Conductive silicone is a polymer composite material with both elastomer properties and conductive functions. It achieves conductive properties by adding conductive fillers (such as metal particles, carbon materials, conductive fibers, etc.) to the silicone rubber matrix, while retaining the flexibility, weather resistance and chemical stability of silicone. Its core characteristics, preparation process and application areas are as follows:
1. Core characteristics
Conductive properties
A three-dimensional conductive network is formed through conductive fillers to achieve isotropic or anisotropic conductivity.
The volume resistivity can be as low as 10⁻²~10⁰ Ω·cm, and the surface resistivity can reach below 10⁵ Ω/□ (electromagnetic shielding level).
Common conductive fillers: silver powder, copper powder, nickel-coated graphite powder, carbon black, carbon fiber, etc.
Mechanical properties
Tensile strength: 5~10 MPa
Elongation at break: 300%~800%
Hardness (Shore A): 25~60 degrees, which can be adjusted according to needs.
Environmental adaptability
Temperature range: -60℃~200℃ (special formula can reach 300℃)
Weather resistance: UV resistance, ozone resistance, aging resistance.
Chemical corrosion resistance: good tolerance to acids, alkalis, solvents, etc.
Electromagnetic shielding and sealing performance
When the volume resistivity is lower than 10 Ω·cm, it has electromagnetic shielding function, and the shielding efficiency can reach 40 GHz.
Excellent water vapor sealing performance, suitable for high pressure and humid environment.
2. Preparation process
Base material
Methyl vinyl silicone rubber (VMQ) is used as the base rubber, and additives such as vulcanizer and cross-linking agent are added.
Selection of conductive filler
Metal filler: silver powder (best conductivity, high cost), copper powder (easy to oxidize), nickel-coated copper powder (strong oxidation resistance, high cost performance).
Carbon filler: carbon black, carbon fiber, graphene (low cost, moderate conductivity).
Composite filler: silver-coated glass beads, nickel-plated graphite, etc., taking into account conductivity and cost.
Mixing and molding
Mixing: Mix silicone rubber, conductive filler and additives evenly in an internal mixer or an open mixer.
Molding process:
Compression molding: Suitable for complex structural products (such as conductive buttons and seals).
Extrusion molding: Used to produce continuous profiles (such as conductive rubber strips and hoses).
3D printing: An emerging technology in recent years that can achieve customized complex structures.
Vulcanization: Give the material elasticity through platinum vulcanization or peroxide vulcanization.
3. Application fields
Electronic and electrical
Conductive connectors: Replace traditional metal connectors to achieve flexible circuit connection.
Electromagnetic shielding: Used for electromagnetic sealing of electronic equipment such as chassis, cabinets, and shelters.
Antistatic components: Antistatic trays and packaging materials for manufacturing electronic components.
Communication equipment
5G base stations: Used for antenna sealing and filter shielding.
Handheld terminals: Keys and interface sealing of mobile phones and tablets.
Automotive electronics
Sensors: Conductive sealing for pressure sensors and temperature sensors.
High-voltage connectors: Conductive seals for new energy vehicle battery packs.
Aerospace
Spacecraft sealing: used for electromagnetic shielding and sealing of satellites and spacecraft.
Radiation-resistant components: conductive sealing materials in nuclear power plants and high-radiation environments.
Medical equipment
Artificial organs: conductive sealing of pacemakers and neurostimulators.
Wearable devices: flexible conductive electrodes and biosensors.
4. Technical challenges and development trends
Technical challenges
Balance between conductivity and mechanical properties: high conductivity requires high filler content, but it will reduce tensile strength and elongation.
Long-term stability: metal fillers are easily oxidized, and anti-oxidation coatings or composite fillers need to be developed.
Cost control: silver powder is expensive, and low-cost alternatives such as nickel-coated copper powder need to be promoted.
Development trends
Multifunctionality: development of multifunctional integrated materials such as conductive, thermally conductive, flame-retardant, and antibacterial.
Nanotechnology: use nanomaterials such as graphene and carbon nanotubes to improve conductivity and mechanical properties.
Environmental protection: use water-based conductive coatings and halogen-free flame retardants to meet environmental regulations such as RoHS and REACH.
Smart manufacturing: Combined with 3D printing and automated production lines, customized and efficient production is achieved.
5. Typical product examples
Conductive silicone buttons
Used in remote controls, calculators, etc., to achieve switch-on through compression force.
Hardness 40~60 Shore A, resistivity 10²~10⁴ Ω·cm.
Conductive rubber strips
Used for sealing electronic equipment housings, with both conductive and waterproof functions.
Volume resistivity <10 Ω·cm, temperature resistance -50℃~200℃.
Electromagnetic shielding pads
Used for EMI shielding of chassis and cabinets, shielding effectiveness >60 dB (10 MHz~18 GHz).
Flexible circuit boards
Used in wearable devices and flexible displays to achieve stable conductivity under bending conditions.
Thickness 0.1~1 mm, resistivity of conductive layer <10⁻³ Ω·cm.