'Sponge-core' fiber spins a new yarn in thermal comfort

As heatwaves intensify worldwide, a team from Shaanxi University of Science and Technology has spun a fiber that behaves like a thermal sponge. Using a one-step coaxial wet-spinning method, the group encapsulates a polyurethane-modified polyethylene glycol (PUH) core inside a thin cellulose skin. When the fabric is warmed above 50 °C, PUH chains melt and absorb heat; when the surroundings cool, they crystallize and release that energy—yet the porous core slows the exchange, stretching the comfort window from minutes to hours.

Unlike conventional solid-liquid phase-change yarns, which can leak paraffin or PEG after repeated cycles, the PUH formulation undergoes only molecular rearrangement, remaining solid throughout. After 50 heating cycles at 100 °C, the fibers retained more than 90 % of their original 105 J g⁻¹ latent heat and lost less than 1 % mass. Scanning-electron images reveal a sponge-like interior with 47 % porosity that cuts thermal conductivity to 0.115 W m⁻¹ K⁻¹, roughly half that of commercial PET.

Mechanical tests show the yarns tolerate 10 MPa tensile stress and 38 % elongation—robust enough for knitting, weaving or braiding. In laboratory demonstrations, a 3 × 5 cm swatch shielded an electric heater so effectively that its surface stayed 40 °C cooler than an uncovered control. The fabric also prolonged heat release by up to 450 s compared with paraffin-based textiles, suggesting applications in protective clothing, building insulation and even battery-cooling sleeves.

Although the team currently relies on DMAc/LiCl to dissolve cellulose, they note that solvent recycling can mitigate environmental impact. The next step, says corresponding author Chao Duan, is to scale the process to industrial wet-spinning lines and explore bio-derived isocyanates for greener chemistry.

See the article:

DOI

https://doi.org/10.1016/j.jobab.2025.07.005

Original Source URL

https://www.sciencedirect.com/science/article/pii/S2369969825000581

Journal

Journal of Bioresources and Bioproducts