Synthetic polymers come in different types. And it’s not uncommon to confuse one kind of polymer over another. For instance, we often find people mistaking silicone rubber with EPDM and vice versa.
Both of these materials are identical in a variety of ways. And both possess many desirable properties that make them ideal for countless industrial uses.
So what’s the difference between silicone rubber and EPDM? Which one should you choose for your particular application? Stick around because, in this article, we’re going to answer all these questions and more.
First, let’s get down to the basics and define silicone rubber and EPDM.
1. What is Silicone Rubber?
Silicone rubber is a high-performance synthetic elastomer. As the name suggests, this elastomer is made of silicone – chemicals with a siloxane backbone. You can formulate them as either one-part or two-part polymeric materials. And curing them is via either peroxide or platinum agent.
There are many ways to process silicone. And the processing method you go for depends on which properties you want to see in your end product. You can also apply fillers to manipulate resulting properties and manufacturing costs.
Silicone rubbers see extensive use in diverse industries because of their many valuable qualities. Below are some of the most notable ones:
- Extreme temperature resistance (maintains exceptional performance within -60°C – 200°C)
- Weatherability (excellent resistance to oxygen, ozone, and UV rays)
- High chemical inertness (does not react to solvents, oils, and other chemicals)
- Electrical insulation (1TΩ·m –100TΩ·m) and conductivity (0.01Ω·m to 10Ω·m)
- Thermal conductivity (0.2 W/mΩ.K)
- Long service life
- Non-toxicity (can be used for food and medical applications)
- It has an inferior tear strength compared to EPDM rubber.
- Silicone rubber costs higher than other polymers, including EPDM
2. What is EPDM Rubber?
EPDM (Ethylene Propylene Diene Monomer) rubber is another popular type of synthetic polymer. It consists of the chemical compounds stated in its name. These chemicals make up its single bond, polymethylene backbone.
Like silicone, you can process EPDM in various ways, depending on your desired characteristics. Curing is done using either sulfur or peroxide agents. You can also compound EPDM with fillers to influence end characteristics.
EPDM, like silicone rubber, is widely used in various industries and applications. This extensive usage stems from its many valuable characteristics. Some of which are:
- Weatherability (resist abrasion, UV rays, ozone, aging, and weather)
- Chemical inertness (resists a wide range of chemicals)
- Excellent flexibility and tensile capacity (500 – 2500 psi)
- Superior tear strength compared to silicone rubber
- Great noise insulating properties (ideal for aviation and automotive applications)
- Non-toxicity (can be used for food and medical applications)
- Lower in cost compared to silicone rubber
- Inferior temperature resistance (-45°C – 130°C)
- Shorter service life compared to silicone rubber
3. Silicone and EPDM: Head-to-Head Comparison
To understand the differences (as well as similarities) between these two materials, let’s look at how they compare in terms of essential factors. Think of these factors as “must-haves” for a high-quality synthetic polymer.
3.1 Performance at Extreme Temperatures
Operating temperatures can directly impact a material’s performance and service life. Extreme temperatures can damage a non-durable rubber, causing melting and permanent deformations.
In terms of temperature resistance, silicone is superior compared to EPDM.
EPDM can only operate within a -45°C – 130°C temperature range. Silicone, on the hand, offer more flexibility. It can perform under temperatures as low as -60°C and withstand as high as 200°C without failure.
3.2 Environmental Resistance
Synthetic rubbers are no stranger to outdoor applications. In these applications, the rubber is constantly exposed to harsh environmental elements. These include extreme weather, ozone, and the sun’s UV rays. Exposure to these natural elements can speed up a rubber’s wear and tear.
Both silicone and EPDM rubbers possess exceptional environmental resistance. This makes them both ideal for outdoor applications.
3.3 Tensile Strength
Assessing a rubber’s tear strength is vital, especially when placed under prolonged heavy-duty applications. EPDM is superior when it comes to withstanding the effects of tearing. You can reach this same level of tear resistance with silicone rubber. But you’ll have to use a unique formulation.
3.4 Health and Environmental Safety
You can consider both silicone and EPDM rubbers to be safe and eco-friendly. These polymers don’t contain the harmful chemicals you’ll find in plastics and other rubbers.
You can even manufacture these two synthetic polymers to meet food-grade and medical-grade requirements, such as those from the ISO, USP, and FDA.
3.5 Industry Applications
Both silicone and EPDM have many industrial uses. But the main difference is that silicone rubbers are used more extensively in general applications. EPDM, on the other hand, see more specific use-cases, especially in the fields of HVAC and automotive.
Regardless, you can apply both rubbers for similar functions, including those requiring contact with food and human skin. For many of these applications, It’s only a matter of preference.
3.6 Material Cost
Silicone tends to be more expensive than EPDM. But it generally has a longer service life. This gives you better long-term cost savings since you won’t have to replace parts often when employing silicone rubber. You can also steer clear of prolonged downtime disruptions caused by parts breaking down early.
4. Choosing the Right Material for Your Application
Both synthetic rubbers have their own advantages and drawbacks. But they do share a lot of similar qualities. For instance, both materials have excellent environmental resistance and electrical properties. Both also possess good chemical inertness and are made up of non-toxic components.
Basic Comparison of Silicone Rubber and EPDM Rubber
In terms of differences, silicone rubber has better temperature resistance and can last longer. On the other hand, EPDM has better tensile strength and is much friendlier to your wallet short term. It’s best to keep these in mind when choosing which material to source for your application.
Another vital thing to mention is that while EPDM costs lower, it’s inferior to silicone rubber regarding lifespan. If you’re after cost savings, opting for the more mainstream-use silicone rubber is better in the long run.