Highly stretchable phase change fibers from coaxial wet spinning of nonaqueous emulsions for temperature regulation

Although phase change fibers have proven to be highly potential for a variety of applications, the rigidity of solid–liquid phase change material in its solid state hinders the fabrication of highly stretchable phase change fibers. In this work, we report a strategy of encapsulating phase change material (octadecane, OD) in thermoplastic polyurethane (TPU) based on a nonaqueous emulsion (OD-in-TPU solution), which serves as the core layer liquid in coaxial wet spinning. The use of TPU solution as the outer layer liquid provides an extra cover for the core layer of TPU dispersed with OD. The resulting core-sheath structured phase change fibers exhibited excellent flexibility, stretchability and elasticity, with the tensile strain at break up to 623.9 % and ultimate stress up to 3.5 MPa. The fibers showed heat absorption and release temperatures ranging from 30.7 to 32.0 °C and from 21.6 to 22.3 °C, respectively, similar to that of bulk OD. In particular, the fibers possessed much reduced OD leakage in comparison to fibers from conventional methods, and the fibers exhibited extremely high heat capacity (up to 187.8 J/g), without obvious deterioration observed in heat capacity after 100 heating–cooling cycles. Simple fabrication, excellent stretchability, high heat capacity, and reusability enabled such phase change fibers to be highly promising for practical use in temperature regulation.