EPDM rubber is a rubber formed by solution copolymerization of ethylene and propylene, and then the third monomer (ENB) is introduced. EPDM is basically a saturated polymer with very good aging resistance, good weather resistance, excellent electrical insulation properties, good chemical resistance, and good impact elasticity. The main disadvantage of ethylene-propylene rubber is its slow vulcanization speed; it is difficult to use together with other unsaturated rubbers, and its self-adhesion and mutual adhesion are very poor, so the processing performance is not good.
According to the performance characteristics of ethylene-propylene rubber, it is mainly used in several fields that require aging resistance, water resistance, corrosion resistance, and electrical insulation, such as light-colored sidewalls for tires, heat-resistant conveyor belts, cables, wires, anti-corrosion linings, and gaskets , Building waterproof sheet, door and window sealing strip, household appliance accessories, plastic modification, etc.
Properties and uses of ethylene propylene rubber
Ethylene-propylene rubber is synthesized with ethylene and propylene as the main raw materials, and has outstanding aging resistance, electrical insulation properties and ozone resistance. Ethylene-propylene rubber can be filled with large amounts of oil and carbon black, and the product price is low. Ethylene-propylene rubber has good chemical stability, and its wear resistance, elasticity and oil resistance are close to those of styrene-butadiene rubber. Ethylene-propylene rubber has a wide range of uses. It can be used as tire sides, rubber strips, inner tubes, and automotive parts, as well as wire, cable sheathing, and high-voltage and ultra-high-voltage insulation materials. It can also manufacture light-colored products such as shoes and sanitary products.
Performance and improvement of ethylene propylene rubber
1. Low density and high filling ability
The density of ethylene propylene rubber is a relatively low type of rubber, with a density of 0.87. In addition, it can be filled with a large amount of oil and fillers, which can reduce the cost of rubber products and make up for the high price of ethylene propylene rubber, and for high Mooney value ethylene propylene rubber, the physical and mechanical energy after high filling is reduced. Not big.
2. 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 properties and fluidity at room temperature. Ethylene-propylene rubber products can be used for a long time at 120°C, and can be used briefly or intermittently at 150-200°C. Adding suitable antioxidants can increase its use temperature. EPDM rubber cross-linked with peroxide can be used under harsh conditions. EPDM rubber can reach more than 150 hours without cracking under the conditions of ozone concentration 50pphm and 30% stretching.
3. Corrosion resistance
Because ethylene propylene rubber lacks polarity and low degree of unsaturation, it has good resistance to various polar chemicals such as alcohols, acids, alkalis, oxidants, refrigerants, detergents, animal and vegetable oils, ketones and greases. ; But it has poor stability in fatty and aromatic solvents (such as gasoline, benzene, etc.) and mineral oil. The performance will also decrease under the long-term action of concentrated acid. In ISO/TO 762
In 0, nearly 400 kinds of corrosive gaseous and liquid chemicals have collected information on various rubber properties, and specified 1-4 levels to indicate their degree of action. 　　The effect of corrosive chemicals on rubber performance:
Grade Volume swelling rate/% Hardness reduction value Impact on performance
1 ＜10 ＜10 slight or none
2 10-20 ＜20 smaller
3 30-60 ＜30 Moderate
4 ＞60 ＞30 severe
4. Water vapor resistance performance
Ethylene-propylene rubber has excellent water vapor resistance and is estimated to be better than its heat resistance. In 230℃ superheated steam, there is no change in appearance after nearly 100h. However, under the same conditions, fluorine rubber, silicone rubber, fluorosilicone rubber, butyl rubber, nitrile rubber, and natural rubber experienced significant deterioration in appearance after a short period of time.
5. Superheated water resistance
Ethylene-propylene rubber also has better resistance to superheated water, but it is closely related to all vulcanization systems. Ethylene-propylene rubber with dimorpholine disulfide and TMTD as the vulcanization system, after being immersed in 125°C superheated water for 15 months, the mechanical properties change very little, and the volume expansion rate is only 0.3%.
6. Electrical performance
Ethylene-propylene rubber has excellent electrical insulation properties and corona resistance, and its electrical properties are better than or close to those of styrene-butadiene rubber, chlorosulfonated polyethylene, polyethylene and cross-linked polyethylene.
7. Elasticity
Because there are no polar substituents in the molecular structure of ethylene-propylene rubber, the cohesive energy of the molecule is low, and the molecular chain can maintain flexibility in a wide range, second only to natural negotiable and butadiene rubber, and can still be maintained at low temperatures.
8. Adhesion
Ethylene-propylene rubber lacks active groups due to its molecular structure and has low cohesive energy. In addition, the rubber is easy to bloom, and its self-adhesiveness and mutual adhesion are very poor.
2. Modified varieties of ethylene propylene rubber
Since the successful development of EPDM and EPDM rubbers in the late 1950s and early 1960s, a variety of modified ethylene propylene rubbers and thermoplastic ethylene propylene rubbers (such as EPDM/PE) have appeared in the world. The wide application of ethylene propylene rubber provides numerous varieties and grades. Modified ethylene propylene rubber mainly involves bromination, chlorination, sulfonation, maleic anhydride, maleic anhydride, silicone modification, nylon modification, etc. of ethylene propylene rubber. Ethylene propylene rubber also has grafted acrylonitrile, acrylic ester and so on. Over the years, many polymer materials with good comprehensive properties have been obtained by means of blending, copolymerization, filling, grafting, reinforcement and molecular compounding. Ethylene-propylene rubber has also been greatly improved in terms of performance through modification, thereby expanding the scope of application of ethylene-propylene rubber.