ACM - Polyacrylic Rubber

Clwyd reference ACM
ASTM classification ACM

Polyacrylic elastomers, also called ACM rubbers / Polyacrylic Rubber, are synthetic elastomers composed of acrylic monomers. These polymers are usually prepared by emulsion or suspension polymerization. The main repeat units are ethyl and butyl acrylate or a blend of both. Many other monomers can be included which allows for a wide variation of the thermophysical and mechanical properties. Very common is the addition of 5 percent 2-chloroethyl vinyl ether.

The combination of a saturated backbone with polar side groups results in a class of polymers with outstanding resistance to heat, oxidation and hydraulic oils. ACM’s also have good resistance to ozone, and weathering which is superior to nitrile rubber. However, water and moisture resistance is poor, as is resistance to acids and alkalis. Furthermore, low temperature applications are usually limited to approximately -10°C due to low cold temperature flexibility and compression set.

Various copolymer modifications have been developed to improve the properties of ACM’s. The modifications include other backbone monomers and the incorporation of reactive site groups (1-5 %) for subsequent crosslinking.

Typical applications

ACM elastomers are primarily used where combined resistance to heat and oils is required. They are often a good alternative to more expensive heat resistant elastomers such as fluorocarbon polymers (FKM), silicones (VMQ) and fluorosilicones (FVMQ) for elevated temperature applications (< 150 °C).

Typical applications include automotive transmission components like seals and hoses that have to be resistant to hot oil, fuel and many other common automotive lubricants and hydraulic fluids. ACM elastomer have also found use in vibration damping due to its excellent resilience. Other applications include textiles, adhesives, and coatings.

The typical continuous service temperature range is -10°C to 150°C (up to 175°C for limited periods of time).

Advantages

Excellent resistance to petroleum fuel and oil

Good heat resistance

Good ozone resistance

Resists flex cracking

Disadvantages

Moderate water resistance

Available hardness range (Shore A) 25 - 85
Upper continuous service temp. 175°C
Min. temp. for sealing applications -60°C
Minimum non-brittle  temp.  -60°C
Tensile strength (up to) 20 MPa
Elongation at break (up to) 450%
Price Bracket Low
ASTM 1 Oil Good
ASTM 2 Oil Good
ASTM 3 Oil Good
Kerosene Excellent
Liquid B None
Liquid 101 None
Phosphate ester None
Ketone None
Toluene None
Iso-octane None
Methanol None
Acid (weak) Good
Acid (strong) None
Base (weak) None
Base (strong) None
Hydrogen sulphide None
Steam None
Ozone Excellent
Radiation Good
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