EPDM rubber (ethylene propylene diene methylene rubber)




Due to its all-rounder properties, the material ethylene propylene diene monomer (EPDM) has found extensive application in a wide range of industrial areas. After its introduction in the 1960s, the use of EPDM increased rapidly, and it is now one of the most common elastomers.  Its versatility and good resistance against weather have made EPDM the material of choice for technical rubber products.   

In this blog post, we will discuss the various properties of EPDM in detail.

First of all, it should be emphasized that that properties vary not only according to the specific blend of a compound; they are also directly affected by the type of crosslinking (peroxide crosslinking or sulfur crosslinking). This is dealt with later in the blog.  

Mechanical properties of EPDM

A very characteristic property of EPDM is its excellent durability. For many EPDM blends, the addition of anti-aging agents is unnecessary.

Regarding its other mechanical properties, EPDM can be thought of as a general-purpose synthetic rubber.

The tear strength and elongation at break of EPDM mixes, and their tear propagation resistance, are average to good. The same applies to elongation at break.

With regard to compression set, EPDM has very good values for blends cured with peroxide, whereas sulfur-crosslinked compounds are only average in this category. The degree of vulcanization is also an important parameter.

Thermal properties of EPDM

There are big variations between the thermal properties of the differently crosslinked EPDM compounds.

Peroxide-crosslinked EPDM materials have better temperature resistance than sulfur-crosslinked compounds. Peroxide-crosslinked EPDM blends are heat resistant, under continuous heat, to about 130° C, although this can increase to 170° C for short periods. The compression set of peroxide crosslinked EPDM blends is very good, even at high temperatures.

In general, the heat resistance of peroxide-crosslinked EPDM is roughly comparable to that of HNBR (hydrogenated acrylonitrile-butadiene rubber).    

Conversely, in the case of sulfur-crosslinked compounds, it is recommended that the temperature does not exceed 100° C for continuous exposure.

The cold flexibility of EPDM is reasonable and highly dependent on the ethylene content of the base mix. Cold flexibility is better for a lower ethylene content (40 to 50 percentage by mass of components). However, a low ethylene content generally leads to inferior dynamic properties of EPDM. On the other hand, a high ethylene content (60 to 70 percentage by mass of components) results in poorer cold behavior of the material. Interestingly, this does not apply to the compression set, which increases with increased ethylene content, even in cold weather.  

(Chemical) resistance of EPDM

EPDM is popular in many industries because of its outstanding resistance against weather and ozone. This, in combination with its very good resistance to polar chemicals, such as water, wastewater, alkalis, alcohol and glycols, has opened up multiple potential applications. In addition, acids and various organic and inorganic bases are not a problem for EPDM. 

It also shows very good resistance to hot water and water vapor up to 130° C. With a suitable blend formulation, this may even be increased to 150° C.

Furthermore, EPDM has very good insulation properties due to its very high level of electrical resistance.

However, the material EPDM shows weaknesses in contact with mineral oils, fuels and fats and here EPDM is almost unusable. There are also problems with aliphatic, chlorinated and aromatic hydrocarbons.

Another disadvantage of EPDM is that it is extremely difficult to achieve flame retardancy for mixes.

EPDM applications

EPDM is used in many industrial areas due to its wide range of properties

The automotive industry is a big buyer of EPDM products. Typical EPDM products include coolant hoses, heating hoses, ventilation hoses and brake hoses. Profile seals for doors, windows or the trunk of vehicles are also made from EPDM. The same applies to cable bushings and brake seals. And a product which you, as motorists, often come into contact is made of EPDM: windscreen wiper blades.  

In the construction sector, EPDM is used for window seals, cladding seals or pipe seals. Roof foils and floor coverings for play or sports surfaces also number among its applications.

Molded parts that are made from certified and tested EPDM are common in the drinking water and wastewater sector, where they are mostly used as gaskets.

In the electrical industry, EPDM is found in cable sheathings, couplings, wire insulation and flange gaskets.

The properties of EPDM can also be beneficial in dynamic applications. EPDM membranes made to withstand enormous stresses, while being crucial for functionality, are manufactured for the pneumatics and pump sector. Profile seals and O-rings are also often made of EPDM because of its good compression set and excellent durability.

Overview of EPDM properties

In conclusion, here is a recap of the properties of EPDM (ethylene-propylene-diene rubber).

Remember, this is only a general guide and not to be used for your ultimate selection of materials. The individual properties of blends can be positively and negatively influenced by targeted formulation and as such may be different from the information presented here.

The rating ranges from ☆☆☆☆☆ (very poor) to ★★★★★ (very good).

 Mechanical characteristics:  
 Hardness range: Shore A 25 to 95
 Tensile strength: ★★★☆☆
 Elongation at break: ★★★☆☆
 Tear strength: ★★★☆☆
 Compression set at high temperatures:  ★★★★☆
 Compression set at low temperatures: ★★★★☆
 Rebound resilience: ★★★★☆
 Abrasion resistance: ★★★☆☆
 Thermal properties:  
 Low-temperature flexibility: ★★★☆☆
 Thermal resistance: ★★★☆☆
 (Chemical) resistance:  
 Gasoline: ☆☆☆☆☆
 Mineral oil (100° C): ★☆☆☆☆
 Acids: ★★★★★
 Alkalis: ★★★★★
 Water (100° C): ★★★★★
 Harsh weathering and ozone: ★★★★★
 UV/light: ★★★★☆

For more details about properties or chemical resistance, or if you have a query about a particular application, please do not hesitate to contact us.  

If you have a question about this blog post or would like us to discuss a particular aspect of elastomers in an upcoming blog, please email us on info@hepako.de   

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