What is the difference between EPDM and EPR?

EPDM (Ethylene Propylene Diene Monomer) and EPR (Ethylene Propylene Rubber) are both types of synthetic rubber, but they have distinct differences:



EPDM (Ethylene Propylene Diene Monomer)

Composition: Made from ethylene, propylene, and a diene monomer.
Weather Resistance: Exceptional resistance to weathering, ozone, and UV radiation.
Temperature Range: Can withstand temperatures typically from -50°C to 150°C.
Applications: Commonly used in roofing membranes, automotive seals, weatherstripping, and outdoor applications.
Electrical Properties: Good electrical insulation properties.

EPR (Ethylene Propylene Rubber)

Composition: Made from ethylene and propylene without the diene monomer.
Flexibility: Higher flexibility and better low-temperature performance compared to EPDM.
Temperature Range: Good temperature resistance, generally slightly lower than EPDM.
Applications: Often used in electrical insulation, gaskets, and seals in refrigeration systems.
Electrical Properties: Excellent electrical insulation properties.

Key Differences

Chemical Structure: EPDM contains a diene monomer, which allows for cross-linking during vulcanization, enhancing its durability and resistance to heat, ozone, and weathering. EPR lacks this diene monomer, making it more flexible and suitable for low-temperature applications.

Applications: EPDM is preferred for outdoor applications due to its superior weather resistance, while EPR is favored in electrical and refrigeration applications due to its flexibility and insulation properties.

EPDM (Ethylene Propylene Diene Monomer) Rubber Formulation:
Base Polymer:



Ethylene Propylene Diene Monomer (EPDM): 100 parts

Fillers:
Carbon Black: 50-100 parts
Calcium Carbonate: 0-50 parts

Plasticizers:

Paraffinic Oil: 10-30 parts
Naphthenic Oil: 0-20 parts

Curing Agents:
Sulfur: 1-2 parts
Peroxide (if using peroxide curing): 2-5 parts

Accelerators:
Thiazoles: 0.5-1.5 parts
Sulfenamides: 0.5-1.5 parts

Stabilizers:

Antioxidants: 1-3 parts
Antiozonants: 1-3 parts



EPR (Ethylene Propylene Rubber) Formulation:
Base Polymer:



Ethylene Propylene Rubber (EPR): 100 parts

Fillers:

Silica: 30-70 parts
Carbon Black: 20-80 parts
Clay: 0-50 parts

Plasticizers:

Mineral Oil: 5-25 parts
Phthalates: 0-10 parts

Curing Agents:

Peroxide: 2-5 parts

Stabilizers:

UV Stabilizers: 1-2 parts
Antioxidants: 1-3 parts

Combining these monomers forms the polymer chain for EPDM

      H      H              H
      |      |              |
  H — C = C — C — C = C — C — C — C — Diene
      |      |              |
      H      H              H

    (Ethylene)        (Propylene)      (Diene)


Parts :

Ethylene (CH2=CH2):

  H      H      H      H      H      H      H      H
  |      |      |      |      |      |      |      |
H—C—C—C—C—C—C—C—C—C—C—C—C—C—C—C—C—C—C—C—C
  |      |      |      |      |      |      |      |
  H      H      H      H      H      H      H      H


Propylene (CH2=CH-CH3):

    H      H
    |      |
    C = C
    |      |
    H      H

Diene (Third Monomer): Commonly used dienes include:

    H      H
    |      |
    C = C — C — H
    |      |
    H      H


Ethylidene norbornene (ENB)

Dicyclopentadiene (DCPD)

1,4-Hexadiene

Here's a more detailed schematic for a section of an EPR chain:


    H      H      H      H      H      H      H
    |      |      |      |      |      |      |
H — C — C — C — C — C — C — C — C — C — C — C — C — H
    |      |      |      |      |      |      |
    H      H      H      H      H      H      H
(Ethylene) (Propylene) (Ethylene) (Propylene)


Parts :

Ethylene (CH2=CH2):

    H      H
    |      |
    C = C
    |      |
    H      H

Propylene (CH2=CH-CH3):

    H      H
    |      |
    C = C — C
    |      |    H
    H      H