The most common elastomers are:

Nitrile rubber (NBR)

is a family of unsaturated copolymers of acrylonnitrile (CAN) and butadiene monomers. Although its physical and chemical properties vary depending on the polymer’s composition of nitrile (the more nitrile within the polymer, the higher the resistance to oils but the lower the flexibility of the material), this form of synthetic rubber is generally resistant to oil, fuel, and other chemicals. It is used in the automotive industry to make fuel and oil handling hoses, seals, and grommets. NBR’s ability to withstand a range of temperatures from −40 °C to +108 °C makes it an ideal material for automotive applications. Nitrile rubber is more resistant than natural rubber to oils and acids, but has less strength and flexibility. Nitrile rubber is generally resistant to aliphatic hydrocarbons. Nitrile, like natural rubber, can be attacked by ozone, aromatic hydrocarbons, ketones, esters and aldehydes.

Fluoro rubber (FKM)

Fluoroelastomers are a class of synthetic rubber which provide extraordinary levels of resistance to chemicals, oil and heat, while providing useful service life above 204°C. The outstanding heat stability and excellent oil resistance of these materials are due to the high ratio of fluorine to hydrogen, the strength of the carbon-fluorine bond, and the absence of unsaturation.

The original fluoroelastomer was a copolymer of hexafluoropropylene (HFP) and vinylidene fluoride (VF₂). It was developed by the DuPont Company in 1957 in response to high performance sealing needs in the aerospace industry. To provide even greater thermal stability and solvent resistance, tetrafluoroethylene (TFE) containing fluoroelastomer terpolymers were introduced in 1959 and in the mid to late 1960’s lower viscosity versions of FKMs were introduced A breakthrough in cross linking occurred with the introduction of the bisphenol cure system in the 1970’s. This bisphenol cure system offered much improved heat and compression set resistance with better scorch safety and faster cure speed. In the late 70’s and early 80’s fluoroelastomers with improved low temperature flexibility were introduced by using perfluoromethylvinyl ether (PMVE) in place of HFP..

Fluoroelastomers are a family of fluoropolymer rubbers, not a single entity. Fluoroelastomers can be classified by their fluorine content, 66%, 68%, & 70% respectively. Fluoroelastomers having higher fluorine content have increasing fluids resistance derived from increasing fluorine levels. Peroxide cured fluoroelastomers have inherently better water, steam, and acid resistance.

Fluoroelastomers are used in a wide variety of high-performance applications. FKM provides premium, long-term reliability even in harsh environments. A partial listing of current end use applications (industries like aerospace and automotive) include:

1. O-ring seals in fuels, lubricants and hydraulic systems, Shaft seals, Valve stem seals, Fuel Injector O-rings, Diaphragms, Lathe cut gaskets, cut gaskets.

Silicone (VMQ)

Silicones differ from other polymers in that their backbones consist of Si-O-Si units unlike many other polymers that contain carbon backbones.

Silicone rubber offers good resistance to extreme temperatures, being able to operate normally from -55°C to +300°C. At the extreme temperatures, the tensile strength, elongation, tear strength and compression set can be far superior to conventional rubbers although still low relative to other materials. Organic rubber has a carbon to carbon backbone which can leave them susceptible to ozone, UV, heat and other ageing factors that silicone rubber can withstand well. This makes it one of the elastomers of choice in many extreme environments.

Compared to organic rubbers, however, silicone rubber has a very low tensile strength. For this reason, care is needed in designing products to withstand even low imposed loads.

Ethylene Propylene Rubber (EPDM/EPM)

EPM is a copolymer of ethylene and propylene. This type can only be crosslinked with peroxides. If during the copolymerization of ethylene and propylene, a third monomer, a diene, is added the resulting rubber will have unsaturation and it can then be vulcanized with sulphur. These rubbers are the so-called EPDMs.

The main properties of EPDM are its outstanding heat, ozone and weather resistance. The resistance to polar substances and steam are also good. It has excellent electrical insulating properties.

More materials:

Natural Rubber (NR)

Natural rubber has a very high elasticity, high tensile strength and a very good abrasion resistance. The material is obtained by coagulation of latex derived from the rubber tree? rubber is not resistant to aging and oil. For these reasons NR is rarely used as a seal for technical applications.

Styrene - Butadien Rubber (SBR)

SBR s a synthetic rubber copolymer consisting of styrene and butadiene. It has good abrasion resistance and good aging stability when protected by additives, and is widely used in car tyres, where it is blended with natural rubber.

Like NR it is hardly used for technical applications.

Chloroprene rubber (CR)

Commonly known under the trade name Neoprene® of Dupont.

CR is not characterised by one outstanding property, but its balance of properties is unique among the synthetic elastomers. It has: good mechanical strength, high ozone and weather resistance, good aging resistance, low flammability, good resistance toward chemicals and moderate oil and fuel resistance.

Acrylic rubber (ACM)

Acrylic rubber, known by the chemical name alkyl acrylate copolymer (ACM) or the trade name Hytemp, is a type of rubber that has outstanding resistance to hot oil and oxidation. It has a continuous working temperature of 150 °C and an intermittent limit of 180 °C. Its disadvantages are its low resistance to moisture, acids, and bases. It should not be used in temperatures below −10 °C. It is commonly used in automotive transmissions and hoses.

Hydrogenated Nitrile Butadiene Rubber (HNBR)

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 resistance. 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.

The following table provides a summary of the various elastomer groups and their names according the ISO 1629 standard.

A comparison of the various materials can be found at the chapter “materials – selection table” on our website.