5.5 minutes | 14 Jan 2019
Both are rubbers and both are sometimes confused with one another. What’s the difference between EPDM and Silicone and when should you use one over the other?
First, the basics. EPDM stands for Ethylene Propylene Diene Monomer. It’s a synthetic rubber popular in automotive and construction industries. Silicone, as Polydimethylsiloxane is commonly called, is an inorganic polymer, and based on quartz sand. It’s used in applications that range from automotive and aerospace to food and beverage.
It’s easy to see why there’s some confusion. Both EPDM and silicone:
That’s where their similarities end, however. Let’s take a look at the advantages that each material offers.
EPDM has a stable, saturated polymer backbone structure, which gives the material its advantages.
Of all the rubbers, EPDM is the most water resistant, which is why it’s so popular for outdoor applications and is often used as a roofing material. EPDM stands up to harsh weather conditions such as sleet and snow.
Another reason for its use outdoors, particularly in construction, is its excellent resistance to abrasions and tears and ability to stand up to the degrading effects of weathering, ozone and UV ray exposure.
EPDM also offers good electrical resistance. Its chemical properties make it especially suitable for electrical insulation and gaskets. It resists polar solvents, and not just water, but also acids, alkalies, and phosphate esters. EDPM does a great job of withstanding steam and low and high temperatures, though silicone can take on even higher temperatures.
The material has a low compression set, so it won’t lose much resilience over prolonged pressure.
You should also never use EPDM with oils, greases, hydrocarbon fuels, concentrated acids or halogenated solvents. Finally, EPDM has a shorter life span than Silicone, so depending on the application, it will need replacing more often.
Silicone is food safe. It’s an incredibly versatile material, thanks to its chemistry and the many ways that it can be modified. Consequently, it offers vast possibilities.
Perhaps its most appealing characteristic is its ability to take on extremely high temperatures, which is why it’s especially popular for masking applications. Manufacturers will all give different melting points based on their experience and own criteria, but generally silicone can stand up to 232°C/ 450°F. Compare that to EPDM’s 148°C/300°F.
Like EDPM, Silicone has outstanding resistance to ozone and weathering. Most manufacturers list its water resistance as excellent, but its water swell resistance is generally poor. Silicone can be modified to stand up to water, as seen by such products as silicone sealants. Otherwise, it lacks EPDM’s strength in this area. The U.S. independent materials testing lab, Polymer Solutions, writes that silicone “doesn’t have good acid and Alkali resistance, meaning that if it rains the rubber would be damaged and rendered useless.”
On the plus side, Silicone is resistant to automotive brake fluids, while EPDM is not. Silicone also has excellent compression set, which is even lower than EPDM’s.
While Silicone has good tensile strength, its abrasion resistance is generally poor. Note – it can be formulated to improve its tear resistance, however. Also, avoid using if the material will come into contact with steam over 121°C/249°F, hydrocarbon fuels, alkalis and acids, trichloroethylene, and aromatic hydrocarbons.
-40˚C – 150˚C/ -40˚F – 302˚F
-55˚C – 250˚C / -67˚F – 4482˚F
Good compression set
Excellent compression set
Excellent weather resistance
Excellent weather resistance when modified
Approx. tensile strength 14 MPa
Approx. tensile strength 5 MPa
Good abrasion resistance
Poor abrasion resistance
Not compatible with:
Not compatible with:
Wherever water and abrasion resistance are the first priorities, but EPDM isn’t only for outdoor applications; its water resistance makes it an excellent seal for plumbing applications too. Here are the most popular applications for EPDM and how it’s used:
Supports thermal expansion and resists vibration
Grommets that isolate vibrations while providing an airtight dust and watertight sealEnclosures
Good resistance to polar solvent
Sealing gaskets are used on metal sheets, providing an extra seal while isolating vibrations and keeping enclosures free of dust and water
Open hole grommet that turn metal into smooth openings for cables to pass throughAutomotive
Bonds quickly with metal, offers a strong barrier against the weather, and reduces force of engine’s vibrations
Flexible top bubble gasket can be pressed by hand or automation.
Dual-hard self-adhesive gaskets for areas that need to stand up to daily rigorous demandsMasking
Resistant to chemicals
Tight seal of Easy pull masking caps prevents paint ingress. Quick to apply and removeConstruction
Water and abrasion resistant
Single flipper gaskets create a weather seal around vents, doors and other openings. Flexible profiles can be applied by hand
Used as a roofing membrane, especially for low-sloped buildings, most commonly in U.S.Consumer Appliances
Protects against vibrations
Silicone properties include elongation, good thermal conductivity, and high resistance to very high temperatures make it a versatile material. Here are just some of the applications where it’s often used.
Excellent compression set
Fan mounts with high elongation provide excellent shock and vibration protectionMasking
Resistant to extremely high temperatures, which allows for blasting, powder coating, e-coating, anodizing, plating and wet painting
High-temperature plugs provide excellent sealing for plating, anodizing, spray painting and other finishing applications
Masking pull plugs for threaded and plain through-holes – material is flexible enough to allow for variation in sizes that need masking
Versatile masking straight caps fit over studs, pins or tube ends. Plugs mask threaded and non-threaded holes. Range of colors possible for easy identificationElectronics
Excellent stability against mechanical and electrical shock and vibration
USB and RJ Plugs protect entry from dirt and moisture ingressIndustrial
Flame retardant, flexibility and protects from radiation
Fire protection sleeves are self-extinguishing
Mouse tails plug very small holes with tight, sealed fit
Rotary dampers include silicone among other materials to provide damping resistanceCable Management
Outstanding thermal range and elongation
Cable straps can be stretched and wrapped around bundles
EPDM and Silicone aren’t your only choices, of course. Here’s a look at how they perform versus other rubbers:
Natural Rubber: Natural rubber is the strongest of all elastomers. It has an extremely low compression set, high tensile strength, fantastic elongation, and a high resistance to abrasions. EDPM and Silicone is no match for natural rubber in those categories. Where EPDM and Silicone tops natural rubber is its resistance to UV rays and ozone, which happens to be natural rubber’s weakness.
Silicone also beats natural rubber in heat resistance, which, depending on your application, might be another glitch in natural rubber’s properties.
Styrene-Butadiene rubber (SBR): SBR costs a lot less than Silicone and it has much better abrasion resistance than either Silicone or EPDM. Both silicone and EPDM have a lower compression set, however. EPDM beats SBR in tensile strength and resistance to heat aging and weathering.
Nitrile butadiene rubber (NBR): Nitrile is king of elastomers when it comes to oil- and fuel-resistance. One attraction to NBR is its stability in low temperatures, with the ability to survive extreme cold of -30˚C/ -22˚F, which EPDM and Silicone can’t match. On the other hand, both Silicone and EPDM stand up to higher temperatures, with Silicone topping EPDM. NBR is also more resistant to water swell and weathering elements.
Neoprene: This is an all-purpose elastomer. In compression set, neoprene is right there with EPDM, though neither match Silicone in that area. Neoprene matches EPDM stride for stride in properties such as compression set, resilience, and even ozone resistance. The two materials are,in fact, similar in a lot of ways. EPDM, however, has the edge in water swell resistance and a larger operable temperature range. Likewise, silicone has better resistance to water swimming and can withstand much higher temperature ranges.
Free CADs are available for most solutions, which you can download for free. You can also request free samples to ensure the solutions you’ve chosen are exactly what you need. If you’re not quite sure which product will work best for your application, our experts are always happy to advise you.
Request your free samples or download free CADs now.