Acrylic Elastomers, Survey

AbstractAcrylic elastomers have the ASTM designation ACM for polymers of ethyl acrylate and other acrylates, and ANM for copolymers of ethyl or other acrylates with acrylonitrile. In both cases, the M indicates a polymer having a saturated chain of the polymethylene type. The combination of a saturated backbone with polar side chains results in a class of polymers with very good resistance to heat and oil, including oils containing hypoid additives. Acrylic elastomers also have good resistance to sunlight and ozone. Ethylene–acrylic elastomers are discussed in a separate article.The first acrylic elastomers were homopolymers of either ethyl acrylate or methyl acrylate. Because these had limited utility, particularly for vulcanized applications, various copolymer modifications were developed to improve performance, and there evolved a division of monomers into two types:backbone monomers, which comprise the principal proportion of the monomers and determine the physical and chemical properties of the polymer, andcure‐site monomers, which are incorporated to the extent of 1–5% to introduce reactive sites for subsequent cross‐linking reactions.Emulsion and suspension polymerization are the important methods for preparing the elastomers. Their rheological characteristics require processing that addresses contamination more than for other types. Fairly rigid processing is required. The monomers from which these elastomers are prepared have varying degrees of toxicity. Because of the wide property range, the acylic elastomers have many application, eg, coatings, textiles, automotive products, adhesives, paper, and agriculture.