Conductive silicone rubber is a special type of silicone material that can conduct electricity.
Normally, silicone is an electrical insulator, meaning that it doesn’t let electricity flow through it. When silicone is mixed with electrically conductive particles, however, the resulting compound becomes able to carry electrical current.
Applications for conductive silicone rubber include:
EMI/RFI Shielding
Seals and gaskets
Keypads
Sensors and wearable tech
Among its advantages, conductive silicone rubber is flexible, weather-resistant, and can withstqand a wide range of temperatures. Keep reading to learn more, and contact SSP for conductive silicone materials or products.
Material Properties
Electrically conductive silicone rubber is a composite material. Typically, the base is polydimethylsiloxane (PDMS). To this base, conductive fillers such as carbon black, silver-plated particles, nickel-coated graphite, or pure silver are added. The choice of filler determines the level of electrical conductivity, mechanical properties, and cost of the final product.
Electrical Characteristics
Conductive silicone rubber exhibits a wide range of resistivity, typically from 10³ to 10⁻³ ohm·cm depending on the filler concentration and type. The percolation threshold,the minimum amount of conductive filler required to create a conductive path, is critical. Beyond this threshold, conductivity increases significantly. Fine-tuning the filler concentration is essential to achieve the desired balance between electrical conductivity and mechanical flexibility.
Mechanical and Thermal Properties
Silicone rubber maintains excellent mechanical resilience even after the addition of conductive fillers. It remains highly flexible, with typical elongations at break exceeding 100%, and can operate across a wide temperature range, typically from -55°C to 200°C. Conductive silicone rubber also retains outstanding weatherability, UV resistance, and chemical inertness.
Manufacturing and Curing
The manufacturing of conductive silicone rubber typically begins with compounding, where the conductive filler is thoroughly mixed into the silicone base. This step must ensure a uniform dispersion of particles to maintain consistent electrical properties. Following compounding, traditional rubber manufacturing techniques are used to shape the material.
Quality Control
For critical applications—such as EMI gaskets for aerospace systems—stringent quality control during manufacturing is essential. Voids, agglomerations of filler, or incomplete curing can affect both electrical conductivity and mechanical integrity.
Curing Mechanisms
There are two main curing methods for conductive silicione rubber.
Addition-cure (platinum-catalyzed) systems offer vulcanization with minimal shrinkage.
Peroxide-cure systems are generally used for high-temperature applications but can leave byproducts that affect conductivity.
Engineering Applications
Conductive silicone rubber is used in these and other applications.
EMI/RFI Shielding
One of the main uses of conductive silicone rubber is in shielding against electromagnetic interference (EMI) and radio-frequency interference (RFI) shielding. In electronics, especially designs where dense circuitry is susceptible to noise, conductive silicone gaskets provide both environmental sealing and EMI shielding in enclosures.
Keypads and Switches
In consumer electronics and medical devices, conductive silicone is used in keypads and membrane switches. By incorporating conductive “pills” under buttons, manufacturers can create low-cost, highly reliable contact mechanisms. These switches typically have excellent tactile response, long service life (millions of actuations), and resistance to contaminants.
Flexible Sensors and Wearables
With the growth of wearable technology, conductive silicone rubber is increasingly used in flexible sensors. Strain gauges, touch sensors, and bioelectrical impedance devices all benefit silicone rubber’s flexibility and skin-safe properties. Engineers can design stretchable circuits that maintain their function under mechanical deformation, something that is difficult to achieve with rigid substrates.
Thermal Management
In some formulations, conductive silicone rubber can also provide thermal conductivity. When loaded with thermally conductive yet electrically insulating fillers (such as boron nitride), or thermally and electrically conductive fillers (such as silver), the material can serve as a thermal interface material (TIM) for dissipating heat from sensitive electronics.
Design Considerations
Design considerations include filler selection, compression set and aging, and environtmenal factors.
Filler Selection
Filler materials include:
- Silver-coated particles: high conductivity, higher cost, excellent EMI shielding.
- Nickel-coated graphite: good compromise between cost and performance.
Carbon black: inexpensive, moderate conductivity, good flexibility.
Filler morphology (particle size, shape, surface treatment) also significantly affects conductivity and mechanical properties.
Compression Set and Aging
Compression set is a material’s tendency to deform permanently under load, which can can affect gasket sealing over time. Consider aging under high temperature, ozone, or other harsh environments during material selection and life-cycle testing.
Environmental Factors
When specifying conductive silicone rubber for outdoor or biomedical use, ensure that the material meets the necessary certifications, such as UL94 for flammability or U.S. military standards standards like MIL-DTL-83528.
Cost Considerations
Highly conductive fillers such as silver significantly drive up the material cost. In many applications, engineers must optimize the balance between conductivity, mechanical performance, and economic feasibility. Hybrid fillers and coating
Future Trends
The future of conductive silicone rubber includes nanotechnology, advanced composites, and reinforcements. Incorporating carbon nanotubes, graphene, or silver nanowires could enhance electrical properties at lower filler loadings, preserving flexibility and reducing weight.
Furthermore, additive manufacturing (3D printing) techniques are being developed to allow direct printing of conductive silicone parts, opening new possibilities in prototyping and custom device manufacturing.
Smart materials—such as self-healing conductive silicones and stimuli-responsive composites—are also being researched. These materials could find applications in autonomous systems, soft robotics, and intelligent wearables.
Find Conductive Silicone Rubber
Conductive silicone rubber combines the mechanical versatility of silicone elastomers with the electrical properties of metals. Its applications are broad, ranging from EMI shielding in aerospace to flexible electronics in wearable devices. Contact SSP for ready-to-fabricate materials or ready-to-install products.
