Ultrasound‐assisted liquid phase exfoliation of boron nitride nanosheets as fillers for polyacrylate pressure‐sensitive adhesives with enhanced thermal conductivity

Hexagonal boron nitride (h‐BN) is widely used as a filler to improve the thermal conductivity of polymers due to the high thermal conductivity, electrical insulation, and chemical stability. However, the small lateral‐size and poor compatibility limit h‐BN's performances and applications in thermal management. Here, boron nitride nanosheets (BNNSs) were prepared by liquid‐phase ultrasonic exfoliation using isopropanol (IPA) as solvent. Specifically, the BNNSs obtained by ultrasonication for 8 h with an initial concentration of h‐BN of 8 mg/mL have the best exfoliation effect and a high yield of 19.8%, showing a large lateral‐size of 1–2 μm and an ultra‐thin thickness. Then, the resulting BNNSs can be modified by grafting silane coupling agent of KH560 (m‐BNNSs), their micromorphology and chemical composition are characterized by various microscopies and spectrometers. Subsequently, polyacrylate pressure‐sensitive adhesives (PSAs) composites are prepared using m‐BNNSs as a thermally conductive filler by UV bulk polymerization, their thermal conductivity can be greatly improved by 250% compared with that of pure PSAs. For comparison, the thermal conductivity of m‐BNNSs/PSAs composites with filler content of 25 wt% is as high as 0.4382 W/(m K), which is 1.6 times higher than that of h‐BN/PSAs composites. In addition, the incorporation of BNNSs will improve the thermal stability, hardness, and 180° peeling force of the PSAs composites, which will stimulate the practical application of PSAs materials.