Does Silicone Conduct Electricity?

Silicone is a synthetic polymer based on silicon and oxygen. Organic groups and other components allow it to be adapted flexibly to different requirements, making it a versatile material for numerous applications. Depending on its composition, different types of silicone vary in their properties and possible uses.

Thanks to its special properties, silicone is used across numerous industries. It is used, among other things, for seals in the automotive industry, for medical or household products, and for many other technical and industrial components. In medical technology, for example, silicone is used wherever materials must meet demanding requirements for durability, flexibility and safety.

Depending on the application, this results in a range of silicone rubber solutions for industrial, medical and technical uses. Its versatility makes silicone one of the most important materials in modern manufacturing processes.

Further reading: Learn more about its special properties and applications in our article on medical silicone.

Is Silicone Electrically Conductive or an Insulator?

In its natural state, silicone is not electrically conductive; it is an electrical insulator. Its electrical behaviour therefore differs significantly from that of metals and semiconductors. However, adding conductive fillers can selectively increase the electrical conductivity of silicone.

The following properties are primarily responsible for this:

• High electrical resistance: The chemical structure of silicone results in very low electrical conductivity and restricts charge transport. Pure silicone typically has a volume resistivity above 10¹⁴ Ω·cm.
• Temperature resistance: Silicone retains its insulating properties across a wide temperature range, making it suitable for a variety of operating conditions.
• Moisture resistance: Silicone absorbs very little moisture and therefore remains largely insulating even in humid conditions. This also helps protect sensitive electronic components from moisture and dust.
• Chemical resistance: Many chemicals have little effect on silicone, allowing it to retain its material properties even under demanding operating conditions.
• Durability: Silicone is resistant and retains its material properties under many demanding environmental conditions.

Conductive silicone is used in electronics, sensor technology, electromobility and telecommunications, among other fields. Other applications include EMI shielding, electrical contacts and medical electrodes. In EMI shielding, the conductive network in the silicone does not primarily transport current; instead, it reflects and attenuates electromagnetic waves to protect sensitive components from interference.

Depending on the application, the material must meet different requirements and safety standards. The necessary certification depends on the field of use, the specific application and the applicable standards.

How Is Silicone Made Electrically Conductive?

Without special additives, silicone acts as an electrical non-conductor. Only by incorporating conductive fillers and additives does the material become able to conduct electric current. Conductive silicone has antistatic properties. It can be used, for example, to reduce the accumulation of electrostatic charge.

The incorporated particles form conductive connections within the silicone matrix through which electric current can flow. Silicone conductivity is achieved through the principle of percolation: once a certain concentration is reached, the conductive fillers form a continuous network within the silicone matrix.

Depending on the desired conductivity and application, different materials are used.

Conductive Fillers

Conductive fillers create electrical conduction paths within the silicone.

• Carbon black: A cost-effective carbon filler used to improve electrical conductivity.
• Graphite: Increases conductivity and can also improve the mechanical properties of silicone.
• Carbon nanotubes (CNTs): Offer very high electrical conductivity as well as improved thermal stability and strength.
• Graphene: Improves electrical performance and is suitable for demanding applications.
• Silver particles: Silver is one of the most electrically conductive metals and enables particularly high conductivity.
• Copper particles: Provide a more economical alternative to silver while still offering good electrical conductivity.

Functional Additives

In addition to conventional fillers, other additives can influence electrical properties.

• Ionic liquids: Support ionic conductivity and are used in specialised conductive silicone applications.
• Conductive polymers: Materials such as polyaniline or polypyrrole are combined with silicone to extend its electrical properties.

Adhesion Promoters and Surface Treatments

These additives do not directly improve conductivity, but they help distribute the conductive fillers evenly throughout the material. Homogeneous distribution is important for avoiding fluctuations in electrical properties and potential defects during processing.

• Silane coupling agents: Optimise the bond between silicone and conductive fillers.
• Surface-treated fillers: Special coatings or nanoparticles improve filler distribution and thereby increase material performance.

Which Factors Influence the Electrical Conductivity of Silicone?

In addition to the choice of conductive additives, the material composition and processing method play an important role. Depending on the environment and the subsequent use of the conductive silicone rubber, factors such as temperature, humidity, chemical exposure and mechanical stress may also be relevant.

Type and Amount of Conductive Fillers

The selected fillers have a decisive influence on electrical conductivity. Materials such as silver, copper, graphite and carbon nanotubes differ in conductivity and other properties. Concentration is also important: as a rule, a higher proportion of conductive fillers makes it easier for current to flow.

Distribution of the Fillers

For uniform conductivity, the fillers must be distributed as homogeneously as possible throughout the silicone. Uneven distribution can cause individual areas to conduct differently and reduce material performance. Careful processing is therefore particularly important for individually manufactured moulds and components.

Composition of the Silicone Matrix

Not every silicone formulation responds to conductive additives in the same way. The chemical composition of the base material, as well as other additives or curing agents, influences how effectively the fillers can be incorporated and distributed. Different types of silicone are used depending on the manufacturing process, including LSR silicone for producing precise moulded parts.

Manufacturing and Processing

Processing also affects the subsequent material properties. Important factors include:

• uniform incorporation of the fillers,
• optimum mixing of the components,
• a controlled curing process.

With careful processing, conductivity can be improved while maintaining consistent material properties.

Size and Shape of the Fillers

Particle size and geometry influence how effectively conductive networks form within the silicone. Depending on the application, particles of different sizes or specially treated particles can optimise electrical performance. The desired shape of the finished component can also play a role when selecting the most suitable material for the component.

Environmental Conditions

External influences can also change electrical conductivity.

• Temperature: High or low temperatures can influence conductivity.
• Humidity: Water or high humidity can alter electrical properties, particularly when sensitive fillers are used.
• UV radiation and weathering: Silicone has high resistance to UV radiation and weathering, helping it retain its material properties even after long-term exposure to sunlight and weather.

Material Ageing

Over time, mechanical stress, UV radiation and other environmental influences can change the material structure. As a result, the electrical conductivity of conductive silicone may also change over its service life.