What Are EMI/RFI-Shielded O-Rings and Gaskets?

Global O-Ring and Seal supplies o-rings and gaskets that provide shielding against EMI (Electromagnetic Interference) and RFI (Radio Frequency Interference). EMI/RFI o-ring and gasket materials are filled with electrically-conductive particles used to reduce the effect of electronic interference from electronics and electro-mechanical devices. Our EMI o-rings and gaskets compare closely to Parker Chomerics EMI o-rings and gaskets.

Electrically conductive o-rings and gaskets with EMI shielding are applied to enclosure covers, doors, and vulnerable areas to prevent or restrict electromagnetic emission from interfering with other electronic components. As electronic devices play an ever-larger role in automotive, aviation, medical, other industries, the electromagnetic/radio frequency interference (EMI/RFI) shielding market continues to grow.

In addition to managing EMI and RFI interference, electrically conductive o-rings and gaskets are used for environmental sealing. EMI o-rings and gaskets can be designed to be:

  • Weather-Resistant to seal out rain and sleet (IP54, NEMA 3)
  • Watertight to withstand pressure washing (IP65, IP66, NEMA 4X)
  • Submersible to prohibit ingress underwater (IP67, NEMA 6)

If you would like more information, or to request a quote, please give us a call at 832-408-9975 or fill out the Product Inquiry form to confirm your request is being met.

EMI/RFI O-Ring and Gasket Compounds

The EMI/RFI materials typically use a base of either silicone or fluorosilicone, which is then filled with metal or metal-coated particles. Silicone material can withstand water, ozone, UV light, and a wide range of temperatures. Fluorosilicone material has all of the features of Silicone with added resistance to fuels and solvents. The metal or metal-coated particles include silver-aluminum, silver-copper, nickel-aluminum, and nickel-graphite particles. These fillers differ in terms of cost, conductivity, and typical volume resistivity (VR) – an indirect measure of shielding effectiveness.

Silicone o-rings and gaskets filled with nickel-graphite are widely used for commercial applications where the higher cost of silver-based filler materials is prohibitive. Aerospace and Defense applications often require materials that meet MIL-DTL-83528 which most often include silver-based fillers.

The table below provides a high-level summary of EMI materials, along with their equivalent Parker Chomerics EMI compounds.

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Compound Name
Compound Composition
MIN Shielding Effectiveness 20 MHZ to 10 GHZ (MIL-DTL-83528)
Parker Chomerics Compound Interchange
EMI-2368 Silver Aluminum in Silicone $$$$ 65 .008 ohm/cm 100 dB Meets MIL-DTL-83528, TYPE B 1285
EMI-550, EMI-2486 Silver Aluminum in Fluorosilicone $$$$ 70 .012 ohm/cm 100 dB Meets MIL-DTL-83528, TYPE D Fuel and Solvent Resistant 1287, 1298
EMI-547, EMI-553 Silver Copper in Silicone $$$$ 65 / 80 .004 ohm/cm 110 dB Highest Conductivity and Shielding Available 1215
EMI-2529 Nickel Aluminum in Silicone $$$ 70 .15 ohm/cm 100 dB Corrosive Resistant 6502
EMI-2551 Nickel Aluminum in Fluorosilicone $$$ 70 .25 ohm/cm 100 dB Corrosive Resistant, Fuel and Solvent Resistant 6503
EMI-502F Nickel Graphite in Fluorosilicone $$ 60 .1 ohm/cm 100 dB Fuel and Solvent Resistance L6303
EMI-502 Nickel Graphite in Silicone $ 65 .1 ohm/cm 100 dB Lowest Cost with High Shielding 6308

EMI/RFI Profiles and Vulcanization

O-rings and gaskets are vulcanized from any of the profiles shown below with a bonding agent that ensures continuity of the EMI/RFI protection at the joint. This is critical to achieving the overall results. The overall conductivity and EMI suppression of a vulcanized EMI/RFI o-ring are equivalent to a molded EMI/RFI o-ring but at a much lower price. Read more on how vulcanized EMI/RFI o-rings are the better economical option. Below, is a table showing the most common extrusion profiles we have readily available.

Profile Profile Image Description Profile Profile Image Description
SO Solid O-Shape HO Hollow O-Shape
HOSB Hollow O-Shape

w/ Symmetrical Base

HOAB Hollow O-Shape

w/ Asymmetrical Base

SD Solid D-Shape HD Hollow D-Shape
SR Solid Rectangular Shape RC Rectangular Channel Shape


EMI O-Ring and Gasket Part Numbering

Part numbering for EMI o-ring and gaskets uses the following format: EMI, Material Code, Profile Code, Dimension A (Inches), Dimension B (Inches), Dimension C (Inches), and Dimension D (Inches). If a profile does not have four dimensions, only the existing values apply. The example below shows an EMI o-ring made with Nickel Graphite in Fluorosilicone material and a Rectangular Channel Shape profile.

If you have any questions or would like a quote on EMI/RFI products or if your application specifically requires Parker Chomerics, please give us a call at 832-4448-5550 or fill out the Product Inquiry form. We will respond to your request within one business day.