Preparation of <scp>PP</scp> @ <scp>BN</scp> / <scp>PP</scp> @gr Composite Microspheres via Pickering Emulsion Method and Construction and Properties of Their Gradient Sandwich Thermal Conductive Composites

ABSTRACT This study employed the Pickering emulsion method to coat polypropylene particles with graphite and nano‐boron nitride, designing a composite material with a functional gradient sandwich structure. Thermogravimetric analysis (TG) and scanning electron microscopy (SEM) characterization revealed that graphite and nano‐scale boron nitride were respectively coated onto the polypropylene particle surfaces. The maximum loading capacities of graphite (Gr) and boron nitride (BN) on the PP surface reached 11.86 wt% and 11.85 wt%, respectively. The functionally graded sandwich structure effectively promotes phonon transport while suppressing electron migration. The material exhibits a thermal conductivity of 0.73 W·m −1 ·K −1 and a high volume resistivity of 4.64 × 10 10 Ω·cm, demonstrating dual thermal conductivity and insulation properties. Heat‐up tests conducted on a 100°C hot plate demonstrated that the functional gradient sandwich material reached a surface temperature of 97.3°C within 75 s. Both its heating rate and final steady‐state temperature significantly exceeded those of the control material without the functional gradient structure, directly proving its highly efficient heat transfer performance. This approach offers a novel method for designing advanced thermal management materials, promising to advance the modernization of electronic devices.