Ultralight air-filled hollow yarn fabrics for efficient thermal insulation and its heat and mass transfer mechanism

Fibrous thermal insulating materials rely on retaining stationary air in their porous structure for effective insulation. However, hollow fibers lose their insulation when turned into textiles due to compression. In this study, we developed connected knitted loop sheaths to create stable hollow yarns. This direct formation allowed immediate use in fabric weaving, avoiding flattening during spinning. Comprehensive experimental analyses examined hollowness, porosity, mass density, and thermal resistance of air-filled hollow (AFH1) yarn fabrics. Results showed remarkable hollowness (41.62%) and porosity (87.509%), effectively trapping stagnant air and enhancing insulation while maintaining a lightweight structure. Computational Fluid Dynamics (CFD) revealed that minor temperature gradients and negligible airflow within the hollow structure minimized heat transfer, resulting in superior thermal insulation performance. These insights aid in designing textiles with hollow yarns for desired insulation and thermal comfort.