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Ethylene-Propylene-Diene Monomer

Ethylene-Propylene-Diene Monomer

EPDM is ethylene, propylene and non conjugated diene terpolymer, 1963 began commercial production. Consumption around the world each year is the main characteristic of 80 million tons of.EPDM is the superior oxidation resistance, ozone resistant and anti erosion ability. Due to the polyene (PA66) hydrocarbon family belonging to the EPDM rubber. It has excellent curing characteristics. In all the rubber, EPDM has the lowest proportion. It can absorb a large amount of filler and oil and do not affect the properties. So it can be made low cost of rubber compounds.
Folding molecular structure and properties
EPDM is ethylene, propylene and non conjugated diene terpolymer. Dienes with special structure, one of only two keys can be copolymerized, unsaturated double bond is mainly the chain. Another unsaturated won´t become the polymer backbone, will become the side of the side chain. The main polymer chain EPDM is fully saturated. This feature makes the EPDM is resistant to heat, light, oxygen, especially ozone. EPDM essence is non-polar, resistant to polar solvents and chemicals, bibulous rate is low, has good insulating properties.
In EPDM production process, by changing the number of third monomer, ethylene propylene ratio, molecular weight and its distribution, and the vulcanization method can adjust its characteristics.
Selection of EPDM third monomer
The monomer of the type three two olefin is produced by copolymerization of ethylene and propylene in the polymer, and the choice of the third monomer must satisfy the following requirements:
Up to two keys: one can be polymerized, one can be vulcanized
The reaction is similar to the two basic monomers.
Random aggregation of primary key generates uniform distribution
Sufficient volatility to facilitate removal of the polymer from the polymer
The final cure rate of the polymer is suitable
The industrial production of ethylene propylene rubber with third three yuan only the following three kinds of monomer:
Ethyiidenenorbomene (ENB)
Bis (DCPD)
1,4- (HD) - (-) - (-)
CH3-CH=CH-CH2-CH=CH2
(such a single body is currently only the United States Pont Du company use)
Effect of the type and content of the type of the polymer on the properties of the polymer
Three yuan in the production is mainly used ENB and DCPD.
EPDM in the most widely used is ENB, it than DCPD vulcanized to much faster. Under the same polymerization conditions, the nature of third monomer affects long chain branching and increased in the following order: EPM<EPDM (ENB) <EPDM (DCPD),
Three yuan by third other diene monomer influence and:
ENB- fast curing, high tensile strength, low permanent deformation
DCPD- anti coking, low permanent deformation, low cost
With dienes the third monomer increased, there will be the following effects: faster curing rate, lower compression deformation, high tensile and accelerator selection diversity and minimize the anti coking and extension, higher cost of polymer.
Ethylene propylene ratio
Ethylene propylene ratio can change in the curing process, commercial ternary ethylene propylene polymer ethylene propylene than by the 80 / 20 to 50 / 50. When the ethylene and propylene by 50 / 50 to 80 / 20, a positive impact than: more high strength of green compacts, higher tensile strength, higher crystallization, vitreous lower transformation temperature, polymer raw material into pellets, and better extrusion characteristics. Bad influence is not good rolling mixed, poor low temperature properties, and good compression deformation.
When higher proportion of propylene, the advantage is better processing performance, better low temperature characteristics and better compression deformation and so on.
Molecular weight and molecular weight distribution
The molecular weight of the elastic body usually Mooney viscosity said. In the EPDM Mooney viscosity, these values are obtained at high temperatures, usually 125 DEG C, the main reason for doing so is to eliminate produced by high ethylene content of any effect (crystallization), which will cover up the true molecular weight of the polymer. EPDM Mooney viscosity range between 20 to 100. There is also a higher molecular weight of commercial EPDM also produce, but generally oil filled to mixing.
The molecular weight and the distribution of the three yuan in the polymerization in the polymerization process through the following ways:
Type and concentration of catalyst and Co catalyst
temperature
Modified agent, such as hydrogen concentration
EPDM molecular weight distribution by gel permeation chromatography using dichlorobenzene as solvent at high temperatures (150 DEG C) measuring and. Molecular weight distribution is often referred to as is the ratio of weight average molecular weight and number average molecular weight. According to the common and highly branched structure, the value varies between 2 and 5. Due to the key points, DCPD containing ternary ethylene propylene rubber and wider molecular weight distribution.
By increasing the molecular weight of EPDM, the positive impact: higher tensile and tear strength, under the condition of high temperature higher green strength, can absorb more oil and filler (low cost). With increase of the molecular weight distribution, the positive effects are: increase mixing and milling processing. However, narrow molecular weight distribution can improve the speed of curing, curing condition and injection behavior.
Folding curing type
EPDM can use organic peroxides or sulfur vulcanization. However, compared with sulfur and peroxide crosslinking of EPDM for wire and cable industry has higher temperature resistance, lower compression deformation and improved vulcanization characteristics. Bad place sulfur peroxide is more high cost.
As previously mentioned, EPDM chain speed and curing time with sulfide type and content change. When the EPDM and butyl, natural rubber, styrene butadiene rubber mixing, in the choice of appropriate EPDM products must to take into account the following factors:
When mixed with butyl, because of the low degree of unsaturation butyl, in order to adapt to the butyl curing rate, the best choice is relatively low content of DCPD and ENB content of EPDM.
When compared with natural rubber and styrene butadiene rubber mixing, the best choice of 8% to three yuan 10%ENB content, to meet the curing rate.
EPDM is ethylene, propylene by solution copolymerization of rubber is introduced, and then the third monomer (ENB). EPDM basically is a saturated polymer, aging resistant performance is very good, good weather resistance, excellent electrical insulation properties, resistance to chemical corrosion, impact elasticity better. The main disadvantage of ethylene propylene rubber is curing speed is slow; and other unsaturated rubber and hard to use, self and mutual viscosity is very poor, so processing performance.
According to the characteristics of ethylene propylene rubber, mainly used in the requirements of aging resistance, water resistance, corrosion resistance, electrical insulation in several areas, such as that used for the tire of the light side of the tire, heat resistant conveyor belt, cable, wire, anti-corrosion lining, sealing washers, building waterproof sheet, doors and windows sealing strip, accessories for household electrical appliance, plastic modification. Ethylene propylene rubber properties and uses.
Ethylene propylene rubber to ethylene and propylene as the main raw material synthesis, aging resistance, electrical insulation performance and resistance to ozone generator can highlight. Ethylene propylene rubber can charge a lot of oil and carbon black filled, lower prices of products, ethylene propylene rubber chemical stability, abrasion resistance, elasticity, resistance to oil and styrene butadiene rubber (SBR) close. Ethylene propylene rubber is very versatile can as a tire, rubber strip and tube and car parts, can also used for wire, cable sheathing and high pressure, ultra high pressure insulating materials. Manufacturing and a pair of shoes, sanitary products and other light colored products. Ethylene propylene rubber with improved performance:
One, 1, low density and high filling
The density of ethylene propylene rubber is lower a rubber, its density is 0.87. Coupled with large filling oil and adding filler. Therefore, it can be reduce the cost of rubber products, and make up the shortcoming of the high price of ethylene propylene rubber, and for ethylene propylene rubber Mooney value, high filling after physical and mechanical can reduce greatly.
2, resistance to aging
Ethylene propylene rubber has excellent weather resistance, ozone resistance, heat, acid and alkali resistance, resistance to water vapor, color stability, electrical properties, oily at room temperature and charge mobility. Ethylene propylene rubber products in 120 DEG C can use for a long time, in the 150 to 200 DEG C can be transient or intermittent use. Adding suitable antioxidant can improve the use of temperature. By peroxide crosslinking of EPDM rubber can be used in harsh conditions. EPDM rubber in ozone concentration 50pphm and stretched up to 30% under the condition, can reach 150h above does not crack.
3, corrosion resistance
Due to the lack of polarity of ethylene propylene rubber and low unsaturation, and a variety of polar chemicals such as alcohols, acids, alkalis, oxidation agent, refrigerant, detergent, vegetable oil, ketone and grease has good resistance; but in fat and Fang is a solvent (such as gasoline, benzene) and mineral oil in poor stability. Under the concentrated acid effect of long-term performance will be decreased. In ISO/TO 7620 Zhonghui set the nearly 400 species with corrosive gaseous and liquid chemicals, the role of the rubber performance of the various data, and the provisions of the 1-4 level said the degree of the effect and influence of corrosive chemicals on the properties of rubber:
Level volume swelling /% lower hardness values influence on properties
1 <10 <10 slight or no
2 <20 10-20 smaller
3 <30 30-60 medium
4 >30 >60 serious
4, water vapor resistance
EPDM has excellent resistance to water vapor properties and to estimate is better than the heat resistance. In 230 DEG C superheated steam, nearly after 100h appearance without change. And fluorine rubber, silicone rubber, fluorosilicone rubber, butyl rubber, nitrile rubber, natural rubber under the same conditions, experience a short time appearance deteriorated phenomenon.
5, resistant to hot water performance
Ethylene propylene rubber high water resistance, also good, but is closely related with all vulcanization system. With morpholine disulfide, TMTD ethylene propylene rubber vulcanization system, 125 DEG C hot water to soak for 15 months later, mechanical properties change very little, volume expansion rate is only 0.3%.
6, electrical properties
Ethylene propylene rubber has excellent electrical insulation properties and corona resistance, electric properties are better than or near to styrene butadiene rubber, chlorosulfonated polyethylene, polyethylene and crosslinked polyethylene.
7, flexibility
Due to the molecular structure of ethylene propylene rubber non-polar substituents, molecular cohesion can low, molecular chain can be in a wide range of maintain flexibility, second only to natural discussion and butadiene rubber, and at low temperatures can still maintain.
8, adhesion
The molecular structure of ethylene propylene rubber due to lack of active groups, the cohesive energy is low, and the adhesive material is easy to spray frost, self adhesive and mutual adhesive is poor.
Two, ethylene propylene rubber modified varieties.
Three yuan and three Yuan rubber from the end of 1950s, since the early 60´s successful development of the world and the emergence of a variety of modified ethylene propylene rubber and thermoplastic ethylene propylene rubber (EPDM/PE), which provides a large number of varieties and grades for wide application of EPDM. Modified EPDM is ethylene propylene rubber the bromination, chloride, sulfonation, maleic anhydride, maleic anhydride, silicone modified nylon modified EPDM grafted with acrylonitrile. Also, acrylate. Over the years, by blending, copolymerization, grafting, filling, enhancement and molecular composite polymer materials and other means to obtain many good properties of EPDM. Through the modification, also get great improvement in terms of performance, thus expanding the scope of application of ethylene propylene rubber.
Bromide ethylene propylene rubber is in open smelting machine to by brominating agent processing and. Bromide ethylene propylene rubber can improve the curing rate and adhesion properties, but the decline in mechanical strength and bromide ethylene propylene rubber applies only to the intermediary of ethylene propylene rubber and other rubber adhesive layer.
Chlorinated ethylene propylene rubber is made chlorine by EPDM rubber solution. Chlorinated ethylene propylene rubber can improve the curing rate and discussion with unsaturated compatibility, fire resistance, oil resistance, adhesion properties were also improved.
Sulfonated EPDM is ethylene propylene diene monomer is dissolved in the solvent, from the gum of sulfonating agent and agent. Sulfonated EPDM due to having thermoplastic elastic body physique and good adhesion properties, adhesive, coated fabrics, building waterproof lean meat, anticorrosive lining will be widely used.
Acrylonitrile grafted ethylene propylene rubber with toluene as solvent, benzene chloride in methanol as initiator, in 80 DEG C of acrylonitrile grafted on ethylene propylene rubber acrylonitrile modified ethylene propylene rubber not only retains the ethylene propylene rubber corrosion resistance, and