber
Common name ACRYLIC RUBBER
Chemical name Alkyl acrylate copolymer
Abbreviation ACM
Trade names Hytemp*
The outstanding property of this material is its resistance to hot oil and
to oxidation. It is suitable for continuous use at temperatures up to 150C,
and intermittent exposure up to about 180C. This is provided it is not exposed
to water or moisture - to which it has poor resistance. It is generally
not suitable for use much below -10C and has poor resistance to acids and
bases. It has only modest dynamic properties and rather poor compression
set. Widely used in automotive transmissions and hoses.
Common name BUTADIENE RUBBER
Chemical name Polybutadiene
Abbreviation BR
Trade names
This material has a very low glass transition temperature in the region
-75C to -100C. This results in very low hysterisis and good flexibility
at ambient temperatures and these properties are maintained to temperatures
well below zero. It has high abrasion resistance in severe conditions. Mainly
used in tyres in blends with natural rubber and SBR.
Common name BUTYL RUBBER
Chemical name Isobutylene-isoprene copolymer
Abbreviation IIR
Trade names
This rubber has very high impermeability to gases and is hence used for
the inner tubes of pneumatic tyres, and in vacuum and high pressure applications.
It has an unusually broad loss peak so that, despite having a glass transition
temperature as low as -65C, it displays high damping at ambient temperatures
It has good ozone, weathering, heat, and chemical resistance. Not suitable
for use in contact with mineral oils.
Common name CHLOROBUTYL
Chemical name
Abbreviation CIIR
Trade names
Similar in properties to butyl rubber (qv), but with improved ozone and
environmental resistance and greater stability at high temperatures. Improved
compatibility with other rubber types in blends.
Common name CHLORINATED POLYETHYLENE
Chemical name
Abbreviation CPE
Trade names
Good chemical resistance to hydrocarbon fluids and elevated temperatures.
Used for hose linings. Poor mechanical strength. Mechanical properties may
deteriorate above 100C.
Common name CHLOROSULPHONATED POLYETHYLENE
Chemical name
Abbreviation CSM
Trade names Hypalon*
This is a material with ‘polychloroprene (Neoprene*) plus’ qualities.
It is suitable for continuous use up to about 130C and intermittent use
up to some 30C above this. It has excellent resistance to oxygen, ozone
and most chemicals, including water, but has poor fuel resistance. It has
low gas permeability. It has poor compression set resistance which limits
its usefulness in dynamic sealing applications.
Common name EPICHLORHYDRIN
Chemical name
Abbreviation CO
Trade names
High resistance to ageing, oxidation, ozone, and hot oil. Good resistance
to hydrocarbon solvents, moderate low temperature flexibility. Poor abrasion
resistance and electrical properties.
Common name ETHYLENE ACRYLIC
Chemical name
Abbreviation AEM
Trade names Vamac*
This has better low temperature performance (to -40C) and dynamic properties
than acrylic (qv), but at the expense of fluid resistance. It has good compression
set resistance, but poor resistance to aromatic hydrocarbons, strong acids
and bases.
Common name ETHYLENE PROPYLENE RUBBER
Chemical name Ethylene propylene copolymer, or a terpolymer with a diene
Abbreviation EPM, EPDM
Trade names Dutral*, Nordel*, Vistalon*
Probably the most water resistant rubber available, and this resistance
is maintained to high temperatures (up to 180C in steam for peroxide cures).
The highest temperature resistance is achieved by using peroxide cured grades.
Has excellent resistance to atmospheric ageing, oxygen and ozone up to about
150C. It has good resistance to most water-based chemicals and to vegetable-based
hydraulic oils. However, it has very poor resistance to mineral oils and
di-ester based lubricants.
Common name FLUOROELASTOMERS
Chemical name
Abbreviation FKM
Trade names Dai-El*, Fluorel*, Technoflon*, Viton*
This is a family of rubbers designed for very high temperature operation.
They can operate continuously somewhat in excess of 200C depending on the
grade, and intermittently to temperatures as high as 300C. They have outstanding
resistance to chemical attack by oxidation, by acids and by fuels. They
have good oil resistance. However, at the high operating temperatures they
are weak, so that any design must provide adequate support against applied
forces. They have limited resistance to steam, hot water, methanol, and
other highly polar fluids. They are attacked by amines, strong alkalis and
many Freons. There are standard and special grades - the latter can be designed
to have special properties such as improved low-temperature resistance.
Common name HYDROGENATED NITRILE RUBBER
Chemical name
Abbreviation HNBR
Trade names Therban*, Tornac*, Zetpol*
The properties of hydrogenated nitrile rubber depend on the acrylonitrile
(ACN) content, and on the degree of hydrogenation. They can be ‘tailored’
to particular applications, but have the general advantage over standard
nitrile rubber of having higher temperature resistance and higher strength.
They have good high temperature oil and chemical resistance and are resistant
to amines. They are suitable for use in methanol and methanol/hydrocarbon
mixtures if the correct ACN level is selected. They have good resistance
to hot water and steam. They can have excellent mechanical properties including
strength, elongation, and tear. Also, abrasion resistance, compression set,
and extrusion resistance. For the best properties peroxide curing is used,
unless low hysteresis is required. They are reported to be satisfactory
up to temperatures around 180C in oil. Fully saturated grades have excellent
ozone resistance. They have poor resistance to some oxygenated solvents
and aromatic hydrocarbons.
Common name NATURAL RUBBER
Chemical name cis-polyisoprene
Abbreviation NR
Trade names
The outstanding strength of natural rubber has maintained its position as
the preferred material in many engineering applications. It has a long fatigue
life and high strength even without reinforcing fillers. Other than for
thin sections it can be used to approximately 100C, and sometimes above.
It can maintain flexibility down to -60C if compounded for the purpose.
It has good creep and stress relaxation resistance and is low cost. Its
chief disadvantage is its poor oil resistance and its lack of resistance
to oxygen and ozone, although these latter disadvantages can be ameliorated
by chemical protection.
Common name NITRILE RUBBER
Chemical name acrylonitrile-butadiene copolymer
Abbreviation NBR
Trade names Breon*, Chemigum*, Europrene*, Hycar*, Krynac*, Nipol*
At temperatures up to 100C, or with special compounding up to 120C, nitrile
rubber provides an economic material having a high resistance to aliphatic
hydrocarbon oils and fuels. Different grades are available - the higher
the acrylonitrile (ACN) content, the higher the oil resistance but the poorer
is the low temperature flexibility. It has high resilience and high wear
resistance but only moderate strength. It has limited weathering resistance,
and poor aromatic oil resistance. It can generally be used down to about
-30C, but special grades can operate at lower temperatures.
Common name PERFLUORO ELASTOMERS
Chemical name
Abbreviation FFKM
Trade names Chemraz*, Kalrez*, Perfluor*, Simriz*, Zalak*
These are materials having even greater heat and chemical resistance than
the fluoroelastomers. They can be used in extreme conditions up to temperatures
around 300C or even higher with special compounding. Their disadvantages
are difficult processing, very high cost, poor physical properties at high
temperature, and their high glass transition temperatures which limit their
use at low temperatures. Most materials cannot be used below zero Celsius,
and even at normal ambient temperatures their creep properties are likely
to be poor.
Common name POLYCHLOROPRENE
Chemical name
Abbreviation CR
Trade names Neoprene*
This rubber has a generally good balance of mechanical properties and fatigue
resistance second only to natural rubber, but with superior chemical, oil,
and heat resistance. It is widely used in general engineering applications.
It is less resistant than natural rubber to low temperature stiffening but
can be compounded to give improved low temperature resistance. It has good
ozone resistance. It is suitable for use with mineral oils and greases and
dilute acids and alkalis, but is unsuitable in contact with fuels. It has
generally poorer set and creep than natural rubber.
Common name POLYNORBORNENE RUBBER
Chemical name
Abbreviation PNB
Trade names Norsorex*
This rubber is generally used for specialist applications where a very soft
material is required. Materials can be produced in the range 15 - 25 IRHD
with good damping properties, which is more like a jelly than a conventional
rubber. It is therefore used for vibration absorption. It is not oil resistant
and has an upper temperature limit of around 70C.
Common name POLYSULPHIDE RUBBER
Chemical name
Abbreviation TR
Trade names Thiokol*
Very good resistance to oils, fuels, solvents, oxygen, and ozone. Impermeable
to gases. Poor mechanical properties and poor heat resistance.
Common name POLYURETHANE RUBBER
Chemical name
Abbreviation AU (polyester) EU (polyether)
Trade names Adiprene*, Estane*, Genthane*
These materials have high tear strength and good wear resistance. Their
upper temperature limit is typically 80C. They have excellent resistance
to weathering and oxidation. They resist hydrocarbon fuels and mineral oils
but some grades hydrolyse in hot water. They are one of the best rubbers
for abrasion resistance and are therefore used in reciprocating seals. Some
grades are castable.
Common name SILICONE (and FLUOROSILICONE) RUBBER
Chemical name
Abbreviation MQ (methyl groups on chain)
VMQ (methyl and vinyl groups)
PMQ (methyl and phenyl groups)
FMQ (methyl and fluorine groups)
Trade names Silastic*
The outstanding property of these materials is their very wide temperature
range. Typically the range is -60C to 200C and above, with PMQ down to -90C.
They do not have very good physical properties, but the properties they
do have are retained to high temperatures. FMQ has better oil and water
resistance than the others. They are used in room temperature vulcanizing
(RTV) sealants for joints. Beware corrosion if acetic acid is present as
a curing agent.
Common name STYRENE BUTADIENE RUBBER
Chemical name
Abbreviation SBR
Trade names
This is the highest volume general purpose synthetic rubber. It is very
weak unless reinforcing fillers are incorporated. With suitable fillers
it is a strong rubber although not approaching natural rubber or polychloroprene.
Otherwise it has similar chemical and physical properties to natural rubber,
with generally better abrasion resistance but poorer fatigue resistance.
Common name TETRA-FLUOROETHYLENE/PROPYLENE
Chemical name
Abbreviation FEPM
Trade names Aflas*
This is a high temperature polymer capable of operating in the range 20C
to 200C (to 260C in steam). It has good overall chemical resistance including
amines, methanol, steam and hot water. Its hydrocarbon resistance approaches
that of FKM copolymer. It has, however, poor compression set and a high
minimum working temperature
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