Reprocessable xPDMS/h-BN Cooling Composites Enabled by Dynamic Siloxane Bond Exchange

Passive radiative cooling materials have attracted increasing attention as energy-efficient thermal management solutions for outdoor applications. However, most conventional cooling materials are based on permanently crosslinked polymer networks, limiting their reprocessability after curing. In this study, reprocessable xPDMS/h-BN cooling composites were developed by introducing a dynamic siloxane network capable of thermal bond exchange. The resulting composites exhibited vitrimer-like behavior, enabling repeated reshaping through thermal processing while retaining their structural integrity. The incorporation of h-BN improved the optical and thermal characteristics required for passive cooling applications. Although excessive filler loading led to a reduction in toughness, composites containing up to 20 wt% h-BN maintained sufficient flexibility for practical use. Furthermore, the cooling functionality was largely preserved after multiple reprocessing cycles, despite the formation of surface wrinkles induced by repeated thermal treatment. These findings demonstrate that the proposed xPDMS/h-BN system offers a promising strategy for combining passive cooling performance with reprocessability. The developed cooling composites may provide opportunities for sustainable thermal management applications in metallic exterior surfaces and outdoor equipment housings requiring long-term serviceability and repairability.