Low Outgassing Silicones for EMI Shielding
Low outgassing silicones for EMI shielding meet ASTM E 595 requirements for outgas testing and help protect electrical equipment and electronics against electromagnetic interference (EMI). Outgassing, the release of a gas trapped in a solid material, is a problem in high-vacuum environments like outer space because released gases can condense upon and cloud optics. EMI can disturb or disrupt the electronic circuits used in spacecraft, satellites, and high-altitude aircraft.
Specialty Silicone Products (SSP), a leading manufacturer of low outgassing silicones for EMI shielding, supplies four EMI elastomers that use optimized formulations to limit outgassing and that have been independently testing according to ASTM E 595. These four EMI elastomers use silicone or fluorosilicone as the base material and are packed with metal-coated particles. Some meet U.S. military specifications for EMI shielding.
SSP-2368-65 is a 65-durometer shielding silicone that’s filled with silver-aluminum particles, meets MIL-DTL-83529 Type B requirements, and is part of the U.S. Department of Defense (DoD) Qualified Products List (QPL). This EMI elastomer is recommended for military satellite and missile defense applications that require low outgassing and reliable shielding. The MIL-DTL-83529 standard is a trusted specification. A third-party shielding report for SSP-2368-65 is available.
SSP-2486-70 is a 70-durometer EMI material that uses fluorosilicone as the base material and is filled with silver-aluminum particles. This elastomer meets MIL-DTL-82528 Type D shielding requirements. Because SSP-2486-70 uses fluorosilicone instead of silicone, it’s suitable for environments where there’s exposure to fuels and solvents. Military and aerospace applications include EMI gaskets where there’s contact with jet fuel or de-icing fluids. A third-party shielding report for SSP-2486-70 is available.
SSP-2476-65 provides the highest electrical conductivity in an EMI material that meets ASTM E 595 low outgassing requirements. This 65-durometer EMI elastomer isn’t on the QPL nor does it meet the lettered standards in MIL-DTL-82528; however, SSP-2476-65 is firmer than some other EMI elastomers, which makes it good choice for a grounding material or O-rings.
SSP-2529 is a 68-durometer, nickel-aluminum EMI silicone that provides galvanic corrosion resistance and EMI shielding in marine environments with salt spray or fog. This EMI elastomer has been tested to MIL-83528F. A third-party shielding report is available. Nickel-filled materials are on lists of forbidden products because of their potential for skin irritation, but the low-outgassing properties of SSP-259 offer assurances that is a relatively clean material where the nickel is embedded in the elastomer.