Stretchable Thermoplastic Polyurethane/Boron Nitride Nanosheet Fabrics with Highly Anisotropic Thermal Conductivity for Multi-scenario Passive Radiative Cooling

Abstract

Passive radiative cooling fabrics with high solar reflectance and mid-IR emissivity hold great promise for personal cooling applications. Nevertheless, most current passive radiative cooling fabrics overlook their inherent thermal conductivity, resulting in ineffective heat transfer from human skin to the environment. Herein, by constructing highly anisotropic thermal conductive thermoplastic polyurethane/boron nitride nanosheet (TPU/BNNS) fabrics via one-step electrospinning, thermal conductive cooling mechanism was introduced into passive radiative cooling fabrics. The stacked TPU/BNNS nanofibers with aligned BNNS along the fiber direction and the porous fiber network with high contact thermal resistance resulted in high thermal conductivity along the in-plane direction but low thermal conductivity along the out-of-plane direction. This high anisotropy enables rapid heat transfer along the in-plane direction to dissipate heat while blocking external heat penetration along the out-of-plane direction, thus achieving an effective conductive cooling effect. Moreover, the incorporation of BNNS increased the scattering sites for solar radiation, further improving the fabric’s solar reflectivity to 95%. Combined with the high emissivity (92.9%) provided by the intrinsic groups of TPU and BNNS, the fabric demonstrates excellent radiative cooling ability. Therefore, under the dual action of passive radiative cooling and conductive cooling, the TPU/BNNS fabric achieved a sub-environmental cooling of 12.4 °C and a personal cooling of 10.7 °C. Along with excellent breathability, stretchability, and waterproof properties, the TPU/BNNS fabric exhibits outstanding potential for outdoor personal thermal management applications.

Graphical Abstract