Vamac® Grade Selection
Vamac® Grade Selection and Performance Information
Several grades of DuPont™ 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:
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.
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. The low swell grade exhibits about one half the IRM903 oil swell of its Vamac® 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® 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. Mechanical properties, tear strength and heat resistance are further improved with Vamac® Ultra HT. Higher viscosity of Ultra HT improves processability, and provides higher green strength versus Vamac® G or GXF.
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 or Ultra IP should be considered. Vamac® Ultra IP improves performance and productivity. The higher viscosity of Ultra IP permits better and faster dispersion of fillers and other compound ingredients, especially for low hardness compounds or in compounds with high plasticizer levels. Ultra IP also improves productivity with lower mold fouling.
As sold, all gum Vamac® contains a small amount of release agent, required for processing. Please feel free to contact DuPont for technical assistance as you optimize your formulations to meet specific performance needs or business proprietary requirements.