Because of the higher and higher requirements for the warmth, portability and functionalization of cold-proof clothing, the demand for its basic material: warm fiber is also getting higher and higher. The application potential of natural fiber and traditional chemical fiber has almost been developed, so it is necessary to innovate the structure of traditional chemical fiber in order to obtain better thermal performance. In the 1950s, the American DuPont Company developed profiled fibers, and the glossiness and fluffiness of chemical fibers have been greatly improved. Among the many special-shaped fibers, the hollow fiber significantly improves the thermal insulation performance of the chemical fiber because it significantly increases the content of still air in the hollow fiber. In the 1970s, researchers developed ultra-fine fibers. Artificial leather and other biomimetic materials made of ultra-fine fibers make the thermal properties of chemical fibers equal to those of natural materials. Through the study of hollow fiber and ultra-fine fiber, it is found that the thermal insulation performance of fiber material is directly proportional to the static air content in the fiber material, inversely proportional to the fiber diameter and inversely proportional to the overall material density. Aerogel fiber has the remarkable characteristics of extremely high porosity and ultra-low density. In theory, aerogel fiber is a kind of fiber with the best thermal insulation effect, which is expected to replace ultra-fine fiber or even subvert down, and is the most important development direction of the next generation of thermal insulation fiber. However, the preparation of aerogels is faced with great challenges because of its high porosity.
Picture, Kevlar aerogel fiber
In view of this, the aerogel team led by Zhang Xuetong, a researcher at Suzhou Institute of Nanotechnology and Nano Bionics, Chinese Academy of Sciences, obtained nanofiber dispersions by dissolving Kevlar fibers of DuPont TM, and then prepared a Kevlar aerogel fiber with high porosity (98%) and high specific surface area (240m2/g) by wet spinning and special drying, as shown above. The aerogel fiber has excellent mechanical properties and can be bent, knotted, woven and so on. The aerogel fiber also has excellent thermal insulation properties, the thermal conductivity is only 0.027W/ m ·K at room temperature, and its thermal insulation performance is 2.8 times higher than that of cotton cloth at low temperature. It can exert thermal insulation performance for a long time in the extreme environment of-196~300oC. In addition, the aerogel fiber has excellent chemical stability and can be modified by dyeing, hydrophobization and electroless plating without damaging the main skeleton structure of the aerogel. Finally, the aerogel fiber can also be prepared into air-conditioning fiber by filling phase change materials, and its enthalpy can reach 162J shock g, which is much higher than that of the existing commercial Outlast air-conditioning fiber. The related results are published in the international journal ACS Nano (DOI:10.1021/acsnano.9b01094) under the title of "NanofibrousKevlarAerogelThreadsforThermalInsulationinHarshEnvironments". Liu Zengwei, a doctoral student, and Lu Jing, a postdoctoral student, are the co-first authors of the paper, and researcher Zhang Xuetong is the correspondent author of the paper. The work of this paper is supported by the National Natural Science Foundation of China, the National key Research and Development Program and the Royal Society-Newton Advanced Scholars Fund. Chemical&EngineeringNews (C&EN) of the United States reported the team's research results under the title of "Kevlar, the tough material used in body armor and sporting gear,now comes in aerogel form".
The website is as follows: https://cen.acs.org/materials/polymers/Kevlar-tough-material-used-body/97/i19
