Double-Doped TPU Fibers via Coaxial Wet-Spinning toward Synergistic Thermal Management and Radiative Cooling

Effective personal thermal management, particularly passive cooling without perspiration or energy input, is crucial for enhancing comfort and reducing energy consumption. Heat conduction and radiation represent two key passive cooling mechanisms for textiles, yet concurrently optimizing both remains challenging. Conventional approaches struggle to integrate high-thermal-conductivity fillers like boron nitride nanosheets (BNNS) and high-emissivity materials like silica (SiO2) due to nanoparticle aggregation, uneven dispersion, and functional interference within a single matrix, which compromise performance and spinnability. This work reports a coaxial wet-spinning method to fabricate hydroxyl-functionalized boron nitride nanosheet/silica (OH-BNNS/SiO2) double-doped thermoplastic polyurethane (TPU) fibers. This technique achieves hierarchical functional separation: OH-BNNS confines within the core to enhance thermal conductivity, while SiO2 nanoparticles incorporated into the sheath promote radiative cooling via high mid-infrared emissivity (7–14 μm). Optimized fibers (30 wt % OH-BNNS core) achieve a thermal conductivity of 1.715 W·m–1·K–1 and a 572.55% improvement over pure TPU. The SiO2 sheath provides over 90% visible-light reflectance and reduced mid-infrared reflectance, enabling efficient radiative dissipation. OH-BNNS enhances tensile strength of TPU fiber to 4.68 MPa via hydrogen bonding. OH-BNNS/SiO2 double-doped woven fabric exhibits superior cooling performance (54% lower heating rate than pure TPU under sunlight) and high air permeability (285.9 mm/s under a pressure drop of 100 Pa). This work provides a scalable manufacturing strategy for multifunctional cooling textiles that integrate passive radiative and conductive cooling mechanisms, showing significant potential for energy-efficient personal thermal management.