Conductive silicone is silicone rubber filled with conductive particles — carbon, nickel-coated graphite, or silver-based fillers.
It seals an enclosure against dust and water AND blocks electromagnetic interference (EMI) at the same time.
It is the standard material for EMI shielding gaskets in electronics, telecom, and military equipment.
What Is Conductive Silicone?
Standard silicone rubber is an electrical insulator. Conductive silicone changes that by mixing conductive filler particles into the rubber compound.
The particles touch each other inside the rubber and form a conductive network. The finished part keeps silicone’s flexibility and sealing ability — but now it also conducts electricity.
This dual function is exactly what an EMI shielding gasket needs:
Filler Types: The Heart of the Material
The filler determines conductivity, shielding performance, and cost:
Filler | Volume Resistivity | Shielding Level | Cost | Typical Use |
|---|---|---|---|---|
Carbon black | 5–50 Ω·cm | Low (anti-static) | Low | Static discharge, not true EMI |
Nickel-coated graphite (Ni/C) | 0.01–0.1 Ω·cm | Good | Medium | Commercial electronics, telecom |
Silver-coated aluminum (Ag/Al) | 0.002–0.01 Ω·cm | High | High | Military, aerospace |
Silver-coated copper (Ag/Cu) | 0.002–0.008 Ω·cm | High | High | High-performance EMI |
Pure silver | <0.002 Ω·cm | Highest | Very high | Critical military/aerospace |
Tips from ZSR: Nickel-coated graphite covers most commercial EMI needs at a reasonable cost. Silver fillers are for military specs and demanding shielding levels. Do not over-specify — tell us your shielding target (dB) and frequency range, and we match the filler to it.
Key Properties
Property | Typical Value |
|---|---|
Temperature range | -55°C to +160~200°C (filler dependent) |
Hardness | Shore A 50 to 80 |
Volume resistivity | 0.002 to 10 Ω·cm (by filler) |
Shielding effectiveness | up to 90–110 dB (high-grade fillers) |
Weather / ozone resistance | Excellent |
Compression set | Good |
Where Conductive Silicone Is Used
Forms We Supply
Conductive silicone is not only O-rings:
Conductive Silicone vs Other EMI Solutions
Solution | Seal + Shield in One? | Notes |
|---|---|---|
Conductive silicone gasket | Yes | Best all-round: sealing, shielding, weatherproof |
Metal finger stock | Shield only | No environmental seal; needs separate gasket |
Conductive fabric over foam | Partial | Soft and cheap, but poor weather sealing |
Wire mesh gasket | Shield only | Rugged but no dust/water seal |
What to Specify When Ordering
To quote a conductive silicone gasket, we need:
Advice from ZSR: Galvanic corrosion matters. Silver-filled gaskets against aluminum enclosures in humid, salty air can corrode the housing. For marine or outdoor use, nickel-graphite or silver-aluminum fillers matched to the housing material are safer. Tell us the enclosure material — we check the pairing.
MIL-DTL-83528 Material Types Explained
MIL-DTL-83528 (formerly MIL-G-83528) is the US military specification for electrically conductive elastomer EMI shielding gaskets. It defines material types by base polymer, conductive filler and performance. If a defense or aerospace drawing calls out a type, this table shows what it means.
| Type | Base Polymer | Conductive Filler | Temp Range | Shielding Effectiveness | Hardness |
|---|---|---|---|---|---|
| A | Silicone | Silver-coated copper | -55°C to 125°C | 110 dB @ 10 GHz | 65–75 Shore A |
| B | Silicone | Silver-coated aluminum | -55°C to 160°C | 100 dB @ 10 GHz | 65–75 Shore A |
| D | Fluorosilicone | Silver-coated aluminum | -55°C to 160°C | 90 dB @ 10 GHz | 65–75 Shore A |
| E | Silicone | Pure silver | -45°C to 125°C | 110 dB @ 10 GHz | 65–75 Shore A |
| K | Silicone | Silver-coated copper | -55°C to 125°C | 110 dB @ 10 GHz | 85 Shore A |
| L | Silicone | Silver-coated nickel | -55°C to 125°C | 100 dB @ 10 GHz | 65–75 Shore A |
| M | Silicone | Silver-coated glass | -55°C to 160°C | 100 dB @ 10 GHz | 65–75 Shore A |
| Type | Corrosion Resistance | Galvanic Compatibility | Relative Cost | Best Suited For |
|---|---|---|---|---|
| A | Good | Best with copper alloys | Moderate | General-purpose shielding with copper housings |
| B | Excellent | Good with aluminum alloys | Moderate | Aerospace enclosures, aluminum housings |
| D | Excellent | Good with aluminum alloys | High | Fuel / oil / solvent exposure |
| E | Superior | Compatible with most metals | Very high | Maximum shielding effectiveness |
| K | Good | Best with copper alloys | Moderate | High-compression, firm gasket applications |
| L | Excellent | Compatible with most metals | Moderate–high | Where corrosion resistance is critical |
| M | Excellent | Compatible with most metals | High | High-temperature applications |
Values are typical published figures for the specification, shown for orientation. Every ZSR compound batch is verified against its datasheet — ask for the test report with your quote. Not sure which type fits? Send us the drawing and the housing material; we will recommend a filler and confirm it with samples. See ZSR certifications.
Shielding Effectiveness: What the dB Numbers Mean
Shielding effectiveness is measured in decibels (dB) across a frequency range. Every 20 dB means the transmitted field strength drops by a factor of 10 — 100 dB means only one ten-billionth of the incident energy gets through.
| Filler System | Volume Resistivity | Typical Shielding (100 MHz – 1 GHz) | Typical Shielding (1 – 10 GHz) |
|---|---|---|---|
| Carbon black | 5–50 Ω·cm | < 20 dB (not true EMI) | < 20 dB |
| Nickel-coated graphite | 0.01–0.1 Ω·cm | 60–90 dB | 80–100 dB |
| Silver-coated aluminum | 0.002–0.01 Ω·cm | 80–100 dB | 90–110 dB |
| Silver-coated copper / pure silver | < 0.002–0.008 Ω·cm | 90–110 dB | 100–110+ dB |
Actual performance depends on part geometry, flange design and compression. We test shielding to IEEE 299 / MIL-DTL-83528 methods on request — tell us your target frequency range and required dB level when requesting a quote.
How to Choose the Right Conductive Filler
Six questions that decide the filler — answer them and the material usually picks itself.
1. Frequency & Target dB
Match the filler to your emission profile. Commercial electronics usually need 60–90 dB (nickel-graphite); military and aerospace specs above 100 dB point to silver systems.
2. Gap & Compression
Conductive silicone needs consistent flange pressure to keep the conductive network closed. Larger gaps or uneven flanges may call for FOF or foam instead — see the comparison below.
3. Housing Material & Galvanics
Silver fillers against aluminum in humid or salty air risk galvanic corrosion. Match filler to housing (silver-aluminum for aluminum enclosures, nickel-graphite as a safe general choice).
4. Environment
Outdoor exposure, salt spray and fuel splash change the answer. Fluorosilicone-based conductive compounds (MIL Type D style) handle fuels and oils; platinum curing keeps properties at 150°C+.
5. Cost Gradient
Carbon < nickel-graphite < silver-aluminum < silver-copper < pure silver. Do not over-specify — a nickel-graphite gasket that passes your test is a better buy than a silver one.
6. Seal + Shield in One?
If the part must also seal against dust and water, conductive silicone or fluorosilicone is the natural choice — pure shielding materials (finger stock, mesh) leave the environmental gap open.
Conductive Silicone vs Other EMI Shielding Materials
Conductive silicone is one of five common EMI gasket families. Each solves a different gap, compression or frequency problem.
| Material Family | Construction | Seal + Shield? | Best For | Watch Out For |
|---|---|---|---|---|
| Conductive silicone (filled elastomer) | Silicone / fluorosilicone with metal particle fillers | Yes | Outdoor enclosures, wide temperature, MIL-SPEC parts, molded custom shapes | Higher cost than foam; needs flange compression |
| Conductive foam | Metal-plated open-cell PU foam | No | Low compression force, wide gaps, reworkable assembly | Poor environmental seal; degrades over time |
| Fabric-over-foam (FOF) | Conductive fabric wrapped over foam core | No | Very wide gaps, display and chassis shielding at low force | Not weatherproof; edge fraying in die-cutting |
| Conductive adhesive tapes | Foil / fabric / filled PSA, Z-axis or XYZ | No | PCB grounding, shield-can attachment, bond-line shielding | Flat surfaces only; not a gasket material |
| EMI absorbers | Magnetic-particle composite sheet | No | Absorbing noise at the source (100 MHz – 6 GHz) | Converts energy to heat; does not seal or ground |
ZSR supplies conductive silicone as compression-molded gaskets, extruded profiles and sheet for die-cut parts — one material family, three production routes, all in-house.
Testing & Standards Behind the Numbers
Shielding claims are only as good as the test method behind them. These are the standards buyers ask about most.
| Standard | What It Covers | How ZSR Uses It |
|---|---|---|
| MIL-DTL-83528 | Conductive elastomer gasket materials: types, fillers, shielding and hardness requirements | Compounds formulated to type; batch test reports available |
| IEEE 299 | Standard method for measuring shielding effectiveness of enclosures | Shielding validation on assembled parts on request |
| ASTM D4935 | Planar shielding effectiveness of materials over 30 MHz – 1.5 GHz | Material-level screening of new compounds |
| ASTM D991 | Volume resistivity of conductive rubber | Every production batch |
FAQs
Need an EMI Shielding Gasket?
ZSR molds conductive silicone gaskets, O-rings, and extrusions in-house. Tell us your shielding target and enclosure material — we will recommend the right filler and design.
Send your drawing or requirements. Answer within 24 hours.
Related reading: Silicone Rubber Material Guide | What Is VMQ Silicone Rubber? | HTV vs LSR Silicone