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Rubber Selection - A Guide to Outline
Properties
The information below is intended to give a broad overview
of the properties of a number of different rubbers. This is
intended to aid in the selection of rubbers for particular
service conditions. A guide of this sort is only intended as a
first step in selection - mainly to eliminate materials which
are obviously unsuitable. Beyond this, factors such as
component size can have a major influence on properties such
as oxidation resistance and oil resistance. Also, the
properties of a vulcanized rubber can be significantly
influenced by details of the compounding. Practical materials
will have, in addition to the base polymer, fillers,
anti-degradants, crosslinking agents, accelerators etc. All of
these can have an influence on the physical and chemical
stability of the finished material. In critical applications
it is therefore advisable to give considerable thought, or
take advice, on the formulation of the compound. As the
potential for 'tailoring' compound to specific applications is
essentially limitless, it is often advisable to carry out
preliminary qualification tests to ensure that the compound
chosen will perform as intended.
Trade names are given
to assist in recognition, but the list is necessarily only
partial, and is given in alphabetical order. Trade names are
generally registered and/or copyright and are indicated by an
asterisk after the name - see below.
Abbreviations used
are those based on latest ISO recommendations.
The
temperature ranges quoted are only a rough guide, because the
temperature range possible will depend upon the particular
application, and may depend on detailed differences between
alternative versions of the same rubber. In some cases greater
extremes of temperature can be tolerated than indicated
below.
The information given below is given in good
faith, but MERL can accept no responsibility for the
information. Normal screening procedures should be operated
before any material is selected for service.
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Rubber Types
| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| Common name |
CHLOROSULPHONATED POLYETHYLENE |
| Chemical name |
|
| Abbreviation |
CSM |
| Trade names |
Hypalon® |
| This is a material with Neoprene
polychloroprene '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.
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| 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.
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list |
| 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.
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list |
| 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.
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| 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.
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| 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.
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| Common name |
ISOPRENE RUBBER |
| Chemical name |
Synthetic cis-polyisoprene |
| Abbreviation |
IR |
| Trade names |
Natsyn* |
| This is the same polymer as natural rubber
- but made synthetically. Essentially similar in
properties to natural rubber (qv) it may be somewhat
weaker because it is not 100% the cis isomer.
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| 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.
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list |
| 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.
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| 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.
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| Common name |
POLYCHLOROPRENE |
| Chemical name |
|
| Abbreviation |
CR |
| Trade names |
Neoprene polychlorprene |
| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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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|
Hypalon®, Nordel®, Viton®,
Kalrez® and Neoprene polychlorprene are all registered
trademarks of DuPont Dow
Elastomers | | |
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