Vamac ethylene-acrylic elastomers

Vamac Ethylene-acrylic elastomer, curable with diamines E. I. du Pont de Nemours Co. 

Commercial Forms. Four different base polsrmers of Vamac ethylene-acrylic elastomers are commercially available (Table 1). Until 1990, existing grades of ethylene-acrylic elastomers were based on a single-gum polymer, Vamac G, defined as a terpolymer of 55% methyl acrylate, ethylene, and a cure-site monomer (6). In 1991, a higher methyl acrylate terpolymer, Vamac GLS, was introduced. The composition of this polymer was specifically chosen because it significantly increased the oil resistance of the polymer while minimizing the loss in low temperature flexibility (7). 

Table 1. Vamac Ethylene-Acrylic Elastomer Polymers...

H. J. Barager and L. C. Muschiatti, Vamac Ethylene Acrylic Elastomers for Demanding Automotive Applications, Paper No. 189, American Chemical Society Rubber Division, Orlando, Fla., Sept. 1999. 

C. Williams, Vamac Ethylene/Acrylic Elastomer, A Survey of Properties, Compounding and Processing, Bulletin H-34753, DuPont Polymers, Stow, Ohio, Jan. 1992. 

FIGURE 6.1 Stmctures of Vamac ethylene acrylic elastomers. 

Terpolymers in which the acrylate monomer is the major component are useful as ethylene-acrylate elastomers (trade name Vamac) [Hagman and Crary, 1985]. A small amount of an alkenoic acid is present to introduce sites (C=C) for subsequent crosslinking via reaction with primary diamines (Sec. 9-2d). These elastomers have excellent oil resistance and stability over a wide temperature range (—50 to 200°C). They are superior to nitrile and chloroprene rubbers. Although not superior to silicone and fluorocarbon elastomers, they are less costly uses include automotive (hydraulic system seals, hoses) and wire and cable insulation. 

Ethylene acrylic elastomer (Vamac G) Irganox 1010 Zinc borate... 

J. F. Hagman, Vamac G Gum Ethylene/Acrylic Elastomer, Bulletin E-52096, DuPont Polsmiers, Stow, Ohio, Sept. 1978. 

W.M. Stahl, Fluid resistance of Vamac . DuPont Technical Bulletin EA-510.1 (R2). A.E. Hirsch and R.J. Boyce. Dynamic properties of ethylene/acrylic elastomer A new heat resistant rubber. Proceedings of the International Rubber Conference, Brighton, England, May 1997. DuPont Technical Bulletin C-EA-53C.G04. 

Struktol WB 42 at a 1 % level, combined with 1 % stearic acid, is a good combination for general purpose use in peroxide-cured AEM ethylene acrylic elastomer compounds. Vamac AEM stocks using hexamethylene diamine carbamate (Diak No. 1) as the curative, requires 1% stearic acid plus 0.3% of a stearamide such as Armeen 18D from Akzo and 0.8% of Struktol WS 180. These chemicals act as coagents for mill release. Struktol WB 42, Struktol WS 180, and Armeen 18D also serve as mold release agents. 

Source D.A. Kotz, T.M. Dobel. Stress relaxation of ethylene/acrylic and other gasket materials in automotive fluids. Society of Automotive Engineers International Congress and Exposition, Detroit, Michigan, February/March 1994, Paper No. 940959 Basic principles for the conqtounding and processing of Vamac dipolymers. Dufont Dow Elastomers Technical Information Bulletin H-68560. 

Toughened cyanoacrylate adhesives containing random copolymeric elastomers have been patented. The only elastomer whose performance has been quantified is an ethylene-methyl acrylate copolymer sold by Du Pont under the name Vamac B-124. Several other elastomers are said to be useful tougheners, but no details have been given beyond solubility data. 

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