EPDM rubber

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EPDM rubber (ethylene propylene diene monomer rubber) is an elastomer which is characterized by wide range of applications.The E refers to Ethylene, P to Propylene, D to diene and M refers to polymethylene-the repeating unit. The diene(s) currently used in the manufacture of EPDM rubbers are DCPD (dicyclopentadiene), ENB (ethylidene norbornene) and VNB (vinyl norbornene).

The ethylene content is around 45% to 75%. More amount of Ethylene leads to better extrusion behaviour and more propylene leads to easier mixing and moulding. The diene content will be normally around 4% to 5%. However if EPDM has to be blended with faster curing rubbers, the diene content may go up to 10%.

EPDM rubber is used in vibrators and seals; glass-run channel; radiator, garden and appliance hose; tubing; washers; belts; and electrical insulation. It is also used as a medium for water resistance in high-voltage polymeric cable jointing installations, roofing membrane, geomembranes, rubber mechanical goods, plastic impact modification, thermoplastic, vulcanizates, as a motor oil additive, pond liner, electrical cable-jointing, RV roofs, and chainmail applications.

EPDM exhibits satisfactory compatibility with fireproof hydraulic fluids, ketones, hot and cold water, and alkalis, and unsatisfactory compatibility with most oils, gasoline, kerosene, aromatic and aliphatic hydrocarbons, halogenated solvents, and concentrated acids.

The main properties of EPDM are its outstanding heat, ozone and weather resistance. The resistance to polar substances and steam are also good. It has excellent electrical properties. It has the ability to retain light colour.

Typical properties of EPDM vulcanisates are given below. EPDM can be compounded to meet specific properties to a limit depending first on the EPDM polymers available, then the processing and curing method(s) employed. EPDMs are available in a range of molecular weights (indicated in terms of Mooney viscosity ML(1+4)@125°C), varying levels of ethylene, third monomer and oil content.

Mechanical Properties
Hardness, Shore A	40 - 90
Tensile Strength, Ultimate	25 MPa
Density	Can be compounded from 0.90 to >2.00 gcm-³
Abrasion resistance	450 mm3

Thermal Properties
CTE, linear 68°F	576 µm/m-°C
Maximum Service Temperature, Air	100-120 °C
Minimum Service Temperature, Air	-54 °C
Glass Temperature	-54 °C

[edit] Common Application

EPDM rubber is commonly used in weatherseals on all vehicles. This includes door seals, window seals, trunk seals, and sometimes hood seals. Frequently these seals are the source of noise due to movement of the door versus the car body. This is due to friction between the EPDM rubber and the mating surface (car painted sheet metal or glass). This can be alleviated using specialty coatings that are applied at the time of manufacture of the weatherseal, not as an aftermarket application. Such coatings can also greatly increase the chemical resistance of EPDM rubber. Some vehicle manufacturers such as General Motors also recommend a light application of silicone dielectric grease to weatherstripping to reduce noise. EPDM is also commonly used as a material for the face seals of industrial respirators, most frequently chosen where the use of silicone must be avoided, typically in automotive paint spray environments.