EPDM rubber (ethylene propylene diene monomer rubber), a type of synthetic rubber, is an elastomer characterized by a wide range of applications. This is an M-Class rubber where the ‘M’ in M-Class refers to its classification in ASTM standard D-1418; the M class includes rubbers having a saturated chain of the polyethylene type. Dienes used in the manufacture of EPDM rubbers are dicyclopentadiene (DCPD), ethylidene norbornene (ENB), and vinyl norbornene (VNB). EPDM rubber is closely related to ethylene propylene rubber: ethylene propylene rubber is a copolymer of ethylene and propylene, whereas EPDM rubber is a terpolymer of ethylene, propylene, and a diene-component.
The ethylene content is around 45% to 85%. The higher the ethylene content, the higher the loading possibilities of the polymer, better mixing, and extrusion. Peroxide curing these polymers gives a higher crosslink density compared with their amorphous counterpart. The amorphous polymer is also excellent in processing. Processability is very much influenced by their molecular structure. The dienes, typically comprising from 2.5% to 12% by weight of the composition, serve as sites of cross-links when curing with sulphur and resin; with peroxide cures, the diene (or third monomer) functions as a coagent, which provides resistance to unwanted tackiness, creep, or flow during end use.
PROPERTIES OF EPDM RUBBER
For the first time, the semi-industrial production of copolymers of ethylene with propylene was started in 1959 in Italy. Currently, various types of ethylene-propylene rubbers are produced in a number of countries.
The saturated nature of the copolymer determines the properties of rubber, which are characterized by high resistance to all types of aging and ozone resistance. According to these indices, EPDM rubber significantly exceeds rubbers based on natural and synthetic elastomers of general purpose. Below are the aging factors for 96 hours at different temperatures of rubbers based on NR and EPDM on the of tensile strength and relative elongation:
Properties of EPDM rubber do not change after aging for 15 days at 25 ° C in 90% sulfuric acid and in 30% nitric acid. However, rubbers based on ethylene-propylene have unsatisfactory oil and gasoline resistance. EPDM is well combined with soot, oil and poly-olefins, but it is incompatible with most highly unsaturated rubbers, especially non-polar ones.
EPDM rubber is a very elastic material that has a high resistance to UV radiation. The material also has good resistance to ozone, low and high temperatures, and has a high resistance to oxidation.
EPDM rubber has a black color, is resistant to aging, so it is often used in the automotive and construction industries. The distinctive properties of EPDM rubber make it possible to create rings from this material used in such household appliances as washing machines and dishwashers.
Seals made from EPDM rubber are resistant to dilute acids with alkalis, ketones, esters and some types of alcohol. This allows the use of EPDM seals for the manufacture of a wide variety of products, including those that will be exposed to corrosive media.
If we compare EPDM rubber with other materials, then we can say that it is one of the most resistant – only slightly exceeds the fluorine rubber for workability in corrosive environments.
One of the few disadvantages of EPDM rubber is that it has almost no oil resistance. In addition, this material poorly forms double bonds, because of what it is extremely difficult to attach to the metal.
- Hot water and hot steam up to +180 °С
- Heavily flammable pneumatic fluids of the HFD-R group without mineral oil additives
- Detergents, sodium (soda) and potassium alkali
- A large number of organic and inorganic bases and acids
- Saline solutions and oxidation-active media
- Heavily flammable pneumatic fluids of the HFC group (glycol water, if no mineral oils are guaranteed)
- A large number of solvents (eg alcohol = alcohols, ketones, ester)
- Glycol-based brake fluids
- Silicone oils and fats (oils can lead to reduction, testing is recommended)
Low / zero resistance
- Aliphatic hydrocarbons (propane, butane, gasoline)
- Mineral oils and fats
- Aromatic and chlorinated hydrocarbons
- Vegetable and animal oils and fats
- Biodegradable hydraulic fluids
- Heavily flammable pneumatic liquids of the HFA group, HFB and HFD-S
APPLICATION OF EPDM RUBBER
Ethylene-propylene rubbers have good dielectric properties, which in combination with high weather resistance and increased heat resistance makes them very promising materials for cable and electrical industry. They are used for the production of conveyor belts, protective clothing, linings for chemical equipment, hoses and gaskets for working with corrosive liquids, drive belts, car parts, etc.
A common use is in vehicles: door seals, window seals, trunk seals, and sometimes hood seals. Frequently, these seals are the source of noise due to movement of the door against the car body and the resulting friction between the EPDM rubber and the mating surface (painted sheet metal or glass). This noise can be alleviated using specialty coatings that are applied at the time of manufacture of the weather seal. Such coatings can also improve the chemical resistance of EPDM rubber. Some vehicle manufacturers also recommend a light application of silicone dielectric grease to weatherstripping to reduce noise. Other uses in vehicles include cooling system circuit hoses where water pumps, thermostats, EGR valves, EGR coolers, heaters, oil coolers, radiators, and degas bottles are connected with EPDM hoses, as well as charge air tubing on turbocharged engines to connect the cold side of the charge air cooler (intercooler) to the intake manifold.
EPDM rubber is used in seals (for example, it is used in cold-room doors since it is an insulator, as well as in the face seals of industrial respirators in automotive paint spray environments. EPDM is also used in glass-run channels, radiators, garden, and appliance hose, tubing, pond liners, washers, belts, electrical insulation, vibrators, O-rings, solar panel heat collectors, and speaker cone surrounds.
It is also used as a medium for water resistance in electrical cable-jointing, roofing membranes (since it does not pollute the run-off rainwater, which is of vital importance for rainwater harvesting), geomembranes, rubber mechanical goods, plastic impact modification, thermoplastic, vulcanizates, and many other applications. Colored EPDM granules are mixed with polyurethane binders and troweled or sprayed onto concrete, asphalt, screenings, interlocking brick, wood, etc. to create a non-slip, soft, porous safety surface for wet-deck areas such as pool decks and as safety surfacing under playground play equipment (designed to help lessen fall injury).
BASIC PHYSICAL AND MECHANICAL CHARACTERISTICS OF EPDM
|Properties||Unit of measure||Value|
|Residual deformation 100oС/22hrs||%||≤10|
|Strength at a wide rupture||N/mm||10|
|Elasticity of rebound||%||38|
|Minimum application temperature||oС||-50|
|Maximum application temperature||oС||+150|