Hygroscopic and cool boron nitride Nanosheets/Regenerated flax fiber material microstructure Dual-Cooling composite...

Developing cooling textiles with unidirectional water transport performances and high thermal conductivities is essential for personal thermal and wet comfort in human activities. We report a green, degradable, hygroscopic cooling material and dual-cooling composite fabric (d-CCF). A boron nitride nanosheet/regenerated flax fiber (BNNS/RFF) material with a high thermal conductivity was prepared by dissolving recovered flax fibers with a green, efficient 1-butyl-3-methylimidazole chloride/dimethyl sulfoxide system and adding BNNSs. The 60- wt% BNNS/RFF materials had excellent thermal conductivity and hydrophilicity, the breaking strength reached 120 MPa, and the elongation was 15.8 %. The d-CCF consisted of cool polyester (CPET) yarn (inner layer), CPET/bamboo composite yarn (middle layer), bamboo yarn, and 60- wt% BNNS/RFF (outer layer) with unobstructed heat dissipation and evaporation cooling for effective moisture and thermal management. This d-CCF had distinct advantages, including a high one-way water transport index (468 %), an extremely high evaporation rate (0.3818 g h^-1), inner layer maximum heat flux (0.191 W cm^-2), and outer layer maximum heat flux (0.249 W cm^-2), providing a cooling sensation upon contact. Compared to cotton fabrics, the d-CCF could keep the skin cooler by 2.5 °C. This work provides a strategy to fabricate environmentally friendly BNNS/RFF materials and a facile pathway for cooling textile development for human health management.