As with all plastics, EPDM is a polymer composed of various chemical building blocks known as monomers. These monomers are in detail:

• Ethene, or ethylene, is a gaseous raw material from the petroleum industry.
• Propene, or propylene, is also a hydrocarbon-based gas.
• Diene is an unsaturated hydrocarbon with double bonds between the carbon atoms.

These three monomers form the finished plastic EPDM in a so-called polymerization reaction. Its precise properties can be very well influenced by the mixing ratio of the three components and the selection of the diene. In this way, EPDM can be optimally adapted to the intended use and its properties optimized.

Ethylene-propylene-diene rubber, despite its good adaptability, has some properties and features that are characteristic of this synthetic rubber and make it versatile. These include:

• flexible adaptability to different applications - through the selection of suitable monomers
• high mechanical elasticity - typical of a synthetic rubber
• resistance to a wide range of chemicals - due to the special chemical structure
• high thermal resistance - crucial for a wide range of applications
• good weathering and ozone resistance - ensures long-term outdoor use
  
  

Flexible physical properties, depending on the intended use

Like most plastics, EPDM is synthesized by polymerization. In this process, the three monomers can be mixed in different proportions, which means that the resulting products differ in their chemical, physical and mechanical properties.

Even more far-reaching adjustments to the properties of EPDM can be achieved through the targeted selection of the third monomer. EPDM is generally a synthetic rubber with a relatively high density. The average density is 1.4 g/cm³, but this can be varied considerably by selecting the monomers..

High mechanical elasticity

Mechanical elasticity is the property of a material to deform under the influence of mechanical energy and then return to its original shape. This change in shape is therefore not permanent as in the case of thermal deformation.

Due to its high mechanical elasticity, EPDM is used, among other things, as a

• Spring element in industrial plants,
• sealing lip in car doors and
• fall protection mats in children's playgrounds.

Even though EPDM can be varied very well in its properties, the following values can be considered as a guideline for the elastic properties of EPDM:

• Shore hardness A: 25 ° to 80 °.
• Rebound elasticity: up to 45
• Elongation at break: up to 550
• Tensile strength: 3.5 MPa to 12 MPa
  
  

EPDM is resistant to most chemicals

Ethylene-propylene-diene rubbers have a saturated main chain without double bonds between the carbon atoms. This makes EPDM a largely non-polar molecule with excellent resistance to polar solvents, such as alcohols, ketones, esters, acids and alkalis. EPDM is also highly resistant to water and water vapor.

Greases and mineral oils, on the other hand, attack ethylene-propylene-diene rubbers and can even dissolve them completely after prolonged exposure.

The thermal resistance of EPDM allows a wide range of application temperatures

The saturated main chain of the EPDM molecule also ensures high temperature resistance. Thus, the application range of the elastomer extends from -60 °C to +160 °C. Below this temperature, EPDM begins to become brittle and loses its elastic properties. Above 160 °C, the plastic begins to undergo permanent thermal deformation as it reaches its melting point.

UV and ozone resistance make EPDM ideal for outdoor use

EPDM is characterized by long-term aging resistance. UV rays and ozone do not cause any noticeable changes to materials made of ethylene-propylene-diene rubber. Roofing membranes, high-quality pond liners and swimming pool tread mats are made of EPDM. The elastomer is also increasingly being used as cover sheets.

Like all plastics, ethylene-propylene-diene rubber is produced by a polymerization reaction. Two different processes have become established for this purpose in recent years:

Synthesis using classic Ziegler-Natta catalysts - In this process, the reaction is enabled by mixed organometallic catalysts. The catalysts used here include magnesium chloride, triethylaluminum and titanium tetrachloride.

The second reaction route involves synthesis with Kaminsky catalysts. These catalysts have only recently become established. The process is based on the use of metallocenes, i.e. organometallic compounds.

In both synthesis processes, subsequent vulcanization with peroxides or sulfur is possible.

After synthesis, ethylene-propylene-diene rubber can be shaped into a wide variety of forms to serve a variety of purposes. Most commonly, EPDM is formed into rolls after synthesis, which can be further processed using various techniques:

• In hot air welding, EPDM sheets are first heated and then overlapped and fused together.
• Seam tape vulcanization is used to attach ethylene-propylene-diene rubber to metal components.
• Adhesives and adhesive tape bond EPDM films to themselves or to underlying materials.

During further processing, it must always be taken into account that ethylene-propylene-diene rubber is difficult to bond to materials such as wood, metal and concrete due to its molecular structure. However, with suitable auxiliaries, this disadvantage can be compensated for in most cases.

EPDM is one of the most versatile elastomers currently available. The reasons for this include its

• insensitivity to weathering,
• excellent UV and ozone resistance, and resistance to temperature fluctuations.
• resistance to temperature fluctuations.

Therefore, the material finds a wide range of applications in home and garden construction. In addition, EPDM is valued as rubber in the automotive industry and in molded part construction. Material made of EPDM is also frequently used in the skilled trades.

EPDM is often used for sealing and insulation

Due to its resistance to water, water vapor and polar solvents, films made of ethylene-propylene-diene rubber are often used as sealing materials:

• Its extremely good weather resistance makes EPDM foil the ideal material for sealing roofs over large areas. In this case, the roofing membranes are laid overlapping and thermally welded.
• When used as a pond liner, EPDM sheets are usually not thermally bonded but joined together using special adhesives. The good formability of EPDM sheets allows artistic and creative shapes.

Furthermore, ethylene propylene diene rubber is suitable for insulation and sealing. Insulation sheets made of EPDM are suitable for vibration insulation or serve as fall protection under climbing frames.

Water pipes made of EPDM convince with good pressure resistance and long service life.

Door seals for indoor and outdoor use offer good elasticity combined with high dimensional stability and weather resistance.

Components made of ethylene-propylene-diene rubber can be used wherever they do not come into contact with mineral oils or fuels and lubricants.

From city cars to off-roaders: EPDM is also widely used in the automotive industry

Cars are constantly exposed to dirt, water, wind and weather. At the same time, with doors, flaps and hoods, they have many moving parts that must be reliably sealed. As a joint and door seal, EPDM is used in a wide variety of applications in the automotive industry. Its excellent aging resistance and suitability for use over a wide temperature range ensure high reliability and robustness of the seals used.

In the manufacture of sports equipment, the advantages of EPDM become apparent

EPDM belongs to the elastomers with relatively high density. This means that materials made of ethylene propylene diene rubber are comparatively heavy for a given size. Therefore, EPDM granules are suitable, for example, as filling material for punching bags and other training equipment for martial arts.

Ethylene-propylene-diene rubber is not the only high-quality elastomer available on the market. Each of these polymers has very specific properties that allow a targeted selection of the appropriate material. The main alternatives for ethylene-propylene-diene rubber include:

• NBR - butadiene-acrylonitrile rubber (English: Nitrile Butadiene Rubber).
• Fluoroelastomers - known under the trade name Viton
• SBR - Styrene Butadiene Rubber (English: Styrene Butadiene Rubber)
  
  

EPDM is more suitable for outdoor use than NBR

Ethylene-propylene-diene rubber is very well suited for outdoor use. This is due to its UV and ozone resistance, which is significantly higher than that of NBR. Ethylene-propylene-diene rubber is also characterized by very high resistance to water, water vapor, acids, alkalis and other polar solvents.

In contrast, NBR is always used when the plastic comes into contact with mineral oils and fuels, against which there is very high resistance. However, the weathering and ozone resistance of NBR is comparatively low, although its resistance to cold can be increased by certain additives.

Viton is of limited use in some areas

Fluoroelastomers are available on the market under the trade name Viton from DuPont Performance Elastomers. They are sold under other names by other manufacturers. In contrast to components made of ethylene-propylene-diene rubber, Viton components are not resistant to water, water vapor, acids and alkalis. This makes Viton unsuitable for outdoor use and wherever it comes into contact with polar solvents, although its weather resistance is comparable to that of EPDM. However, Viton is highly resistant to mineral oils and fuels and lubricants.

Compared to SBR, EPDM convinces by its high weather resistance

SBR is an inexpensive and widely used alternative to ethylene-propylene-diene rubber for indoor applications. With similar properties, the weathering and ozone resistance of SBR falls far short of that of ethylene-propylene-diene rubber. In addition, styrene-butadiene rubber has very low flame resistance. Therefore, it can serve as a low-cost alternative when the full performance potential of ethylene-propylene-diene rubber does not need to be exploited.