Silicone Gaskets

Silicone Gasket Material – The Ends and Outs

What a difference an “e” makes! Silicon is the material of electronics. It’s hard and brittle and makes lousy gaskets. Silicone on the other hand is soft and elastic, which makes it a good choice in many gasket applications. Here’s what makes this polysiloxane material so useful.

Basic Chemistry

Silicon and silicone are closely related. Silicon is a naturally-occurring element while silicone is a polymer that combines silicon atoms with those of oxygen and the H3C hydrocarbon compound. The result is a soft, plastic-like material that springs back after being compressed.

More Silicone Properties

In addition to compressibility, other useful features of silicone include:

  • Poor adhesion, so it doesn’t mark surfaces
  • Low toxicity, making it useful for food and medical applications
  • Resists degradation by ultraviolet light (sunlight)
  • Low electrical conductivity
  • Repels water
  • Ozone resistant
  • Retains its flexibility over a temperature range of -94 to +392°F

These properties make silicone gaskets a good choice in a range of food, medical and electrical applications. It won’t taint foods and it handles a wider temperature range than many other gasket materials.

Silicone Weaknesses

In some regards, silicone performs less well as a gasket material than the alternatives. Some others have higher strength and better compression set recovery for instance. It’s also attacked by hydrocarbons like most oils and fuels, and resistance to acids and alkalines is poor. In short, unless you need the special properties of silicone there may be better alternatives.

Silicone Forms

Silicone is available in both solid sheet and as a foamed or cellular material. Silicone foam may be either closed or open cell.

Silicone comes in many colors, (which may not be food grade, so check before ordering.) There are also many variants tailored for specific application needs. Some will go to lower temperatures than that given above, while others have been engineered for higher strength or even electrical conductivity.

If you’re considering using silicone gaskets we respectfully suggest speaking with one of our material specialists. There are many instances where silicone is an excellent choice, but sometimes other materials may perform better.

Enclosure Sealing to Prevent EMI Leakage

The silicone gasket around the door or access panel of an electrical enclosure has two jobs. Not only does it keep dust out, but it also keeps electrical noise in. Or it does if made from the right material.

The Noise Problem

Electrical noise, sometimes called electromagnetic interference (EMI) or radio frequency interference (RFI) is a problem in some environments. By interfering with wireless transmissions EMI makes phone calls difficult and disrupts wireless data transmission. It can also induce currents in other conductive materials. That can lead to spurious data signals, possibly giving rise to false alarms or affecting process control equipment.

Conversely, sometimes sensitive electrical equipment needs shielding from environmental EMI. Placing it in a metal enclosure keeps the EMI outside, avoiding problems of signal interference.

EMI Sources

EMI travels through air, spreading out from a source much like ripples on a pond. Circuit breakers, relays, transformers and switches can all produce EMI. This is one reason they’re often placed in an enclosure. Motors, power cables and welding equipment also produce EMI, but aren’t so easily shielded. However, sensitive electronics near these items may need to go in an enclosure.

Conductive Shielding

When waves of EMI meet a conductive material the energy spreads out over the surface rather than continuing on. Gaskets and flanges however provide an opportunity for leakage.

With most enclosures, closing the door leaves an uneven gap. That could allow dust inside, which is the main reason a gasket is fitted around the opening. Electrical enclosures are usually sealed with silicone gaskets, which offer good compression and stand up to elevated temperatures. However, silicone is not naturally electrically conductive. That results in a leak path where EMI can escape.

Ask for Electrically-Conductive Gasket Material

When replacing gaskets around an electrical enclosure, or specifying new, always consider the need for EMI shielding. Electrically-conductive gasket materials are available, but it’s important this issue is raised when speaking with the material supplier. In many cases conventional silicone gasket material will be sufficient, but if EMI could be a concern, let your vendor know.

Properties of Neoprene Gasket Material

Neoprene, which is also known as “polychloroprene,” is a type of synthetic rubber produced by the polymerization of chloroprene. Neoprene gasket material has become very common due to the fact that it resists the likes of ozone, sunlight, oxidation and many petroleum derivatives. Additionally, neoprene is characterized as being weather-, combustion-, water- and chemical-resistant. As you can see, it’s popular because it is resistant to many types of damages. What’s more, it’s also resistant to damage from twisting and flexing.

Here’s a closer look at the properties of neoprene so you can judge whether or not it’s a good material for your application:

  • Stretch and cushioning properties: Neoprene is elastic and form-fitting, able to conform to various sizes and shapes. It’s also cushioning, able to absorb shock.
  • Various grades available: From cloth inserted neoprene, which is reinforced with nylon for additional stability, to flame retardant neoprene, which passes a variety of flammability specifications, there are several grades available to suit any application. Other popular grades include commercial, FDA approved, diaphragm and high tensile strength.
  • General gauge thicknesses vary in size from 3/32-inch up to 2 inches.
  • Hardness ratings vary from 40 to 80.
  • Plate finish.
  • Neoprene can withstand temperatures ranging from -20 degrees F to 180 degrees F.
  • Tensile strength ranges from 900 to 1,000 PSI.
  • Elongation ranges from 350% to 400%.
  • Finally, widths are 36 inches, 48 inches or 72 inches.
  • Pressure sensitive adhesive, or PSA, are available upon request.
  • We fabricate neoprene gaskets through proven manufacturing processes that include waterjet cutting, flash cutting and die cutting.

One other neat feature about neoprene is that it’s impermeable, meaning that it can work as a tight barrier to prevent the escaping of gases or liquids.

For more information on the neoprene material and neoprene gaskets, and to speak with someone about placing an order, contact us today.