General Properties
Short Name:
Name:
EPDM
Ethylene-propylene-diene rubber
EPDM is a terpolymer with a diene component, such as cyclopentadiene. E stands for ethylene, P for propylene, D for diene and M for the class of saturated carbon molecules in the main macro-molecule-chain (classifi cation in accordance with ISO 1629 or ASTM D1418). Commercial EPDM rubbers have an ethylene content of approx. 45–75 weight%. Polymers with a low ethylene content (45–55 weight%) are amorphous and very flexible at low temperatures. With an increasing ethylene content, the degree of crystallinity rises. EPDM with a mean ethylene content of approx. 55–65 weight% is semi-crystalline. With ethylene contents >65 weight%, EPDM features larger crystalline regions and behaves as a thermoplastic elastomer.
Structural Formula
Properties
| Glass Transition Temperature | -55 to -30°C |
|---|---|
| Melting Temperature | -20 to 60°C |
| Melting Enthalpy | 5 to 20 J/g |
| Decomposition Temperature | 470 to 487°C |
| Young's Modulus | 2 to 10 MPa |
| Coefficient of Linear Thermal Expansion | 180 *10-6/K |
| Specific Heat Capacity | 1.80 to 2.00 J/(g*K) |
| Thermal Conductivity | 0.26 W/(m*K) |
| Density | 0.86 g/cm³ |
| Morphology | Rubber, sometimes with soft and hard segments |
| General properties | Very good electrical insulating properties. Very good ozone and sunlight resistance. Good aging resistance. Good resistance to heat, chemicals, hot water and water vapor |
| Processing | Cross-linking by means of sulfur (with accelerators) or peroxides |
| Applications | Seals and profiles. Cable sheathings and insulations. Cool water hoses. Components of household appliance. Construction sealing strips. Blend partners in PP-EPDM blends (TPV) to improve the impact strength of PP (application in the automobile industry as underbody or bumper material) |
NETZSCH Measurement
| Instrument | DSC 204 F1 Phoenix® |
| Sample Mass | 13.83 mg |
| Isothermal Phase | 7 min |
| Heating/Colling Rates | 10 K/min |
| Crucible | Al, pierced lid |
| Atmosphere | N2 (40 ml/min) |
Evaluation
This EPDM sample is not purely amorphous since it exhibits a small melting transition at 6°C (peak temperature, 2nd heating, red) with an enthalpy of 0.8 J/g, indicating a small amount of crystalline content. The glass transition at -54°C (midpoint, both heatings) is from the amorphous content. The endothermal effect with peak temperatures of 43°C and 52°C (2nd heating, red) is probably due to the melting of additives. This appears as a single peak in the 1st heating (blue).