What is EPDM rubber?
EPDM (Ethylene Propylene Diene Monomer) a synthetic rubber made from ethylene, propylene, and diene monomer, is commonly used in the automotive and construction industries. Silicone, a man-made material derived from quartz sand, is employed in a wide range of applications, including automotive, aerospace, and food and beverage processing.
In this article, we cover more about this synthetic rubber, including:
What is EPDM rubber used for?
EPDM as a synthetic rubber is an economical alternative to silicone rubber. Silicone rubber can withstand extreme temperatures, is a better electrical insulator, and maintains its shape and resilience better over time. EPDM withstands more chemicals, and as already noted, costs less.
Learn more about EPDM vs. Silicone: A Simple Guide.
Before we look at specific EPDM uses and properties, it helps to put the material in context. EPDM rubber uses are found in these sectors:
| Industry | Why |
|---|---|
| Automotive | Flexibility, resilience, weatherability and oil resistance |
| Industrial | Electrical insulation, water resistance, flexibility and resilience |
| HVACs | Weatherability, temperature resistance and insulation |
| Construction | Insulation, weatherability and water resistance |
EPDM material properties
Specifically, ethylene Propylene Diene Monomer, or EPDM, is a copolymer of ethylene and propylene. It also contains between 3% – 9% non-conjugated diene monomers, which enables crosslinking for rubber hardening, known as vulcanisation. Depending on how it’s formulated, EPDM rubber material properties offer good low-temperature properties, standing up to -50°C.
EPDM properties include fair to excellent tear resistance, depending on how it’s formulated. Its elastic properties, however, is one of its primary attractions. It also has good chemical resistance and withstands temperatures of up to 150°C, while still remaining flexible.
Both natural rubber and EPDM are flexible, but natural rubber can’t stand up to the factors that EPDM rubber can, such as weathering resistance. The molecular structure of EPDM rubber has a single bond, chemically saturated backbone. This is what makes it extremely resistant to the elements. EPDM rubber is perfect for outdoor applications, resisting UV and ozone. With blockers, it can offer good flame resistance.
EPDM rubber properties also provide excellent electrical insulation – which makes it a suitable material for insulating and connecting cables and wires, for instance. It adheres easily to metals, which makes it ideal for seals. It also has excellent resistance to steam and good anti-vibration capabilities.
Disadvantages of EPDM rubbers: they have poor oil resistance and cannot stand up to solvents or hydrocarbon oils. Due to chemical interactions, it also degrades when in contact with bituminous material, such as asphalt shingles.
EPDM mechanical properties
EPDM rubber properties include the following:
| Properties | Value |
|---|---|
| Durometer or Hardness Range | 30 – 90 Shore A |
| Tensile Strength Range | 17 MPa |
| Elongation Range after fracture | ≥ 300% |
| Density | Can be compounded from 0.90 to >2.0 g/cm3 |
| Adhesion to Metal | Good to Excellent |
| Adhesion to Rigid Materials | Good to Excellent |
EPDM thermal properties
EPDM rubber has a fairly low density and the highest heat capacity among rubber materials.
| Property | Value |
|---|---|
| Coefficient of thermal expansion, linear | 160 µm/(m·K) |
| Maximum service temperature | 150°C |
| Minimum service temperature | -50°C |
| Glass transition temperature | −54°C |
EPDM foam properties
EPDM foam is produced by adding a blowing agent to EPDM rubber and then heating the mixture to create a foam. The resulting material has a closed-cell or semi-closed-cell structure that makes it an excellent insulator for both temperature and sound. When you hear the phrase EPDM sponge rubber properties, this is what they’re referring to.
Closed-cell EPDM foam has a tightly packed cell structure that provides excellent insulation and resistance to moisture and water absorption. It’s commonly used for insulation, gaskets, and seals where a high level of insulation or water resistance is required.
Semi-closed-cell EPDM foam has a less tightly packed cell structure, making it more compressible and flexible than closed-cell foam. This type of foam has better shock absorption properties, making it ideal for use in cushioning, gaskets, and seals in applications that require flexibility and shock absorption.
EPDM foam is exceptional for weather stripping. An excellent example is shown here. Closed-cell EPDM foam weather-stripping and gasket tape provides superb barrier protection from moisture and air. These tapes offer outstanding resistance to water absorption, ozone and UV ageing.
EPDM rubber applications
Specifically, what is EPDM rubber used for? Masking solutions are a typical application.
Easy-pull masking cap
EPDM can stand up to the temperatures that masking demands. The easy-pull masking cap here features a wide flange that provides a positive seal and makes removal easy. The internal seal prevents ingress. The ribbed design means that it fits a range of sizes. Reusable. Ideal applications include anodising, blasting, powder coating, e-coating, and plating.
PCB supports
Another EPDM application includes PCB supports. Pull mount ends locked into position, once fed into their holes. The ends are then easily cut off, leaving low profile mounting ends. EPDM is an ideal material for PCBs due to the electrical insulation they provide.
Stepped grommets
Other examples of EPDM rubber uses: Stepped grommets, also called angular hole grommets – allow a wire to pass through a panel at a maximum angle of 45 degrees.
Sealing grommets
You can also get sealing grommets rated IP67, which means They provide a watertight and dust seal and are perfect for outdoor applications. They’re designed to withstand vibration, making it ideal for external enclosures. You can also use them as blanking plugs until your cables are installed.
You can learn more in our Guide to Rubber Grommets.
Clip-on profiles
Clip-on profiles are a type of bubble gasket for enclosure boxes. The edge and trim seal is ideal for EMI shielding and protection.
EPDM automotive applications
Heat resistance is critical to the automotive industry, which makes EPDM rubber invaluable. EPDM automotive applications include bonnet seals, hose material, oil coolers, boot seals, cooling system circuit hoses, radiator and heater hoses, window seals, door seals, and more.
Open grommet
This snap-fit design of this open grommet enables quick and easy installation, which helps with the production process.
Also popular is gasket with an adhesive backing. It’s ideal for sealing applications like door seals and window seals for weather stripping.
EPDM gasket properties
Why is EPDM so popular for gaskets? There are similar materials used for this application, such as TPR and TPE. Both have unique advantages, but neither matches EPDM for weather resistance. So if your EPDM gaskets are intended for outdoor use, there’s no comparison.
Learn more in our guide, Seals and Gaskets explained.
EPDM o-ring properties
EPDM o-ring material properties are that of EPDM rubber, which makes this application highly elastic. It can be stretched and compressed repeatedly without losing its shape or mechanical properties. This flexibility allows EPDM o-rings to provide a tight and secure seal even in applications where there is movement, vibration or pressure variations.
You can find out more in our Guide to O-ring Seals.
EPDM membrane application
EPDM rubber is used as membranes in roofing material. The reason is attributed to their exceptional weather resistance, UV stability, and flexibility. Installation is easy, and its long-term durability make it ideal for roofing systems.
EPDM membranes create a reliable barrier against water, moisture, and other environmental factors that can cause damage to the roof and affect its structural integrity. EPDM membranes are also used in other waterproofing applications, such as pond and pool liners, and foundation waterproofing.
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