Electrically insulative and thermally conductive hydrophobic composite sheets based on cellulose nanofibers for thermal interface applications

Abstract Thermal interface applications with biodegradable materials are one of the priority areas of research. In this study, supernatant cellulose nano‐fibers (SCNF) were synthesized and optimized with the functionalized hexagonal boron nitride (h‐BN). The fabricated nanocomposite sheets of SCNF and h‐BN have been characterized for structural, chemical, physical, thermal stability, thermal, and electrical transport properties. Different compositions of the samples have been performed, and the modified h‐BN: SCNF = 30:70 sample showed the best results. The contact angle of 95.2° highlights the hydrophobic properties of the nanocomposite, which makes it suitable for moisture resistance applications. The BN‐OH30/SCNF70 (modified h‐BN: SCNF = 30:70) nanocomposite sheets show an in‐plane thermal conductivity of 19.76 W/m·K and an out‐plane thermal conductivity of 0.96 W/m·K. Its electrical resistivity exceeds 400 × 10 ⁶ ohms·cm. The composites have low dielectric constants at high frequencies, making them ideal for next‐generation electronics that require minimal energy losses along with excellent frequency stability. The nanocomposite sheets show increased thermal stability, moisture resistance, heat transport properties, and electrical resistivity to the SCNF, which shows the potential use for thermal interface applications.