Superhydrophobic polyvinylidene fluoride/polyimide nanofiber composite aerogels for thermal insulation under extremely h
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Published online 23 November 2020 | https://doi.org/10.1007/s40843-020-1518-4
Superhydrophobic polyvinylidene fluoride/polyimide nanofiber composite aerogels for thermal insulation under extremely humid and hot environment 1
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Fan Yang , Xingyu Zhao , Tiantian Xue , Shijia Yuan , Yunpeng Huang , Wei Fan and 1,2* Tianxi Liu ABSTRACT Excellent thermal insulating materials are highly demanded in various applications including buildings, aerospace and sport equipment. However, in practical applications, the performance of thermal insulating materials usually deteriorates under diverse temperature and humidity conditions. Therefore, it is highly essential to construct a bulk material that exhibits outstanding thermal insulation performance under extremely humid and hot environment. In this work, we have conceived a green and effective strategy to fabricate a superhydrophobic and compressible polyvinylidene fluoride/ polyimide (PVDF/PI) nanofiber composite aerogel via electrospinning and freeze-drying technique. Interestingly, the PVDF nanofibers and PI nanofibers function as the hydrophobic fibrous framework and mechanical support skeleton, respectively, forming a robust three-dimensional framework with good mechanical flexibility. The PVDF/PI aerogel possesses outstanding superhydrophobic feature (water contact −1 −1 angle of 152°) and low thermal conductivity (31.0 mW m K ) at room temperature. Significantly, even at 100% relative humidity (80°C), the PVDF/PI aerogel still exhibits a low thermal −1 −1 conductivity of only 48.6 mW m K , which outperforms the majority of commercial thermal insulating materials. Therefore, the novel PVDF/PI aerogel is promising as an excellent thermal insulating material for the applications in high-temperature and humid environment. Keywords: nanofiber aerogel, polyimide, polyvinylidene fluoride, superhydrophobic, thermal insulation
INTRODUCTION Energy consumption has been a crucial universal issue
due to the rapid industrial development and reduction of fossil energy [1,2]. Thermal insulation is one of the effective ways to decrease energy loss and improve global energy efficiency [3–5]. Excellent thermal insulating materials can find demand in various applications including buildings, aerospace and sport equipment [6,7]. More importantly, the thermal insulating behavior should be stable when materials are exposed outdoor under variable temperature and humid circumstances. However, in practical applications, the performance of thermal insulating materials usually deteriorates under diverse temperature and humidity conditions. For instance, conventional thermal insulating materials, such as polyurethane (PU) and expanded polystyrene (PS), show inferior thermal stability at elevated temperature. On the other hand, the thermal insulating properties of materials are generally compromised when exposed to high humidity environments since water is a highly thermal conductive substance [8,9]. The higher humidity air (i.e., the water molecule) diffusing into the materials woul
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