ACM – acrylate rubber

ACM is used mainly by the automotive industry as it is resistant to engine, transmission and ATF oils even at high temperatures. The temperature application range is from –20°C to +150°C.

AEM – ethylen acrylate rubber

trade name e.g. Vamac® (Du Pont-Dow Elastomers)

AEM is like ACM mainly used by the automotive industry. AEM has a higher resistance to low and high temperature than ACM and based on its entire properties can be classified between ACM and FKM. The material is resistant to weathering and ozone and can be used with enriched mineral oils, water and refrigerants. The temperature application range is from –30°C to +150°C (for a short time +175°C).

AU – polyester urethane
EU – polyether urethane

trade name e.g Desmopan® (Bayer)

Polyurethanes differ from classic elastomers in that they have much higher mechanical properties for example a high resistance to abrasion, wear and extrusion, a high tensile strength and tear resistance. The material is resistant to ageing and ozone, and can be used with mineral oils and greases, silicone oils and greases, non-inflammeble fluids HFA and HFB and water up to of 50°C, as well as pure aliphatic hydrocarbons.

CR – chloroprene rubber

trade name e.g. Neoprene® (Du Pont-Dow Elastomers)

Chloroprenes have excellent resistance to ozone, ageing and weathering and also good mechanical properties. They have average resistance to mineral oils, and are suitable for use with many refrigerants. The temperature application range is from –40°C to +100°C.

EPDM – ethylene propylene diene rubber

trade name e.g. Nordel®‚ (Du Pont-Dow Elastomers)

EPDM materials generally have a high resistance to hot water, steam, ageing and chemicals, and are suitable for a wide range of temperature applications. They are divided into sulphur- and peroxide-cured types. Peroxide-cured compounds are suitable for higher temperature ranges and have a much lower compression set.

EPDM has a good resistance to hot water and steam, detergents, caustic potash solutions, sodium hydroxide solutions, silicone oil and greases, many polar solvents, many diluted acids and chemicals. Special qualities are recommended for glycol-based brake fluids. EPDM materials are totally unsuitable for use with all mineral oil products (lubricants, fuels). They can be used between –45°C and +130°C (peroxide-cured –50°C to +150°C).

FEP covered O-rings

FEP – fluorinated ­ethylene-propylene

FEP is a thermoplastic material with similar properties to PTFE. Seamless FEP-encapsulated O-rings have an elastic core in FPM or VMQ. They are used at very high thermal and chemical loads. The extremely high chemical resistance of the cover protects the elastic core material against the chosen medium. Another advantage of the cover is its very low coefficient of friction.

This results in a combination of very high chemical and thermal load bearing ability and the elastic properties of standard commercial elastomers. The core material is chosen to suit the temperature range and medium.

Because of its limited flexibility, great care is required during installation. Warming the material in water or oil to between approx. 80°C and 100°C increases flexibility and supports the installation.

Depending on the core material, the temperature application range is from –55°C to +200°C.

FFKM – perfluoro rubber

trade name e.g. Kalrez® (Du Pont-Dow Elastomers)

The chemical and heat resistance of perfluoro elastomers are similar to those of PTFE. They combine the positive properties of PTFE with the elastic behaviour of FKM. Because this material group is considerably more expensive, perfluoro elastomers are only used if other materials cannot meet the specifications and if safety requirements justify the higher expenditure.

Typical applications for perfluoro elastomers include the chemical, oil and semi conductor industries, high vacuum technology, and the aerospace industry.

FVMQ – fluorosilicone rubber

trade name e.g. Silastic LS® (Dow Corning)

Although fluorosilicone elastomers have the same mechanical properties as silicone, they are far more resistant to oils and fuels. The temperature range of applications is somewhat more restricted than that of silicone. The temperature application range is from –55°C to +175°C.

HG – hard fabric materials

HG hard fabric materials are produced from various fabric/resin combinations, such as synthetic fibre fabric + phenolic resin, cotton fabric + phenolic resin or polyester fabric + polyester resin. HG materials are selected for application areas in hydraulics with high loads and shear forces. With the selection of the optimal material combinations (fabric/resin) a long product life, high restoring force, low friction (dry-running characteristics exist) and very high contact pressure (load capacity) can be achieved. Dichtomatik’s standard material displays no moisture expansion in water; or measurable absorption of water.

HNBR – hydrogenated acrylonitrile-butadiene rubber

trade name e.g. Therban® (Bayer)

HNBR is obtained by fully or partially hydrogenating NBR. It leads to considerable improvement in resistance to heat, ozone and ageing, and gives it very good mechanical properties, e.g. good resistance to wear. The media resistance compares to that of NBR. HNBR has a good resistance to some refrigerants. The temperature application range is from -30°C to +150°C.

NBR - acrylonitrile-butadiene rubber

trade name e.g. Perbunan® (Bayer)

NBR is the most common standard material because of its good mechanical properties and resistance to mineral oil-based lubricants and greases. Good resistance to fuels is usually possible only with special compounds.

Its properties are mainly determined by the acrylonitrile content (ACN between 18% and 50%). A low ACN content ensures good flexibility at low temperatures, but offers limited resistance to oils and fuels; as the ACN content increases, flexibility at low temperatures decreases and resistance to oils and fuels improves.The standard NBR material offers an average ACN content to suit a wide range of applications with balanced properties. It has good mechanical technological values such as high abrasion resistance, as well as good resistance to mineral oil-based lubricants and greases, hydraulic oils H, H-L, H-LP, non-inflammable hydraulic fluids HFA, HFB, HFC, aliphatic hydrocarbons, silicone oil and greases and water to approx. +80°C.

NBR is generally not resistant to aromatic and chlorinated hydrocarbons, fuels with a high aromatic content, polar solvents, glycol-based brake fluids, and non-inflammable hydraulic fluids HFD. It has a low resistance to ozone, weather and ageing, but in most applications, e.g. when the material is wetted with oil, this has no negative effect.

NBR F – rubber fabric materials

Cotton or synthetic fibre fabric can be used as the basis for rubber fabric materials. The standard material for hydraulic seals at Dichtomatik is cotton fabric. In addition to the standard material, a whole range of other fabric types and almost all elastomers for impregnation are available. For the production of hydraulic seals, the fabric is impregnated with an NBR elastomer solvent. Subsequently, appropriate dimensions are cut out of the impregnated cloth and rolled for further processing and then vulcanised in a vulcanisation press, under the influence of temperature and time, to produce hydraulic seals. Hydraulic seals are either produced totally of rubber fabric material or segments of the elastomer part are reinforced with fabric, e.g. the running surface or the side facing away from the pressure, to achieve better protection from gap extrusion. The so called multi component seal can be produced by vulcanising pure elastomer onto the seal.