Enhancement of thermal conductivity and mechanical properties of silicone rubber with oriented fillers connected by covalent bonds

Abstract

High-performance thermal interface materials (TIMs) are pivotal for extending the lifespan and ensuring the reliability of electronic devices, due to their excellent thermal conductivity (TC), flexibility, and electrical insulation properties. This study presents an in-depth analysis of the spatial distribution effects of hybrid fillers and proposes an innovative binary-filler synergistic strategy. By combining the unique characteristics of one-dimensional carbon nanotubes (CNTs) and two-dimensional boron nitride (BN), a vertically aligned silicone rubber/boron nitride/carbon nanotubes (SR/KBN/CNTs) flexible TIM was successfully designed and fabricated using a simple molding process. Surface-modified BN was covalently bonded with CNTs, collaboratively forming a continuous thermally conductive network aligned along the heat flow direction within the SR matrix. This structure significantly reduces interfacial thermal resistance and phonon scattering, thereby effectively enhancing the through-plane TC (K_⊥). Specifically, when 50 wt% of the composite filler KBN30/CNTs (KBN: CNTs, 30:1 w/w) was incorporated into the SR matrix, the resulting composite achieved a K_⊥ of 3.57 Wm⁻¹K⁻¹, an increase of 1983% compared to pure SR. Moreover, the composite exhibits a fast thermal response, excellent electrical insulation, and robust thermal stability. This combination of properties highlights its great potential for application in the thermal management of future electronic devices.