Enhancing Thermal Conductivity, Electrical Insulation, and Mechanical Strength of Polydimethylsiloxane Composites with Sandwich Structure

In this article, boron nitride (BN)/carbon nanotube (CNT)/boron nitride (BN) (BCB) film of sandwich structure is prepared by vacuum‐assisted filtration. Compared with the thermal conductivity ( λ ) of BNs–cellulose nanocrystals (CNCs) (BC) film, the λ of sandwich structured BCB films with the same thickness (The preparation process consists of one layer of BC and one layer of CNTs–CNCs (CC) until the completion of three layers of filtration) has been significantly improved. Then, the polydimethylsiloxane (PDMS) matrix is infiltrated into the BCB films by the ultrasonic‐assisted forced infiltration method. Prepared BN/CNT/BN/PDMS (BCBP) composites with sandwich structure have excellent λ and mechanical performance. When the weight ratio of BNs to CNCs is 20:1, the λ of BCBP 20:1 attains 5.253 W (m K) −1 , compared with other thermally conductive composites with the same thickness (0.1 mm), it has an obvious increase. Besides, the dielectric properties and mechanical flexibility of BCBP are also systematically analyzed. This sandwich structure is prepared in such a method that the BCBP will not cause short circuits in electronic devices under high temperatures while having high λ .