Hierarchically porous coaxial wet-spun cellulose/polyurethane based hexamethylene diisocyanate (PUH) solid-solid phase change fiber for enhanced thermal management

In the present study, we innovatively construct a porous sponge-like solid-solid phase change fiber (SSPCF) based on one-pot coaxial wet spinning process. For the core-sheath SSPCF, cellulose serves as the sheath precursor, while an isocyanate modified polyethylene glycol (PEG), namely polyurethane-based hexamethylene diisocyanate (PUH), acts as the core solid-solid phase change material (SSPCM). Upon the non-solvent induced phase separation (NIPS) during the wet spinning, the unique SSPCF with thin and dense sheath yet thick and porous sponge-like core were successfully fabricated, and they exhibited excellent slow heat release, high-temperature thermal protection. It is hypothesized that the porous structure within the fiber core primarily accounts for the superior temperature control heat release behavior and thermal insulation capability. Additionally, the prepared SSPCFs demonstrate high phase change enthalpy (105.26 J/g), high strength (10.38 MPa), excellent leak-proof and cyclic stability. Compared to solid-liquid phase change fibers (enthalpy: 110.7 J/g) and commercial polyethylene terephthalate (PET) fibers, the thermal response time (900 s) of the SSPCFs is extended by 300 s and 755 s, while their heat release time (450 s) is increased by 127 and 347 s, respectively. This research provides inspiration for the development of high-temperature insulation and slow heat release functional fibers and fabrics.