1、Introduction of ethylene acrylate rubber (AEM)
Acrylated ethylene rubber (AEM) was invented and commercialized by DuPont in 1975, with Vamac® as its trademark. It was invented to meet the automotive industry's need for higher temperature and oil resistance while being cost-effective. Today, AEM is used in a wide range of automotive piping and sealing applications, including turbocharger lines, oil cooler lines, air intake lines, fuel lines, power steering lines, sensor lines, torsion dampers, oil seals, oil pan gaskets and valve cover gaskets.
After more than 40 years of development, AEM now has more than 10 grades with different properties to meet the specific needs of different applications. Common AEM grades can be used for long periods of time in temperatures ranging from -40 to 170 degrees Celsius, while offering excellent oil resistance and compression set properties. As the engine temperature rises and the environmental media become more demanding, AEM is gradually replacing NBR, ECO, ACM and other rubbers in many applications and sales are increasing.
2、Automotive market development trend
In order to meet the requirements of laws and regulations on automotive fuel economy and exhaust emissions, the automotive industry is trying to adopt different technologies to cope with, including automotive lightweight, engine displacement miniaturization, exhaust gas turbocharging technology, direct fuel injection, biofuel, exhaust gas recirculation system (EGR), more efficient transmission, low-viscosity lubricants and so on. In particular, the combination of exhaust gas turbocharging and direct fuel injection technology can reduce engine displacement and increase fuel efficiency without sacrificing engine performance, which is becoming more and more widely adopted in newly developed fuel engines.
(1) Turbocharging systems increase the temperature around the automobile engine;
(2) Low-viscosity fully synthetic lubricants are more aggressive to sealing materials through the addition of more new additives without reducing anti-wear and anti-pressure performance; at the same time, the reduction in viscosity has become more demanding on the sealing ability of the seals;
(3) The exhaust gas recirculation system (EGR) makes more acidic media (usually including organic and inorganic acids, such as formic acid, acetic acid, sulfuric acid, nitric acid, etc.) in the exhaust gas enter into the air intake system, which puts forward new acid-resistant requirements for all kinds of pipelines and sealing materials in the air intake system. The pH value of acidic media is also decreasing continuously, and has now reached the level of pH=1.
3、Performance characteristics of AEM
Ethylene acrylate rubber (AEM) has a good balance of heat resistance, low temperature performance and lubricant resistance.
The performance characteristics of AEM are as follows:
(1) AEM oil resistance and acid resistance performance
Ethylene acrylate rubber (AEM) has good resistance to lubricants, but we often see some standards refer to reference oils as test oils, without using actual lubricants for testing. We found that the data results of the reference oil test can not be used as reference, not to mention that it can not replace the actual oil test, and the test data of the reference oil and the actual lubricating oil are very different.
(2) Heat aging resistance
AEM can be used continuously for 18 months at 120°C and 6 weeks at 170°C, as measured by a 50% reduction in elongation at break, and its heat aging resistance is much better than that of chlorosulfonated polyethylene rubber (CSM) and NBR.
(3) Liquid Resistance
AEM has good resistance to ATF (automobile automatic steering fluid), gear oil, glycol/water mixture, diesel fuel and kerosene, etc., but the resistance to fuel C, phosphate ester hydraulic oil, non-mineral brake fluid, ester, ketone and gasoline is poor.
(4) Cold resistance
AEM's cold resistance is better than ACM, can be used at -40 ℃, if you add the appropriate plasticizer, at lower temperatures can also remain soft.
(5) Compression set resistance
The use of amine vulcanizing agent vulcanized AEM three-dimensional rubber compression permanent deformation resistance is excellent, at 170 ℃ × 70h conditions, compression permanent deformation is less than 20%, but the use of peroxide vulcanized binary rubber compression permanent deformation resistance is slightly worse. Long-term compression permanent deformation test shows that the AEM compression permanent deformation performance is excellent, three-dimensional rubber compression permanent deformation performance and HNBR comparable.
(6) AEM's ozone resistance is excellent, weathering performance is also very good. After 3 years of exposure to the sun, the appearance and physical properties are almost unchanged.AEM ternary rubber has excellent flexural performance, the flexural life is more than 250,000 times at 100 ℃, but the flexural performance of binary rubber is a little worse. Add aluminum hydroxide AEM combustion safety performance is better, especially when combustion smoke and corrosive gas release is very low.AEM dynamic performance is also better, high temperature vibration damping performance and IIR close.
Due to the excellent performance of AEM, it is listed in ASTM D 2000 "automotive rubber products grading system", designated as EE material, EE material refers to the heat-resistant level is 175 ℃, in 150 ℃ IRM 903 # oil (original use of 3 # standard oil) in the immersion of the volume change rate of not more than 80% of the material after 70h. At the same time AEM included in the SAE J200 standard, indicating that AEM has been recognized in the field of U.S. auto parts.
4、Difference between ACM and AEM
The positioning of acrylate rubber cost-effective, hot oil environment effect and fluorine rubber is almost the same. In the nitrile rubber can not meet the requirements, and at the same time do not want to use expensive fluorine rubber used in the case. However, its processing performance is poor, and there are many problems.
Compared with AEM, ACM has many defects such as difficult processing problems, low temperature resistance, and poor compression set. The upgraded version of acrylate rubber: AEM rubber, to make up for these defects, AEM's processing performance and high and low temperature resistance performance than ACM to improve, while the price is also increased a lot!
5、AEM products market application
AEM's application field is mainly automobile parts, such as front and rear crankshaft oil seals, front and rear main shaft oil seals, power steering pump seals, transmission pump seals, water pump seals, engine valve stem oil seals, CVJ dust cover and power steering hoses and 175℃ grade radiator hoses. In addition, AEM has better application prospects in the field of halogen-free and low-smoke flame-retardant cable sheathing.
In order to meet the requirements of higher fuel economy and emission regulations, the automotive industry commonly adopts technologies such as turbocharging, direct injection and exhaust gas recirculation (EGR), which leads to higher temperatures in automotive engines, lubricants become harsher, viscosity becomes lower, and the content of acidic media becomes higher. Acrylated ethylene monomer (AEM) rubber, which is used in harsher environments and temperatures, has broadened the performance of AEM and expanded the range of applications for which AEM can be used. More and more products are using AEM, AEM rubber is tighter and prices are rising! Translated with www.DeepL.com/Translator (free version)