Hybrid sol-gel-derived method for the synthesis of silicon rubber composites with hBN for characteristic applications in elastomeric thermal pads

Abstract

The thermal conductivity of silicone rubber is very low and does not meet the required thermal conductive applications, so inorganic fillers are added to increase heat transfer which ultimately improves the thermally conductive path. In this study, silicone rubber/hexagonal boron nitride composite was synthesized by the hydrolysis-polycondensation method to enhance the thermal conductivity of the material while retaining acceptable flexibility properties. The introduction of MQ resin reduced crosslink density, thermal stability, tensile strength, and hardness of the silicone resin composite and improved elongation. The addition of vinyl-based MQT and aluminum-based MQT resins improved the properties of the silicone rubber, while the addition of vinyl-based MQT resin reduced the crosslink density, tensile strength and hardness, and improved its elongation and thermal stability properties. While aluminum-based MQT resin did not have a significant effect on crosslink density, tensile strength, or hardness, it also improved elongation and reduced thermal stability. The high filler concentration of hexagonal boron nitride in the composite enhanced thermal conductivity up to 3.253 Wm⁻¹ K⁻¹, while it reduced tensile strength to 1.248 MPa and elongation to 22% but increased hardness up to 75 shore A. The addition of silicone resin improved the thermal conductivity of all MQ, vinyl-based MQT3 and aluminum-based MQT3 resin composites up to 3.661, 3.962 and 4.817 Wm⁻¹ K⁻¹, respectively. For the same three resins, tensile strength was increased up to 1.274, 1.290, and 1.312 MPa, elongation at break was raised to 125%, 188%, and 150%, and hardness was reduced to 69, 71, and 72 shore A, respectively. The addition of silicone resin also showed an effect on density, volatile content, flame resistance, and volume resistivity.