Elastomers Elastomers are polymeric materials that have high elasticity, stretch double, and when the force causing stretch releases, elastomers return to the first status pretty much.
These materials called “Rubber” acquire a chemical reaction (cross-linking reaction, in other words “vulcanization”).
Rubbers, which has crosslinking property but they are not, are polymers can vulcanize. These materials that can be shaped in specific duration under temperature and pressure show liquid and flexible property.
Elastomeric materials provide real dynamic and static impermeability in sealing elements From this point, choosing the right elastomer is very important according to application.
Below you can find general information about basic elastomers
NBR (acrylonitrile butadiene rubber) is a synthetic rubber, which is a known resistance to oil and fuels.
With increasing nitrile content, its resistance to petroleum-based oils and hydrocarbons increases, but its elasticity at low temperature falls. It swells limited quantity in fuels, but even this swelling situation doesn’t affect physical properties. It has good resistance to oils and greases. With reinforcing proper additives, its resistance to ozone and other air factors can be increased even more. Despite its high polarity water has a limited impact on NBR.
It is a basic elastomer using for dynamic and static sealing applications including oil seals, hydraulic and pneumatic seals and o-rings.
Proper using temperature range is from -30°C up to +105°C. It can be used up to +130°C for short periods.
ACM(polyacrylate rubber) ) is a synthetic elastomeric material that is most commonly used working in hot oil.
It demonstrates excellent resistance to active oils, oxidation and weathering. And it performs well in petroleum-based hydraulic oils, high-pressure oils, hypoid oils, greases and fluids with EP.
It is not convenient in dry conditions and water. Low temperature performance is also weak. Shaft motion tracing capability is worse than NBR.
Proper using temperature range is from -25°C up to +150°C.
AEM is in the same family with ACM, contains ethylene and it is more resistant than ACM to high temperature. İt positions between ACM and FKM (Fluorocarbon) in consideration of its specifications.
It shows good swelling resistance to motor oils, paraffin, water and freezers. But has bad resistance to aromatics, brake oils and acids.
Proper using temperature range is from -40°C up to +160°C.
FKM (Fluorocarbon rubber) known as trade name Viton® is an elastomer, that is preferred in environments with high temperatures, rich with ozone and corrosive chemicals.
It exhibits good resistance to aliphatic and aromatic hydrocarbons, jet engine oils, greases, motor oils, gasoline and corrosive fluids. Dry air resists higher working temperatures than usual. It is well-suited for rotary shaft applications at high rotations. But it is hardly preferred in food and drug industries. FKM is a relatively expensive rubber.
Proper using temperature range is from -30°C up to +225°C.
The most renowned characteristic of VMQ (vinyl-methyl silicone) rubber is excellent resistance to heat and the wide temperature range it can operate within.
However, its mechanical properties are not strong in general. VMQ has very good dielectric strength. And also it has good resistance to weathering, ozone and humidity. It can work in hot water. it has good resistance to oils, but not recommended for hydrocarbon and steamy environments.
Specific variations are particularly preferred by the food and drug industries.
Proper using temperature range is from -60°C up to +200°C. Special variations are available to resist up to +300°C, in special applications.
HNBR (hydrogenated nitrile rubber) nis a polymer that can be produced from conventional NBR polymer by hydrogenation of the unsaturated bonds of some part or all in the butadiene.
This elastomer has similar resistance to chemicals with NBR. HNBR vulcanizing with peroxide cure can operate at high temperatures. It is preferred for reciprocating and mobile hydraulic applications in automotive industries.
Using temperature range is from -30°C up to +150°C.
EPDM (Ethylene propylene diene rubber) ) has the widest use in the industry.
It is suitable to use in phosphate ester based non-flammable hydraulic fluids, hot water and steam, some weak acids, alkalis and ketones.
EPDM shows excellent resistance to heat, water, steam, ozone, sunlight and weathering. But it is not convenient used in mineral oils, aromatic compounds and petroleum products.
Proper using temperature range is from -50°C up to +150°C.
SBR (styrene butadiene rubber) ) is the most common type of synthetic rubber and has the widest use instead of natural rubber in the industry today.
Characteristics resemble those of natural rubber. The material exhibits very goods elasticity and abrasion resistance. Hardness increases with styrene content, and elasticity improves with increasing butadiene. Dynamic fatigue performance is inferior to natural rubber.
It is well used in castor-based hydraulic fluids.
Proper using temperature range is from -50°C up to +100°C.
CR (Chloroprene rubber) as a synthetic rubber has very good resistance to weathering and ozone. It has strong mechanical properties and anti-aging characteristics.
It is resistant to swelling in most kinds of oil. Because of the compound of chlorine, it has the good flame-retardant capability.
A good balance of properties allows various uses of this rubber including the production of belts, hoses, glands, adhesives and engineering applications.
Proper using temperature range is from -45°C up to +100°C.
NR (natural rubber) ) is the oldest rubber historically. Latex produced in rubber plantations is treated in a series of processes to obtain natural rubber.
It has very high elasticity and good abrasion resistance.
And it shows good resistance to oils in automotive brake fluids and castor-based hydraulic fluids. NR shows fine strength characteristics at low temperatures but fails to resist some oils, ozone and environments at high temperatures.
Proper using temperature range is from -60°C up to +90°C.
The most characteristic advantages of PU(polyurethane) , are high tensile strength and abrasion resistance. Variations of ester (AU) and ether based are common. Variation of thermoplastic is known as TPU.
It also shows good resistance to the effects of weathering, ozone and oxidation. PU is suitable for use in petroleum-based oils and hydrocarbon-based fuels. But it is weak to acid, base, ketone, water or steam.
Polyether-based variation (EU) is more resistant to water. It is preferred especially in high friction environments. Polyurethane rubber is used frequently in hydraulic and pneumatic sealing applications like reciprocating pistons or wipers.
Proper using temperature range is from -30°C up to +100°C.