Elastomers

Elastomers, or rubber materials, are polymers that are chemically cross-linked through the vulcanization process. Because of these chemical bonds, they do not melt but begin to decompose at high temperatures.

Nitrile butadiene rubber

Nitrile butadiene rubber (NBR) is a family of synthetic rubber copolymers of acrylonitrile and butadiene. Although its physical and chemical properties vary according to the nitrile content of the polymer, these rubbers are generally resistant to oil, fuel and other chemicals.

SKF Ecorubber-1

SKF Ecorubber-1 is an elastomer based on acrylonitrile-butadiene rubber (NBR), used for U-cups, packing, special seals and various components. This material has good resistance to mineral oils, greases and HFA, HFB and HFC pressure fluids. However, it is not resistant to glycol-based fluids, HFD fluids, aromatic fluids such as benzene, esters, ketones and amines, or concentrated acids and bases.

Nitrile rubber (R)

The term nitrile rubber is used for acrylonitrile-butadiene rubber (NBR). This material has very good engineering properties and is a general-purpose sealing-lip material. It is a copolymer produced from acrylonitrile and butadiene and provides good resistance to the following media:

• Most mineral oils and mineral-oil-based greases
• Common fuels such as petrol, diesel fuel and light heating oils
• Animal and vegetable oils, fats and hot water

Nitrile rubber also tolerates short periods of dry running at the sealing lip. The permissible operating temperature range for nitrile rubber is -40 to +100 °C (-40 to +210 °F). Temperatures up to 120 °C (250 °F) can be tolerated for short periods.

SKF also offers a special nitrile rubber with a temperature range between -55 and +110 °C (-65 and +230 °F

FKM

FKM (or FPM according to ISO) elastomers are based on fluororubber and have exceptional resistance to heat, weathering and many other chemicals.

SKF Ecorubber-2

SKF Ecorubber-2 is a fluororubber-based elastomer (FPM, FKM) that can be used for U-cups, lip seals, packing, wipers and special seals. Its outstanding properties include high resistance to heat, ozone, many chemicals and weathering. SKF Ecorubber-2 is compatible with mineral oils and greases containing sulphur, HFD pressure fluids (almost all phosphate esters and chlorinated hydrocarbons), crude oil and sour gas. SKF Ecorubber-2 is not resistant to anhydrous ammonia, amines, ketones, esters, hot water or low-molecular-weight organic acids.

SKF Duralife (V)

The SKF Duralife fluororubber (FKM) compound, formerly called LongLife, was developed by SKF and is characterized by very good wear, thermal and chemical resistance. Its resistance to weathering and ageing caused by UV light and ozone is also very good, and its gas permeability is very low.

SKF Duralife also provides exceptional properties under severe environmental conditions and can withstand operating temperatures up to 200 °C (390 °F). The material is also resistant to oils and hydraulic fluids, fuels and lubricants, mineral acids and aliphatic as well as aromatic hydrocarbons that could cause many other sealing materials to deteriorate. SKF Duralife seals can also tolerate short periods of dry running at the lip. The seals should not be used in the presence of esters, ethers, ketones, certain amines and hot anhydrous hydrofluorides. Because of the compound's valuable properties, SKF manufactures seals with SKF Duralife sealing lips for all common shaft diameters.

EPDM

EPDM rubber (ethylene propylene diene monomer, M-class), a type of synthetic rubber, is a group of elastomers with exceptional resistance to heat, ozone, weathering, hot water, steam, detergents and polar organic solvents.

SKF Ecorubber-3

SKF Ecorubber-3 is an elastomer based on ethylene-propylene-diene rubber (EPDM) that can be used for U-cups, lip seals and packing. SKF Ecorubber-3 has exceptional resistance to hot water, steam, detergents and polar organic solvents. SKF Ecorubber-3 is not resistant to mineral oil and other non-polar media. Resistance to weathering, ozone and ageing is good. When used in glycol-based brake fluids, national regulations must be observed.

HNBR

Hydrogenated nitrile butadiene rubbers are saturated copolymers of acrylonitrile and butadiene suitable for use with aliphatic hydrocarbons and mineral oils. Their physical and chemical properties vary depending on polymer composition.

SKF Ecorubber-H

SKF Ecorubber-H is a hydrogenated or saturated acrylonitrile-butadiene rubber (H-NBR) suitable for use at higher operating temperatures in aliphatic hydrocarbons such as propane or butane, mineral oils, greases and sulphurous crude oil. It can also be used in many diluted acids, bases, salt solutions and glycol-water mixtures. SKF Ecorubber-H is not compatible with fuels containing high levels of aromatic hydrocarbons (premium petrol blends), benzene-containing fuels (petrol/alcohol blends), ketones, esters, ethers or chlorinated hydrocarbons such as trichloroethylene and tetrachloroethylene.

SKF Duratemp (H)

SKF Duratemp is a hydrogenated nitrile rubber (HNBR) developed by SKF that combines the wear resistance of SKF Duralip with increased resistance to high temperatures, as shown in diagram 1. SKF Duratemp is also more resistant to chemical attack, weathering, ageing and ozone. However, oil-in-air mixtures can have a negative effect. The upper operating temperature limit is 150 °C (300 °F), which is significantly higher than that of standard nitrile rubber. SKF Duratemp is used mainly for heavy-duty industrial seals or where extended service life is required.

Silicone rubber

Silicone rubbers (MVQ or VMQ) are characterized by high heat, weathering and ageing resistance. Silicone rubbers are mainly used for static or quasi-static applications and should not be exposed to dry running.

SKF Ecosil

SKF Ecosil is a silicone rubber (MVQ) that can be used for O-rings, seals and special seals. Because of its relatively poor mechanical properties compared with other rubbers, SKF Ecosil is used mainly for static applications. It is highly resistant to weathering, ozone and ageing. Compatibility with mineral oils depends on the aromatic hydrocarbon content of the oil.

XNBR

Carboxylated nitrile rubbers (XNBR) are enhanced NBR grades that combine the engineering properties of nitrile rubber (NBR) with increased wear resistance. They are used mainly for heavy-duty industrial seals.

SKF Duralip (D)

SKF Duralip is a carboxylated nitrile rubber (XNBR) developed by SKF that combines the good engineering properties of nitrile rubber with increased wear resistance, as shown in diagram 1. It is used mainly for heavy-duty industrial seals. Seals made from this material should be selected where abrasive contaminants such as sand, soil and rocks can reach the seal on the shaft.

Polyacrylate elastomer

Polyacrylate elastomers are more heat resistant than nitrile rubber or SKF Duralip. The operating temperature range for polyacrylate elastomers is between -40 and +150 °C (-40 and +300 °F), and in some fluids the upper limit can be extended to 175 °C (345 °F). Polyacrylate seals are resistant to ageing and ozone and are also suitable for lubricants containing EP additives. They should not be used to seal water, acids or alkalis, etc. Dry running should be avoided.