Views:67 Author:Site Editor Publish Time: 2020-06-23 Origin:Site
Introduction: This article is mainly for everyone's popular EPDM material, what characteristics does it have, and what applications does it have in life.
EPDM is a copolymer of ethylene, propylene, and a small amount of non-conjugated diene. It is a type of ethylene-propylene rubber. It is expressed in EPDM (Ethylene Propylene Diene Monomer) and began commercial production in 1963. The world's annual consumption is 800,000 tons. The most important feature of EPDM is its superior resistance to oxidation, ozone and erosion. Since EPDM belongs to the polyolefin (PO) family, it has excellent vulcanization properties. Among all rubbers, EPDM has the lowest specific gravity, can absorb a large amount of fillers and oils and has little effect on the characteristics, so it can produce rubber compounds with low cost.
The density of ethylene-propylene rubber is a lower 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, make up for the shortcomings of high price of ethylene-propylene rubber raw rubber, and for the high Mooney value of ethylene-propylene rubber, the physical mechanical energy after high filling decreases Not big.
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 ℃, can be used briefly or intermittently at 150-200 ℃. Adding a suitable anti-aging agent can increase its use temperature. The EPDM rubber cross-linked with peroxide can be used under severe conditions.
Due to the lack of polarity and low unsaturation of ethylene-propylene rubber, it has good resistance to various polar chemicals such as alcohols, acids, alkalis, oxidants, refrigerants, detergents, animal and vegetable oils, ketones and fats. But poor stability in fatty and aromatic solvents (such as gasoline, benzene, etc.) and mineral oil. Under the long-term effect of concentrated acid, the performance will also decrease.
Ethylene-propylene rubber 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 hours. However, under the same conditions, fluororubber, silicone rubber, fluorosilicone rubber, butyl rubber, nitrile rubber, and natural rubber experienced significant deterioration in appearance.
Ethylene-propylene rubber also has good resistance to hot water, but it is closely related to all its vulcanization systems. Ethylene propylene rubber with dimorpholine disulfide and TMTD as the vulcanization system, after immersion in superheated water at 125 ℃ for 15 months, the mechanical properties changed very little, and the volume expansion rate was only 0.3%.
Ethylene-propylene rubber has excellent electrical insulation properties and corona resistance, electrical performance is better than or close to styrene-butadiene rubber, chlorosulfonated polyethylene, polyethylene and cross-linked polyethylene.
Because there is no polar substituent in the molecular structure of ethylene-propylene rubber, the molecular cohesive energy is low, and the molecular chain can maintain flexibility in a wide range, second only to natural rubber and cis-butadiene rubber, and can still be maintained at low temperatures.
Due to the lack of active groups in the molecular structure of ethylene propylene rubber, the cohesive energy is low, and the rubber is easy to frost, and the self-adhesion and mutual adhesion are poor.
Compared with other commonly used general rubber or special rubber, the main performance advantages of EPDM rubber are in the following aspects:
(1) High cost performance, raw rubber density is only 0.86 ~ 0.90g/cm3, is the lightest commonly used rubber density; and can be filled in large quantities to reduce the cost of rubber.
(2) Excellent aging resistance, weather resistance, ozone resistance, sunlight resistance, heat resistance, water resistance, water vapor resistance, ultraviolet resistance, radiation resistance and other aging properties, in combination with other unsaturated diene rubbers such as NR, SBR, When BR, NBR, and CR are used together, EPDM can act as a polymer antioxidant or anti-aging agent.
(3) Excellent chemical resistance, acid resistance, alkali resistance, detergent, animal and vegetable oil, alcohol, ketone, etc.; outstanding water resistance, super hot water resistance, steam resistance; polar oil resistance.
(4) Excellent insulation performance, volume resistivity 1016Q·cm, breakdown voltage 30-40MV/m, dielectric constant (1kHz, 20℃) 2.27.
(5) The applicable temperature range is wide, the minimum operating temperature is -40～-60℃, and it can be used under 130℃ for a long time.