EPDM gaskets

What is EPDM?

EPDM is the abbreviation for ethylene-propylene-diene(monomer) rubber and belongs to the M-group of rubbers. Within the framework of the classification of rubbers, seals made of this sealing material are thus assigned to the non-polar saturated rubbers. The material is a high-quality, rubber-elastic, synthetic elastomer made of very long, saturated and highly stable molecular chains, the macromolecules ethylene, propylene and diene. Other trade names are, for example, BUNA-AP®, KELTAN® and NORDEL®. Due to the diverse properties and resistances of EPDM, the sealing material can be used in many areas of application.

Depending on the intended use or area of application, we have a wide range of different EPDM sealing materials available as the base material for our EPDM seals. These materials differ not only in color but also in terms of their chemical, thermal, and mechanical properties.

In addition to our standard qualities, we also manufacture EPDM seals from EPDM sealing materials for special requirements, for which the relevant conformities and approvals are available. This means we can produce EPDM seals with a fire protection classification or for contact with drinking water.

We source most of our EPDM sealing material from the Austrian manufacturer Semperit. We are their largest distributor in the elastomer sheet sector. Thanks to Semperit, as a European manufacturer, we can supply you with high-quality EPDM seals of consistent quality that are characterized by their durability and precision. Sustainability and good traceability of materials are also hallmarks of the company.

All Semperit EPDM grades are free of halogens and conflict materials. They also comply with REACH and RoHS. In addition to Semperit grades, the material is also available in imported quality and Holcim quality. In the field offoamed materialsin combination with EPDM components, we carrycellular rubberandfoam rubber.

The properties of EPDM as a sealing material

Even though EPDM is available in different mixing ratios (mainly due to the ethylene and diene content), the material has a number of fundamentally identical properties. Based on its saturated main chain, this synthetic rubber is characterized by very good aging resistance and high resistance to ozone, UV radiation, heat, and oxygen. In addition, seals and flat gaskets made of EPDM are heat and weather resistant. The material is also resistant to hot steam, hot water, and polar media, including diluted acids and alkalis, alcohols, ketones, salt solutions, and silicone oils. Finally, its high electrical resistance is also worth mentioning.

The various mechanical properties and high long-term stability of the elastomer make the material a versatile sealing material for a wide range of industrial applications. EPDM seals have high elasticity due to their typically high elongation at break, which is why they reliably adapt to the surfaces to be sealed even under dynamic or thermal stresses. Compared to other elastomers, flat seals made of EPDM have a pronounced resilience (compression set). This means that EPDM seals exhibit low permanent deformation after continuous compression. Another mechanical property of EPDM is its variable degree of hardness, which allows it to be used for almost any application.  The lower the Shore hardness (25-50 Shore A) of the material, the more flexible and adaptable the flat gasket produced. High degrees of hardness (80 Shore A) are particularly suitable for higher mechanical loads and resistant pressure stresses. The temperature range for EPDM seals varies depending on the material quality used. However, a rough range of approximately -40 °C to +120 °C can generally be specified. This material therefore offers excellent thermal properties for a wide variety of applications.

EPDM is usually sulphur cross-linked, but also exists as a peroxide cross-linked material. Peroxide cross-linking achieves a significantly higher temperature resistance. A higher ethylene content improves low-temperature flexibility and elasticity. A higher proportion of diene ensures a higher cross-linking speed and density as well as strength.

One disadvantage of this material is its instability when exposed to non-polar media such as fats, mineral oils, and fuels.

The limits and disadvantages of EPDM

When using EPDM seals, however, the limitations and disadvantages of the elastomer should also be taken into account. Flat or flange seals made of EPDM are not resistant to various chemical substances, such as fuels, lubricants, or solvents. Aggressive chemicals and cleaning agents in particular can damage EPDM seals and thus impair their function. NBR is a suitable sealing material for oil-resistant seals. In addition, temperature restrictions apply to EPDM seals. The temperature range of the material is approximately between -40°C and +140°C. However, the exact temperature range depends on the specific composition of the material. The exact temperature range is specified in the technical data sheet for the respective EPDM quality.

For higher temperature requirements, FKM or silicone should be considered in the elastomer range, as EPDM seals lose their elasticity at higher temperatures and the material becomes brittle. Another disadvantage of this material is its high gas permeability, which means that EPDM seals are not recommended for sealing gases such as oxygen or nitrogen. Finally, the material is not suitable for applications with high mechanical loads, as it has lower abrasion and tear resistance compared to other elastomers.

The sealing materials EPDM and NBR are synthetic rubbers, but they have some differences to each other. While EPDM is produced by polymerizing ethylene and propylene, NBR is produced from nitriles and butadiene. Accordingly, the two materials differ in terms of their resistances. Among other things, seals made of EPDM have good chemical resistance to polar media and organic and inorganic acids and bases. In addition, the gasket material is resistant to UV light and ozone and is therefore considered to be resistant to weathering and aging. The resistance to weathering and aging represents a major difference from NBR, as nitrile butadiene rubber does not have this resistance. However, NBR seals stand out primarily because of their good resistance to fuels, oils and solvents. Another difference between the two materials lies in the temperature range in which they can be used. Flat or flange gaskets made of EPDM can be used in a wider temperature range than gaskets made of NBR.

There are also significant differences compared to FKM rubber. Fluororubber gaskets have a higher temperature range than EPDM gaskets. The chemical resistance of Viton and FKM should also be emphasized as a distinguishing feature. While EPDM is not resistant to oils, greases and fuels and therefore has limitations when used in mechanical engineering, FKM has excellent resistance to the aforementioned media. However, when selecting a suitable sealing material, the better resistance to ageing and the lower price of EPDM compared to FKM should not be neglected.

In terms of temperature range and low-temperature flexibility, silicone flat gaskets have a thermal advantage over EPDM gaskets, as they can be used in a wider temperature range.

Production of EPDM as a sealing material

The synthetic rubber EPDM consists of the three main components ethylene, propylene and diene. The mixing ratio of the three components varies depending on the formulation and influences the properties of the EPDM. As a result, there are different EPDM variants, making it a versatile material for a wide range of industrial applications. For the production of EPDM/SBR, SBR (styrene-butadiene rubber) is added to the mixture.

The production of EPDM begins with the polymerization of the three main components, which are chemically combined in this step using a catalyst. In the next step, additional substances, such as fillers, are added to the resulting raw polymer. The final stage of the manufacturing process is vulcanization, in which "loose" polymer chains are turned into solid chemical bonds between the polymer chains. Sulphur or peroxides can be used as vulcanization agents. The choice of agent has an influence on the temperature resistance of the EPDM quality.

The way to your EPDM flat gasket

At Rehm Dichtungen Ehlers GmbH, you can obtain your customized flat or flange gaskets made of EPDM, as well as EPDM strips, directly from the gasket manufacturer. We manufacture almost all dimensions and contours and can flexibly adapt to your desired batch size.

The qualities presented and available at our company are first subjected to a quality control at goods receipt. Only then, after approval, is the sealing material stored in the form of rolls and sheets at the respective storage location. This enables us to guarantee a consistently high quality, also with regard to the respective sealing material.

EPDM belongs to the group of gasket materials that can be processed in all our manufacturing processes. The selection of the most suitable production process for your EPDM flat gaskets depends on the number of pieces, the respective contour and the thickness of the material. The unprocessed roll or sheet material is then processed into the individual EPDM flat gasket using the selected process.

It is also possible to apply a self-adhesive film to the roll or sheet material in advance and then process it into your self-adhesive EPDM gaskets using the manufacturing process. Self-adhesive gaskets serve exclusively as an assembly aid without changing the properties of EPDM. In addition to the production of flange and flat gaskets, we also offer unprocessed rolls or sheets as well as cut-to-size EPDM material by the meter for further processing. It is also possible for us to apply a self-adhesive finish to the material.

After completion of the production and a renewed quality control, the seals are packed and shipped to you.

Application areas of EPDM gaskets

EPDM is used as a sealing material in many areas and industries. The elastomer is available in rolls and sheets. As a gasket manufacturer, we primarily cut these into flat gaskets, strips and blanks as required.

For example, in the construction industry and in outdoor applications, seals made from this material are used as pipe seals for drinking water and wastewater systems, as EPDM is weather- and ozone-resistant.

EPDM is ideal as a sealing material for various water-carrying building elements, such as outdoor water pipes, seals in water taps, or door seals. Flat and flange seals are therefore also suitable for use in water treatment plants to prevent leaks and seepage. The black elastomer is also well suited as a substrate for green roofs, as it is root-resistant. In the automotive industry, EPDM seals and other components made from this material are increasingly being used in safety-related parts of automotive brakes. Another application we are aware of is the sealing of radiator, heating, and ventilation hoses. Due to their excellent aging resistance, EPDM seals are also used in various agricultural machines such as combine harvesters and crop strippers. In the field of mechanical and plant engineering, our EPDM seals are used for a wide variety of applications, as the versatility of the material meets the dynamic requirements. Due to their excellent resistance to hot and cold water in combination with KTW approval (E633), our products are a reliable component in the sanitary, heating, and drinking water industries.

Other technical rubber products include the area around the topic of conveyor belts, which is also covered in depth under the item conveyor belts. Finally, we also stock EPDM materials with approvals for contact with drinking water and foodstuffs.

As a sealing material, the material offers a diverse range of applications and performs excellently, providing reliable protection.

We will be happy to answer whether the elastomer is also suitable for your purposes. Please contact our customer service, who will be happy to provide you with comprehensive advice.