EPDM rubber

Ethylene-propylene -diene rubber (abbreviation EPDM, ethylene -propylene-diene ) is a terpolymer elastomer ( rubber ), and thus a synthetic rubber. EPM ( ethylene propylene rubber ) and EPDM belong to the random copolymers with saturated polymer backbone ( according to DIN designation: M group, in contrast, consist of rubbers with unsaturated hydrocarbon chain for the R group, such as natural rubber NR, styrene -butadiene rubber SBR).

The preparation is carried out with the metallocene or Ziegler-Natta catalysts based on vanadium compounds and aluminum alkyl chlorides. As diene, unconjugated dienes are used, of which only one double bond on the polymer chain formation is involved, so that more double bonds remain outside the direct chain backbone, and in contrast to the EPM may be vulcanized with sulfur, during the EPM may be only the peroxide cross-linked. As the diene component, ethylidenenorbornene (ENB IUPAC: 5-ethylidene -2-norbornene ), dicyclopentadiene (DCP ), 1,4- hexadiene, or used. The dienes differ with respect to the rate of crosslinking. DCP has the lowest, ENB the highest reactivity. Regarding the costs, the order is reversed.

Properties and Uses

The saturated scaffold leads to properties such as high weather resistance and moisture resistance, and ozone resistance as well as high thermal resistance. It is used because of its high elasticity and good chemical resistance, among others, for various seals, such as O -rings for mechanical seals or gaskets. EPDM is a common material used for tubes, which are used for steam or hot water.

For particularly high-quality EPDM flat roof and waterproofing membranes are still being manufactured. Special variants here are coated with bitumen or fleece EPDM waterproofing membranes. Absorber mats for heating swimming pools are made of EPDM. These are UV and weather resistant, walkable and they were full of frost. Absorber mats made of EPDM are resistant to chlorinated water. Even high-quality pond liner is made from EPDM. It is particularly suitable, as it is also highly flexible when cold, UV resistant and durable for this purpose.

Commercial EPDM rubber types

Commercial EPDM rubbers have an ethylene content of 45-75 % by weight. Polymers with low ethylene content ( 45-55 wt % ) are amorphous and have the best low-temperature flexibility. With increasing content of ethylene increases the crystallinity (pure linear polyethylene is highly crystalline ). EPDM medium ethylene content ( 55-65 % by weight ) is partially crystalline. Terpolymers about 65 % by weight of ethylene have larger crystalline regions and therefore behave as thermoplastic elastomers; these have a high tensile strength already in the uncrosslinked state.

The diene content of commercial products is from 2-12 % by weight, corresponding to a proportion of 3-16 double bonds per 1000 carbon atoms. A higher diene content results in a higher curing rate, higher strength and lower compression set. The aging, weathering and ozone resistance decreases, however, with increasing diene content.

EPDM rubber

Properties and Uses

Commercial EPDM rubber types

Further Reading