A Complete Guide to EPDM Rubber

Ethylene-propylene diene monomer (EPDM) is one of the most common and widely used man-made synthetic rubber materials. It is available as a solid or closed-cell sponge in a range of hardnesses and densities. It has an excellent resistance to weathering, ozone and chemicals.

EPDM has taken its place as the preferred rubber compound for manufacturing rubber seals for almost every industry sector. With over 70% of the material used for manufacturing rubber products being synthetic, the largest proportion of this is EPDM. Its global success and mass production has resulted in an incredibly versatile and low cost compound suitable for almost any application.

This guide provides a background to the history of EPDM and explains the main advantages and disadvantages of using it to manufacture custom seals, trims and gaskets.

EPDM is a reliable general purpose material that is commonly used to manufacture a range of rubber sealing products. Exhibiting an excellent resistance to the effects of weathering and being a low-cost mass produced rubber compound, EPDM is often the preferred material for outdoor sealing applications. Some of the key advantages of EPDM rubber include;

• Weathering: As EPDM can withstand exposure to the elements, it is suitable for seals, trims and gaskets manufactured for the outdoor environment. This ability makes EPDM highly resistant to weathering, ozone and UV when exposed to direct sunlight. Rubber seals manufactured from EPDM, in both their sponge and solid forms, also demonstrate outstanding water resistance and are impermeable to moisture.
  
  
• Temperature Range: Operating within a temperature range of -40°C to +120°C without deforming, cracking or splitting, EPDM performs well in low and high temperature environments. This material offers excellent performance by remaining stable and staying the same hardness all year round.
  
  
• Chemical Resistance: EPDM exhibits a very good resistance to a wide range of chemicals, including acids and alkaline solutions so is suitable for use within environments where exposure to these substances is likely.

As well as offering an excellent resistance to weathering and chemicals, EPDM demonstrates further functional characteristics that make it an ideal material for most rubber sealing applications. These characteristics include;

• Durability: In comparison to natural and some other synthetic rubber compounds, EPDM is known for its durability and resistance to tearing and abrasion. Expanded EPDM rubber seals do not easily stretch so are unlikely to be damaged during installation and can be repeatedly compressed by approximately a third without the risk of compression set.
  
  
• Cost Effective: EPDM is the base material for the majority of synthetic rubber products for the marine, automotive and construction industries. The mass production of this rubber compound allows seals manufactured in EPDM to be produced at a lower cost than those made from other similar materials. As rubber sealing products manufactured from EPDM are strong, hardwearing and resistant to abrasion, they need to be less frequently replaced. The initial low production cost together with the materials resilience makes EPDM an affordable option for most sealing projects.
  
  
• Closed-Cell: During manufacturing, gases can be injected into the rubber compound to make expanded EPDM. This is a closed-cell compressible material that does not absorb water and can be used to create watertight seals on hatches, doors and lockers. In the same way as solid EPDM, expanded EPDM can be cut or extruded into an endless variety of shapes and sizes.
  
  
• Hybrid Compounds: It is possible to blend expanded EPDM with other expanded materials, such as Nitrile and Neoprene, to make hybrid compounds with increased chemical resistance or reduced costs. By itself, expanded EPDM should not come into contact with large amounts of oil. However, combining this material with expanded Nitrile creates a blended material that will not degrade with oil exposure.
  
  
• Vibration and Sound Damping: The elasticity and flexibility of EPDM make it effective in reducing noise transmission and dampening vibrations or shock. This allows the rubber to be used in automotive components and industrial machinery.

Although EPDM is the material of choice for most sealing applications, there are occasions where alternative rubber compounds, such as Silicone or Nitrile, would be better suited. Some of the drawbacks include;

• Oil Resistance: EPDM rubber seals are not suitable for applications that involve exposure to petroleum-based oils and fuels. Constant contact will cause the rubber to break down, swell and lose its mechanical properties. Nitrile has similar characteristics to EPDM, such as excellent weathering and chemical resistance, but will not degrade if exposed to oil or fuel.
  
  
• Extreme Temperatures: Although EPDM performs well across a -40°C to +120°C temperature range, it is unsuitable for freezer cabinets, ovens and autoclaves that go outside of this temperature range. Sealing solutions that will be used in extreme temperatures should be manufactured from high temperature resistant materials like Silicone. Silicone can withstand significantly lower and higher temperatures between -50°C to +200°C.

EPDM rubber is available in a diverse range of grades and hardnesses suitable for different industries and applications. As a material that can be cut or extruded in both sponge and solid variants, EPDM offers a solution to most sealing applications. During manufacture, EPDM can be blended with other rubber compounds, such as Nitrile, to increase the compounds resistance to oil and fuel.