Introduction to EPDM
EPDM is a terpolymer of ethylene, propylene and non-conjugated dienes, which began commercial production in 1963. The annual consumption of the world is 800000 tons. The main characteristic of EPDM is its superior oxidation resistance, ozone resistance and corrosion resistance. As EPDM belongs to the polyolefin (PO) family, it has excellent vulcanization properties. Among all rubbers, EPDM has the lowest specific gravity and can absorb a large amount of fillers and oil without affecting the properties. Therefore, it can produce low-cost rubber compounds.
Performance
- Low density and high filling
Ethylene-propylene rubber has a lower density of 0.87. In addition, a large amount of oil can be filled and filling agent can be added, which can reduce the cost of rubber products, make up for the shortcomings of the high price of EPDM raw rubber, and for EPDM with high Mooney value, the physical and mechanical energy after high filling is not reduced significantly.
- Aging resistance
Ethylene-propylene rubber has excellent weather resistance, ozone resistance, heat resistance, acid and alkali resistance, water vapor resistance, color stability, electrical properties, oil filling and normal temperature fluidity. Ethylene-propylene rubber products can be used for a long time at 120 ℃, and can be used temporarily or intermittently at 150 – 200 ℃. The use temperature can be increased by adding appropriate antioxidant. EPDM crosslinked with peroxide can be used under harsh conditions.Under the condition of ozone concentration of 50 pphm and stretch of 30%, EPDM can not crack for more than 150 h.
- Corrosion resistance
Due to the lack of polarity and low unsaturation of ethylene-propylene rubber, it has good resistance to various polar chemicals such as alcohol, acid, alkali, oxidant, refrigerant, detergent, animal and vegetable oil, ketone and grease; However, it has poor stability in aliphatic and aromatic solvents (such as gasoline, benzene, etc.) and mineral oils. Under the long-term action of concentrated acid, the performance will also decline.
- Water vapor resistance
EPDM has excellent water vapor resistance and is estimated to be superior to its heat resistance. In 230 ℃ superheated steam, there is no change in appearance after nearly 100 h. However, under the same conditions, fluorine rubber, silicon rubber, fluorosilicone rubber, butyl rubber, nitrile rubber and natural rubber experienced obvious deterioration in appearance in a relatively short time.
- Hot water resistance
Ethylene-propylene rubber also has good resistance to superheated water, but it is closely related to all curing systems. The mechanical properties of ethylene-propylene rubber with morpholine disulfide and TMTD as curing system changed little after soaking in 125 ℃ superheated water for 15 months, and the volume expansion rate was only 0.3%.
- Electrical performance
Ethylene-propylene rubber has excellent electrical insulation and corona resistance, and its electrical properties are superior to or close to those of styrene-butadiene rubber, chlorosulfonated polyethylene, polyethylene and cross-linked polyethylene.
- Elasticity
Because there is no polar substituent in the molecular structure of ethylene-propylene rubber and the molecular cohesion energy is low, the molecular chain can maintain flexibility in a wide range, second only to natural rubber and cis-polybutadiene rubber, and can still maintain at low temperature.
- Adhesion
Due to the lack of active groups in the molecular structure of ethylene-propylene rubber, low cohesion energy, and easy frost spraying of rubber compound, the self-adhesion and mutual adhesion are very poor.
Advantage
- It has a high performance-price ratio. The density of raw rubber is only 0.86~0.90g/cm3, which is the most common rubber with the lightest density of raw rubber; It can also be filled in large quantities to reduce the cost of rubber compound.
- Excellent aging resistance, weather resistance, ozone resistance, sunlight resistance, heat resistance, water resistance, water vapor resistance, UV resistance, radiation resistance and other aging properties. When used with other unsaturated diene rubber such as NR, SBR, BR, NBR, and CR, EPDM can play the role of polymer antioxidant or antioxidant.
- Excellent chemical resistance, acid, alkali, detergent, animal and vegetable oil, alcohol, ketone, etc; Excellent resistance to water, superheated water and steam; Resistance to polar oil.
- Excellent insulation performance, volume resistivity 1016Q · cm, breakdown voltage 30-40MV/m, dielectric constant (1kHz, 20 ℃) 2.27.
- It is applicable to a wide range of temperatures, with a minimum operating temperature of – 40~- 60 ℃, and can be used at 130 ℃ for a long time.
Post time: Jan-10-2023
