Achieving High Heat Density and Superior Mechanical Strength in Phase Change Fibers for Efficient Personal Thermal Management

ABSTRACT Phase change fibers (PCFs), fibers containing phase change materials, have been recognized as an effective way for personal thermal management. However, achieving PCFs that simultaneously exhibit high heat density and robust mechanical strength remains challenging because of the inherent trade‐off between thermal‐energy storage capacity and mechanical performance. Herein, we utilize a core‐sheath strategy to fabricate aramid nanofiber (ANF)‐based PCFs with a structural ANF sheath layer and a porous ANF core layer filled with phase‐change octadecane. The emulsion‐templated, closed‐cell, highly porous ANF core layer enables good encapsulation and high loading of octadecane, thereby resulting in a high heat density (199.6 J/g). Both the ANF sheath layer and the continuous ANF skeleton in core layer, together with proton donor‐assisted deprotonation in ANF preparation, ensure the superior mechanical strength, with a tensile stress up to 46.6 MPa and a Young's modulus up to 1475.4 MPa. The excellent mechanical property enables the successful weaving of ANF‐based PCFs into fabric demos using an automatic rapier weaving machine. The potential application of such fabrics for rapid cooling and temperature buffering in high‐temperature environments was demonstrated by integrating them into garments for rescue workers and firefighters.