Several grades of Vamac® ethylene acrylic elastomer are available to rubber compounders and part fabricators. Proper grade selection often depends on a combination of factors, including the following: Vamac® Grades   Product Grade ML(1+4) at 100°C Key Feature   Vamac® G 16.5 Base grade   Vamac® GLS 18.5 Low oil swell   Vamac® HVG 26.0 High viscosity   Vamac® GXF 17.5 High temp performance   Vamac® DP 22.0 No post cure   Vamac® Ultra LT 11.0 Low temp   Vamac® Ultra IP 29.0 Improved performance grade for molding and extrusion Curing method The diamine-cured terpolymer, Vamac® G, is the polymer of choice for most applications. If a postcure is impractical or not desired, then the peroxide-cured dipolymer, Vamac® DP, can be used.

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Basic heat and oil swell characteristics

Compounds based on Vamac® G and Vamac® DP typically exhibit IRM903 oil swell of 50% to 60%. If compounded appropriately, the polymer can withstand 6 weeks of continuous use at 175°C (347°F), maintaining 50 percent elongation. Vamac® is generally assigned an ASTMD2000/SAE200 rating of EG or EF.

For reduced oil swell

For reduced oil swell, DuPont offers Vamac® GLS, a low swell grade of its Vamac® G polymer. The low swell grade exhibits about one half the IRM903 oil swell of its G counterpart. However, its lower oil swell is accompanied by a reduction (by 7°C to 10°C) in low-temperature flexibility.

For low-temperature flexibility

Vamac® Ultra LT has low-temperature flexibility down to -40°C and lower. Vamac® G and Vamac® DP have glass transition temperatures in the range of -30°C (-22°F) to -35°C (-31°F). Vamac® can be compounded to remain flexible in the range of -25°C (-13°F) to -55°C (-67°F), depending on the range of properties desired. The low-swell grade (Vamac® GLS) has slightly higher glass transition temperatures than Vamac® G, resulting in a low-temperature flexibility range of -15°C (5°F) to -45°C (-49°F).

For high temperature performance

Compounds with Vamac® GXF have improved tensile properties and dynamic fatigue resistance at elevated temperatures compared to Vamac® G. At 150°C, tensile strength and ultimate elongation are 12% higher and DeMattia fatigue results show over a 150% improvement. Cure times for Vamac® GXF are slightly longer and compression sets higher than Vamac® G.

For molding or extrusion

Because of their low viscosity, both Vamac® G and DP types are well suited for molding, especially injection and transfer molding. If higher green strength is required, as is the case in most extrusion applications, then blends of Vamac® G with the higher-viscosity Vamac® HVG should be considered.

Compounding considerations

Vamac® Ultra IP improves performance and productivity. As sold, all gum Vamac® contains a small amount of release agent, required for processing.Please feel free to contact DuPont Performance Elastomers for technical assistance as you optimize your formulations to meet specific performance needs or business proprietary requirements.