Thermal conductivity refers to the ability of a rubber material to transfer heat. It is a measure of how efficiently heat flows through the rubber, typically expressed in watts per meter-kelvin (W/m·K). Rubber generally has low thermal conductivity, making it an effective thermal insulator in many applications.

Key Aspects of Thermal Conductivity in Rubber

1. Definition & Measurement

   • Thermal conductivity is the rate at which heat passes through a material due to a temperature difference.

   • It is measured in W/m·K using methods such as the hot plate test or laser flash analysis.

2. Importance of Thermal Conductivity in Rubber

   • Heat Insulation: Low thermal conductivity helps retain heat or prevent heat transfer, making rubber useful in insulation applications.

   • Temperature Management: Rubber components in machinery, electronics, or automotive applications must manage heat effectively to prevent overheating or thermal degradation.

   • Performance & Safety: Ensures stability of rubber materials when exposed to high or fluctuating temperatures.

3. Typical Thermal Conductivity of Rubber

   • Most rubbers have thermal conductivity in the range of 0.1 – 0.5 W/m·K, significantly lower than metals (e.g., steel: ~50 W/m·K, copper: ~400 W/m·K).

   • Silicone Rubber: Typically 0.2 – 0.3 W/m·K, with variations depending on fillers.

   • Natural Rubber (NR) & Synthetic Rubbers: Usually around 0.15 – 0.25 W/m·K.

4. Factors Affecting Thermal Conductivity

   • Rubber Type: Different elastomers have varying thermal properties.

   • Fillers & Additives: Adding materials like carbon black, graphite, or metallic fillers can enhance thermal conductivity.

   • Crosslinking & Density: More tightly crosslinked rubber has slightly higher thermal conductivity.

   • Temperature & Aging: Heat exposure over time can alter rubber’s thermal behavior due to material degradation.

5. Applications Requiring Low or High Thermal Conductivity

   • Low Thermal Conductivity (Insulating Applications):

     • Seals, gaskets, and coatings for thermal insulation.

     • Electrical cable sheathing to prevent heat transfer.

     • Protective gear and footwear for heat resistance.

   • High Thermal Conductivity (Heat Dissipation Applications):

     • Thermal interface materials (TIMs) in electronics.

     • Heat-resistant rubber pads in industrial machinery.

6. Enhancing or Reducing Thermal Conductivity

   • Increase: Add conductive fillers like carbon black, boron nitride, or aluminum particles.

   • Decrease: Use rubber with high air content (foamed rubber) or add insulating fillers.

Conclusion

Thermal conductivity is an essential property of rubber materials, influencing their ability to insulate or dissipate heat. Most rubbers are naturally low in thermal conductivity, making them good insulators. However, their thermal properties can be modified using additives for applications requiring better heat management.