Ethylene Propylene Rubber (EPM, EPDM)

EPDM O Rings
EPM is a Copolymer of ethylene and propylene. EPDM is a terpolymer of ethylene and propylene with a small amount of a third monomer (usually a diolefin) to permit vulcanization with sulfur. Generally Ethylene Propylene Rubber posses excellent resistance to ozone, sunlight and weathering, and has very good flexibility at low temperature, good chemical resistance (many dilute acids, alkalis & polar solvents), and good electrical insulation properties.

Service Temperature

For EPDM the service temperature can be designed from -55° C to 125° C or up to 150° C (for peroxide cured systems).


40 to 90 Shore A are available.


Black, brown, green, white, rust, yellow, blue, red, orange, purple and gray are available, in addition to customer-assigned colors.


Ethylene Propylene Rubber (EPM) is a good choice for sealing parts in phosphate ester-based hydraulic fluids and glycol based brake fluid systems. EPDM is also is usually used in hot water or steam applications up to 150° C.

Ethylene Propylene Rubber is not suitable in petroleum fluids (fuels, mineral oils, greases)

EPDM O-Rings Material

EPDM-O Rings come in a variety of different formulas. The EPDM O-ring compound we supply at Allied Metric is ethylene-propylene rubber, which is a copolymer; however, we make our EPDM a terpolymer by adding a small amount of a third monomer, which allows the material to vulcanize with sulfur.

Many industries rely on EPDM O-rings for their inherent flexibility, durability, and resistance to potentially destructive environments. They are effective electrical insulators and have an extremely long shelf life. EPDMs can also be formulated with only “white list” ingredients as specified in 21.CFR 177.2600 for use in applications where the elastomer will be in contact with food or beverages. 

Properties of EPDM O-Rings 

EPDM O-rings are popular industrial sealants because of their resistance to water, heat, and steam. They also work well in oxygenated settings and when exposed to mild acid solvents, alkalis, ozone gases, and ultraviolet (UV) rays. They can withstand brake fluid, Skydrol™, and other hydraulic fluids. As a result, EPDM O-rings are essential in the automotive and aviation industries. However, EPDM compounds are not suitable for petroleum, gas, oil, grease, and hydrocarbon environments. The standard temperature range for EPDM O-rings is between -57°F and 257°F.

Specialty EPDM compounds offer different properties. These include:

  • EPDM Sulfur-Cured: This material is inexpensive, readily available, more commercially attractive, and has a higher tensile and tear strength than standard EPDM compounds. It’s used in a wide range of filters and has a maximum operating temperature of 250°F.
  • EPDM Peroxide-Cured: These O-rings are strong and will not stain PVC or metal. They can be used in systems that feature hot water, steam, ketones, alcohols, coolants, acids, and bases, whether they’re organic or inorganic. However, they’re not resistant to mineral oil, grease, or fuel, and have a maximum operating temperature of 300°F.

For use in drinking water applications, EPDMs can be submitted for approval by the National Sanitation Foundation (NSF). They are usually used in automotive air conditioning systems where R134a refrigerant gas and POE or PAG lubricant and new refrigerant for environment protection when R744 is used. In an R744 air conditioning system, it requires excellent resistance to explosive decompression in hydrogen dioxide at high pressure and high temperatures. EPDMs are also used in phosphate ester type hydraulic fluids.

Chemical Resistance of EPDM O-Rings

EPDM O-rings have additional features that make them useful, including their resistance to the following elements:

  • Hot water and steam, up to 300°F (or 600°F with a specialty compound)
  • Glycol-based brake fluid in an environment that’s up to 300°F
  • Cleaning agents, potassium, and soda alkalis
  • Organic and inorganic acids
  • Phosphate-ester hydraulic fluid
  • Many polar solvents
  • Silicone, oil, and grease
  • Aging
  • Exposure to weather and ozone gasses

EPDM O-Rings at Allied Metrics O-Rings & Seals

EPDM O-rings provide superior sealant capabilities and are highly resistant to a variety of conditions. At Allied Metrics, we’ve designed and manufactured high-quality oil seals, hydraulic seals, and pneumatic seals since 1989. We offer many different types of O-rings, and our team will work diligently to find the perfect material to fit your business’ needs. 

Our core value at Allied Metrics is to provide inexpensive, high-quality seals and exceptional customer service. We are proud to say our seals and fasteners empower industries around the world. Visit our website to learn more about Allied Metrics and why our service is right for your business. To learn about pricing, request a quote today.