Ethylene acrylic rubber

Ethylene acrylic rubber is a ethylene-methyl acrylate polymer with a small amount of monomer containing carboxylic acid groups. AEM is resistant to heat, chemicals, ozone and oil and offers good resistance to lubricating oils and greases (even those containing aggressive additives) and to power steering and transmission fluids.

AEM rubber is also known under the trade name Vamac®. It is slightly more heat-resistant than ACM (polyacrylate rubber) and has greater strength. However, its resistance to mineral oils is generally inferior.

This rubber is preferably used in parts of air management systems and in powertrains. It provides long-term resistance even under the influence of diverse chemicals and additives, across a broad temperature range.

AEM rubber is widely used in the automotive sector, for example for hose applications, engine and transmission seals and in turbocharger components. Transmission and engine seals made from AEM are resistant to lubricants and fluids, even those containing a high proportion of additives, and they retain their sealing properties even under pressure. Examples of their use include cylinder head cover gaskets.

Polymer characteristics of ethylene acrylic rubber

AEM rubbers were introduced into the market by DuPont in 1975 under the trade name Vamac. Ethylene acrylic rubber is a mixed polymer of ethylene and methyl acrylate, with the addition of a small amount of a carboxylated crosslinking monomer. The combination of ethylene and methyl acrylate gives the rubber its excellent thermal stability, while its resistance to media such as oils and fats is due to the polarity of the methyl acrylate comonomer. These properties are determined by the ratio of the two comonomers. A higher acrylate content improves resistance to oils, but reduces low-temperature flexibility.

Compound formulation and processing of AEM rubber

In terms of compound formulation, there is no significant difference between the polyethylene acrylate elastomer and ACM rubber. Terpolymers are crosslinked via diamines, whereas peroxides in combination with coagents are used for copolymers.

Properties of ethylene acrylic rubber

AEM is resistant to oil, heat and ozone. In addition, AEM has good resistance to lubricating oils and greases (based on synthetic or mineral oils with aggressive additives) and to transmission/power steering fluids. Polyethylene acrylate elastomer is more heat resistant than polyacrylate rubber (ACM) and it also has better strength and low-temperature flexibility. AEM rubbers are not resistant to aromatic hydrocarbons, esters, ketones and concentrated acids. AEM elastomers offer excellent damping properties over a broad temperature range. As AEM rubbers are free from halogen, mixes can also be used to produce flame-retardant cables, floor coverings or seals.

Properties of AEM rubber at a glance:

  • Excellent weather and ozone resistance
  • Very good heat and chemical resistance
  • Resistant to most oils and lubricants (even those containing aggressive additives)
  • Low compression set
  • Good for low-temperature applications
  • Thermal application range: -40 to +150°C, up to 175°C for short periods

Polyethylene acrylate elastomers are fully compliant with the latest standards. For that reason, most car manufacturers worldwide use them to produce engine-related components, including:

  • Turbocharger hoses and other hose applications
  • Blow-by gas and diesel particle filter sensor sheaths
  • Air management elements
  • Oil- and heat-resistant vibration dampers
  • Engine and transmission seals
  • Cylinder head cover gaskets
  • Oil filter and oil sump gaskets
  • Shift pistons
Rolf Müller
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