Conductive rubber, typically characterized by a resistivity of less than 10^4 Ω·cm, integrates the high elasticity, processability, lightweight nature, and compactness of rubber with metal-like conductive properties. As a crucial functional material, it is widely used in various applications, including electronic devices, electromagnetic shielding, sensors, medical equipment, and the automotive industry.
1. Conductive Rubber Applications
The applications can be summrized into several key areas:
- Electronic Devices: It is widely used in keyboards, touchscreens, and remote controls for their keys and contact points.
- Electromagnetic Shielding: It is used in conductive gaskets and seals to prevent electromagnetic interference (EMI).
- Sensors: Conductive rubber can be utilized to manufacture pressure sensors and tactile sensors.
- Medical Equipment: Used as electrodes, conductive pads, and biosensors in various medical devices.
- Automotive Industry: Applications include static protection, electromagnetic shielding, sensors, touchscreens, and electrical connections.
2. How to achieving conductivity in rubber?
The conductivity of rubber is primarily achieved by incorporating conductive fillers into the rubber matrix. Common conductive fillers include:
- Carbon Black: Adds general conductivity at a lower cost.
- Metal Powders: Such as silver, nickel, or aluminum, provide excellent conductivity and specific functional properties.
Two primary conduction mechanisms in conductive silicone rubber are:
- Carrier Tunneling Effect: Under an electric field, a local electric field forms on the surface of conductive particles, causing carriers to tunnel through, creating conductive paths and enabling charge transfer.
- Carrier Scattering Effect: The uniformity of particle size, shape, distribution, and fill density significantly influences conductive performance.
3. Suitable rubber materials could be produced as conductive rubber
Rubbers with high dielectric constants are preferred to produce conductive rubber. These include:
- Silicone Rubber: Ideal for its conductivity, high and low-temperature resistance, aging resistance, and excellent processing properties.
- Chloroprene Rubber (CR): Good for applications requiring oil resistance.
- Fluorocarbon Rubber (FKM/Viton™): Suitable for oil-resistant environments.
Performance and Cost Comparison of different types Conductive Rubber (Comparison Table):
| Type | Conductivity | Oxidation Resistance | Cost |
|---|---|---|---|
| Carbon-Based Conductive Silicone Rubber | General (Resistivity > 100 Ω·cm) | Moderate | Low |
| Silver-Plated Aluminum Conductive Silicone Rubber | Good (Resistivity 1-100 Ω·cm) | Good | Moderate |
| Silver-Plated Nickel Conductive Silicone Rubber | Excellent (Resistivity 1-100 Ω·cm) | Excellent | High |
| Nickel-Plated Silver Conductive Silicone Rubber | Stable (Resistivity 1-100 Ω·cm) | Excellent | High |
| Silver Powder Conductive Silicone Rubber | Best (Resistivity 1-100 Ω·cm) | Best | Highest |
4. How to enhancing electromagnetic shielding property of conductive rubber?
Electromagnetic shielding effectiveness is influenced by material resistivity, where lower resistivity generally leads to better shielding performance. However, for low-frequency electromagnetic shielding, specific strategies can enhance effectiveness:
- Material Thickness: Increasing the thickness of the conductive rubber can improve low-frequency shielding.
- Layering: Utilizing multiple layers of conductive materials can enhance shielding by providing multiple barriers.
- Conductive Coatings: Applying conductive coatings to surfaces can improve overall shielding performance.
How to measure Electromagnetic Shielding Effectiveness?
Electromagnetic shielding effectiveness (SE) is typically measured in decibels (dB) and represents the logarithmic ratio of the incident to transmitted electromagnetic power. The key methods for measuring SE include:
- Shielding Effectiveness Testing: Measures the attenuation of electromagnetic waves through the shielding material.
- Anechoic Chamber Testing: Provides a controlled environment to evaluate the SE of materials and devices.
- Network Analyzer Testing: Uses a network analyzer to measure the insertion loss and reflectivity of the material.
The effectiveness of electromagnetic shielding is critical in ensuring the proper function and reliability of electronic systems in automotive and other applications.
Appendix 1. Resistivity of some typical type of rubber material:
| Rubber Type | Volume resistivity (Ω·cm) (ISO 1853) |
|---|---|
| Natural Rubber (NR) | (10^{10} – 10^{12}) |
| Synthetic Rubber | |
| – Nitrile Rubber (NBR) | (10^{8} – 10^{12}) |
| – Chloroprene Rubber (CR) | (10^{7} – 10^{10}) |
| – Silicone Rubber (SI) | (10^{14}) |
| – Fluoroelastomer (FKM) | (10^{12} – 10^{15}) |
| Conductive Rubber | |
| – Carbon Black Filled Rubber | (10^{0} – 10^{2}) |
| – Metal Filled Rubber | (10^{-3} – 10^{1}) |
| Anti-static Rubber | |
| – Carbon Black or Other Fillers | (10^{4} – 10^{8}) |
| Super Conductive Rubber | |
| – High Conductive Fillers | (10^{-3} – 10^{0}) |
OBT has developed the conductive rubber with carbon nanotube which could achieve resistivity less than 100 Ω·cm.Please conact with us for better understanding of your technical requirement.
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