Ethylene propylene diene monomer (EPDM) is a rubber made of ethylene and propylene through solution copolymerization, and then introduced into the third monomer (ENB). EPDM is basically a saturated polymer with excellent aging resistance, weather resistance, electrical insulation, chemical corrosion resistance and impact elasticity. The main disadvantage of ethylene propylene rubber is its slow curing speed; It is difficult to blend with other unsaturated rubbers, and the self adhesion and mutual adhesion are very poor, so the processing performance is poor.
According to the performance characteristics of ethylene propylene rubber, it is mainly used in the fields that require aging resistance, water resistance, corrosion resistance and electrical insulation, such as light color sidewalls of tires, heat-resistant transport belts, cables, wires, anti-corrosion linings, sealing washers, building waterproof sheets, door and window sealing strips, household electrical appliances 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, with outstanding aging resistance, electrical insulation and ozone resistance. Ethylene propylene rubber can be filled with a large amount of oil and carbon black. The product price is low. Ethylene propylene rubber has good chemical stability, and its wear resistance, elasticity, and oil resistance are similar to those of styrene butadiene rubber. Ethylene propylene rubber is widely used as tire side, rubber strip, inner tube and auto parts, as well as wire, cable sheath 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、 1. Low density and high filling
Ethylene propylene rubber is a kind of rubber with a lower density of 0.87. In addition, a large amount of oil can be filled and fillers can be added, which can reduce the cost of rubber products and make up for the high price of raw rubber of ethylene propylene rubber. In addition, for ethylene propylene rubber with high Mooney value, the physical and mechanical energy after high filling will not be reduced by much.
2. Aging resistance
Ethylene propylene rubber has excellent weather resistance, ozone resistance, heat resistance, acid and alkali resistance, water vapor resistance, color stability, electrical performance, oil filling and room temperature fluidity. Ethylene propylene rubber products can be used for a long time at 120 ℃, and can be used briefly 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. When the ozone concentration of EPDM is 50 pphm and the stretching time is 30%, the EPDM can reach 150 h without cracking.
3. 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 fatty and aromatic solvents (such as gasoline, benzene, etc.) and mineral oils. The performance will also decline under the long-term action of concentrated acid. In ISO/TO 7620, the data on the effects of nearly 400 corrosive gaseous and liquid chemicals on the properties of various rubbers are collected, and the 1-4 grades are specified to indicate their effects. The effects of corrosive chemicals on the properties of rubbers are as follows:
4. Water vapor resistance
EPDM has excellent steam resistance and is estimated to be superior to its heat resistance. In the 230 ℃ superheated steam, the appearance does not change after nearly 100 hours. However, under the same conditions, the appearance of fluorine rubber, silicon rubber, fluorosilicone rubber, butyl rubber, nitrile rubber and natural rubber deteriorated significantly in a short time.
5. Resistance to superheated water
Ethylene propylene rubber also has good resistance to superheated water, but it is closely related to all vulcanization systems. The mechanical properties of ethylene propylene rubber (EPR) vulcanized with dimorphine disulfide and TMTD were little changed after being immersed in 125 ℃ superheated water for 15 months, and the volume expansion rate was only 0.3%.
6. 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.
7. Elasticity
Because ethylene propylene rubber has no polar substituents in its molecular structure and low molecular cohesion energy, its molecular chain can maintain flexibility in a wide range, second only to natural rubber and cis polybutadiene rubber, and can still maintain at low temperatures.
8. Adhesion
Due to the lack of active groups in the molecular structure of ethylene propylene rubber, the cohesion energy is low, and the rubber is easy to spray, so the self adhesion and mutual adhesion are very poor.
2、 Modified varieties of ethylene propylene rubber
Since the development of EPDM and EPDM rubber in the late 1950s and early 1960s, there have been many kinds of modified EPDM rubber and thermoplastic EPDM rubber (such as EPDM/PE) in the world, thus providing many varieties and grades for the wide application of EPDM rubber. The modification of ethylene propylene rubber mainly involves bromination, chlorination, sulfonation, maleic anhydride, maleic anhydride, silicone modification, nylon modification, etc. Ethylene propylene rubber is also grafted with acrylonitrile, acrylate, etc. Over the years, many polymer materials with good comprehensive properties have been obtained by means of blending, copolymerization, filling, grafting, reinforcement and molecular compounding. The properties of ethylene propylene rubber have also been greatly improved through modification, thus expanding the application scope of ethylene propylene rubber.
Brominated ethylene propylene rubber is processed by brominating agent in the open mill. Brominated ethylene propylene rubber can improve its vulcanization speed and adhesion performance, but its mechanical strength decreases. Therefore, brominated ethylene propylene rubber is only suitable for the intermediate layer for bonding ethylene propylene rubber with other rubbers.
Chlorinated ethylene propylene rubber is made by passing chlorine into ethylene propylene diene monomer solution. The chlorination of ethylene propylene rubber can improve the vulcanization speed, the compatibility with unsaturated rubber, the flame resistance, oil resistance, and the adhesion performance.
Sulfonated ethylene propylene rubber is made by dissolving ethylene propylene diene monomer in solvent and treating it with sulfonated agent and neutralizer. Sulfonated ethylene propylene rubber (SEPR) will be widely used in adhesives, coated fabrics, building waterproof lean meat, anti-corrosion lining, etc. due to its good physical properties and adhesion properties of thermoplastic elastomer.
Acrylonitrile grafted ethylene propylene rubber (EPR) was grafted with acrylonitrile at 80 ℃ using toluene as solvent and benzyl peroxide as initiator. Acrylonitrile modified ethylene propylene rubber not only retains the corrosion resistance of ethylene propylene rubber, but also obtains the oil resistance equivalent to butyronitrile-26, with good physical and mechanical properties and processing properties.
Thermoplastic ethylene propylene rubber (EPDM/PP) is a blend of ethylene propylene diene monomer (EPDM/PP) and polypropylene. At the same time, ethylene propylene rubber reaches the expected cross-linking degree. It not only retains the inherent characteristics of ethylene propylene rubber in performance, but also has significant processing properties of injection, extrusion, blow molding and calendering of thermoplastic.
In addition, modified ethylene propylene rubber includes chlorosulfonated ethylene propylene rubber discussion, acrylate graftedethylene propylene rubber, etc.