Asymmetrically structured nonwoven fabrics with multimodal thermal management and superior flame retardancy for outdoor applications

Maintaining optimal body temperature in cold outdoor environments is crucial for human health and performance. However, developing effective thermal management fabrics for extreme outdoor conditions remains challenging, as it necessitates integrating thermal insulation properties with diversified heating capabilities while ensuring flame-retardant safety. Herein, we report asymmetrically structured multimodal thermal management nonwoven fabrics (MTMNFs) by strategically incorporating carbon black (CB) and silver nanowire (AgNW) functional layer on opposite sides of a flame-retardant phenolic resin meltblown mat (PRMBM) substrate. This design synergistically integrates thermal insulation, solar heating, Joule heating, and radiative heating effects, while maintaining superior flame-retardant properties. The PRMBM demonstrates outstanding thermal insulation properties (thermal conductivity coefficient 0.037 W/m·K) and inherent flame retardancy (LOI=33.96%), providing a robust foundation for multifunctional thermal management. The outer CB layer demonstrates highly efficient photothermal conversion, achieving surface temperatures exceeding 80°C under standard illumination. Simultaneously, the inner AgNW layer provides both efficient Joule heating (reaching 94°C at 3 V) and radiative heating (elevating skin temperature by approximately 3°C) properties. This multifunctional integration, coupled with the substrate's outstanding flame-retardant and thermal insulation properties, establishes MTMNFs as an ideal solution for demanding outdoor thermal management applications. Our approach fundamentally overcomes the limitations of conventional thermal management materials that typically excel in only one specific function and addresses the barriers posed by their lack of flame-retardant safety, thereby providing a highly promising solution for advanced outdoor thermal management materials with broad applications in emergency response, military operations, and recreational outdoor activities.