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