EPDM vs Silicone Cold Shrink Tubing
“Is it EPDM or Silicone Cold Shrink?” That should be the question you’re asking before you purchase Cold Shrink tubing to weatherproof your coaxial connections. EPDM and Silicone are both fantastic weatherproofing options, but they do provide some different results in different circumstances. So which should you use?
Below we dive into the differences between EPDM and Silicone, and more specifically which works better for cold shrink tubing, to help you figure out which material better suits your needs.
EPDM vs. Silicone
EPDM stands for Ethylene Propylene Diene Monomer and is a synthetic rubber that is commonly used in roofing, as well as weatherproofing for doors and windows. It is sometimes also used to make gaskets for electronic applications. EPDM has great weather resistance and withstands Ozone and UV while also being resistant to temperatures ranging from -40° up to 130° Celsius, (or -40° to 266° Fahrenheit).
Silicone is a polymer made up of several different materials and is commonly used to make tubing, seals, and gaskets for a number of industries and applications. Like EPDM, Silicone has great weather resistance and withstands Ozone and UV, but Silicone has the added benefit of being able to withstand a far greater temperature range. Silicone will go down to -60° Celsius, (-76° Fahrenheit) before becoming brittle, and up to 230° Celsius, (446° Fahrenheit) before degrading.
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Furthermore, in their article “What is the Difference Between Silicone Rubber and EPDM?”, Silicone Engineering Ltd. illustrate that EPDM gradually shrinks as the temperature increases and sees severe deformity at about 125° C, (257° F). Silicone on the other hand, showed no change when exposed to the same temperatures.
EPDM does have the advantage however as being “seen as the more durable rubber compared to silicone”, (again citing Silicone Engineering). “However,” (they continue), “silicone is more flexible and can be formulated to have very strong tear resistance and elongation.” On top of being more flexible, Silicone is also more resistant to oil.
Which is Better for Cold Shrink Tubing: EPDM or Silicone?
In terms of what makes for better coaxial connector weatherproofing, silicone cold shrink tubing holds a major advantage over EPDM: shrink ratio.
Shrink ratio, in truth, is just a fancy way of saying the size of something before and after. For example, a 2:1 shrink ratio, (said “2 to 1”), means that a product starts 2 sizes larger than what it shrinks down to. Heat shrink is a product where we discuss shrink ratio all the time as it starts off one size and, once heat is applied to it, shrinks down to another. The same is true of cold shrink, it starts off as one size, and shrinks down to another, only it does not require heat to shrink.
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Our silicone cold shrink starts at 3.5 to 1, (3.5:1,), and peaks at about 4.5 to 1, (4.5:1). EPDM on the other hand usually has a shrink ratio around 2:1, peaking at a shrink ratio around 2.5:1. In other words, our silicone cold shrink doubles the shrink ratio of EPDM cold shink. This is a significant difference, especially when looking at these materials for use as cold shrink tubing for coax weatherproofing where shrinking down small and watertight is crucial.
You can see the difference between EPDM and silicone cold shrink tubing ratios in the animation below.
The higher shrink ratio of Gamma Silicone Cold Shrink allows it to shrink down smaller and tighter than EPDM ever could. In fact, many EPDM models of cold shrink are sold with a piece of foam meant to be placed between the cold shrink and the connector/cable the cold shrink is being installed on. The foam is only being utilized because the EPDM is not able to shrink down small enough to grab the cable on its own. The hope is the foam strip bulks up the cable/connection enough to create a watertight seal between the cold shrink and the foam strip. Far too often, EPDM fails to create that watertight seal: it just doesn’t shrink down small or tight enough.
In contrast, Gamma’s Silicone Cold Shrink can easily shrink down without the need for any foam strips. The shrink ratios that come with our silicone cold shrink allows for smaller models of cold shrink as well as larger models that create a better, more watertight seal.
You can see the difference between EPDM and silicone cold shrink tubing below, where we used toothpaste to demonstrate how much stronger the shrink ratio is with our silicone cold shrink tubing.
Let’s use our SDL-1A-125 Silicone Cold Shrink, which was made specifically for a larger than usual, 7/16 DIN connector, as an example. Because of its incredible shrink ratio, the SDL-1A-125 is able to shrink around not only the 7/16 DIN connector, but also the cable feeding into the connector, providing a complete weather seal, (as can be seen in the video). This type of shrink ratio and seal is pretty much impossible to accomplish with EPDM cold shrink.
Too often we have found that installers and/or contractors purchase EPDM Cold Shrink for use on RF connections not realizing that what they really want is Silicone Cold Shrink. Silicone Cold Shrink is more resistant to UV, Ozone, and Temperature while also having a far superior shrink ratio. In other words, Silicone Cold Shrink has all the attributes you want in your RF coaxial connector/cable weatherproofing.
“Too often we have found that installers and/or contractors purchase EPDM Cold Shrink for use on RF connections not realizing that what they really want is Silicone Cold Shrink.”
When Should I Use EPDM?
EPDM may not have the shrink ratio or weather resistant properties of silicone cold shrink, but there are still applications it is better suited than silicone cold shrink. For example, EPDM is very resistant to petroluem and often finds use around fuels.
EPDM is also more resistant to abrasion and/or friction. Silicone is quite strong, especially in comparison to heat shrink, but EPDM is more resistant to direct contact. Silicone works great high up on a tower where it will largely go untouched but EPDM is better suited for installation inside a machine where abrasion or friction is more likely.
Conclusion
If you’re using cold shrink tubing as weather protection for a coaxial connection you should make sure it’s silicone cold shrink, which provides greater weather/temperature resistance as well as superior shrink ratios. If you want to use cold shrink in or around machinery where abrasion is a factor you’ll want to go with EPDM cold shrink.
Gamma Electronics offers both types of cold shrink and our SDL (or silicone) models of cold shrink are an AT&T approved product being used on AT&T’s FirstNet buildouts.
