Abstract: With increasing awareness of energy consumption and sustained focus about comfort and health issues, there has been widespread research interest in thermal management textiles that reduce an individual’s body temperature in high-temperature environments. Thermal comfort is a psychological state that expresses satisfaction with the thermal environment. It is important to maintain thermal comfort because the thermal state of the human body is crucial to physiological and mental health and if the core body temperature reaches a hyperthermic condition ranging from 37.5℃ to 38.3℃, or a low temperature below 35.0 ℃, it is potentially life-threatening to humans. Clothing is the most widely used microclimate regulating material in human activities. Protection against high temperature weather can be achieved by developing passive radiative cooling fabrics (PRCF).
In this paper, nano zinc oxide particles (ZnO-NPs) and polypropylene (PP) were used as raw materials to perform melt blending, granulation, slicing and drying. Firstly, the basic properties of the raw materials were studied, and mainly characterized by Fourier transform infrared spectrum, UV reflectivity and melt index of the granules. Subsequently, ZnO-NPs/PP granules were used for melt spinning to prepare ZnO-NPs/PP radiative cooling filaments, and the spinnability properties of ZnO-NPs/PP with different mass fractions were studied. The filaments were also drawn, and the effect of the corresponding drawing process on the mechanical properties of the filaments was studied. In addition, the thermal properties and surface morphology of the filaments were characterized in detail. Finally, the filaments were used to weave fabrics on a sample weaving machine, and the indoor and outdoor radiation cooling performance of the fabrics was evaluated.
Research results show that ZnO-NPs/PP materials have high reflectivity in the solar spectrum range and exhibit excellent emissivity in the atmospheric window band. As can be seen from SEM images, the fiber surface is smooth without defects such as pores and depressions. However, as the mass fraction of ZnO-NPs increases, it may lead to agglomeration or aggregation of ZnO-NPs, thus affecting the stability and continuity of the spinning process. In addition, 0.25% ZnO-NPs/PP filaments exhibit excellent mechanical properties and thermal stability. At the same time, the addition of ZnO-NPs also improves the thermal stability of the filaments. In addition, the woven fabric was tested for indoor and outdoor radiation cooling performance. The results show that compared with cotton fabric, this fabric can lower the temperature by 1.1 ℃ indoors and 4.5 ℃ outdoors.

Key words: ZnO-NPs, radiation cooling, melt spinning, filament, spectrum selective fabrics

摘要： 在高温环境中，能够降低个体体温的热管理纺织品引起了人们的广泛关注。利用纳米氧化锌颗粒(ZnO-NPs)和聚丙烯(PP)作为原材料，通过熔融纺丝制备了具有辐射降温功能的长丝(ZnO-NPs/PP材料)，并将其编织成织物。测试了原材料的基本性质、无机纳米颗粒的分散性、ZnO-NPs/PP长丝的性能以及织物的室内外降温效果。结果显示：ZnO-NPs/PP材料在太阳光谱范围内具有较高的反射率，在大气窗口波段则展现出良好的透过率；当ZnO-NPs/PP中的ZnO-NPs质量分数增加时，ZnO-NPs的团聚加剧，影响熔融纺丝的稳定性。此外，对ZnO-NPs/PP织物进行的室内外辐射降温性能测试表明：与传统棉织物相比，该织物在室内可实现约1.1 ℃的降温效果，在室外则可达到4.5 ℃的降温效果。

关键词: 纳米氧化锌颗粒(ZnO-NPs), 辐射降温, 熔融纺丝, 长丝, 光谱选择织物