Continuous, Strong, Porous Silk Firoin-Based Aerogel Fibers toward Textile Thermal Insulation

Abstract

Aerogel fiber, with the characteristics of ultra-low density, ultra-high porosity, and high specific surface area, is the most potential candidate for manufacturing wearable thermal insulation material. However, aerogel fibers generally show weak mechanical properties and complex preparation processes. Herein, through firstly preparing a cellulose acetate/polyacrylic acid (CA/PAA) hollow fiber using coaxial wet-spinning followed by injecting the silk fibroin (SF) solution into the hollow fiber, the CA/PAA-wrapped SF aerogel fibers toward textile thermal insulation were successfully constructed after freeze-drying. The sheath (CA/PAA hollow fiber) possesses a multiscale porous structure, including micropores (11.37 ± 4.01 μm), sub-micron pores (217.47 ± 46.16 nm), as well as nanopores on the inner (44.00 ± 21.65 nm) and outer (36.43 ± 17.55 nm) surfaces, which is crucial to the formation of a SF aerogel core. Furthermore, the porous CA/PAA-wrapped SF aerogel fibers have many advantages, such as low density (0.21 g/cm3), high porosity (86%), high strength at break (2.6 ± 0.4 MPa), as well as potential continuous and large-scale production. The delicate structure of multiscale porous sheath and ultra-low-density SF aerogel core synergistically inhibit air circulation and limit convective heat transfer. Meanwhile, the high porosity of aerogel fibers weakens heat transfer and the SF aerogel cellular walls prevent infrared radiation. The results show that the mat composed of these aerogel fibers exhibits excellent thermal insulating properties with a wide working temperature from −20 to 100 °C. Therefore, this SF-based aerogel fiber can be considered as a practical option for high performance thermal insulation.

Recent Progress in Polysaccharide Aerogels: Their Synthesis, Application, and Future Outlook

“…The pore size significantly influences the mechanism of heat transfer via thermal conduction. Aerogels contain a gas phase that decreases the amount of collisions between the molecules, thus decreasing the thermal conductivity and limiting convective mass transfer [ 31 , 36 ]. The thermal conductivity decreases with an increase in the density and a decrease in the porosity.…”

“…The density of an aerogel can be as low as 0.004–0.5 g/cm 3 with a high porosity of up to 99.8% and a large specific surface area of 100–1600 m 2 /g [ 11 ]. Due to these properties, the aerogels have been applied as adsorbents of CO 2 [ 12 , 13 , 14 , 15 , 16 ], dyes, and heavy metals [ 2 , 3 , 11 , 17 , 18 , 19 , 20 , 21 , 22 , 23 ], as tissue engineering and blood system scaffolds in the biomedical field [ 3 , 22 , 23 , 24 , 25 , 26 , 27 ], and as materials for thermal insulation [ 4 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 ] and food packaging [ 37 , 38 , 39 , 40 , 41 ]. These versatile materials also exhibit high optical transparencies, low thermal conductivities (down to 12 mW/mK) and low sound speeds [ 42 , 43 ].…”

Robust Silica-Bacterial Cellulose Composite Aerogel Fibers for Thermal Insulation Textile

“…The stress–strain curves of CAFs obtained from tensile tests showed that the breaking stress was in the range of 4.5–5.4 MPa. All the samples showed good tensile strength, which was much higher than that of native silica aerogel fibers, and it was comparable or even superior to those of CA/PAA-SF aerogel fibers [ 41 ] (3 MPa), SF/GO aerogel fibers [ 36 ] (3.2 MPa), and PAO@ANF aerogel fibers [ 28 ] (4.56 MPa). Moreover, the curves also showed that the elongation at break of the sample decreased from 6.8% to 1.1% with increasing precursor concentration.…”

Multichannel and Super-flexible SiZrOC Ultrafine Fibers for High Temperature Thermal Insulation

“…Recently, it has been found that constructing porous structure is an effective way to reduce the thermal conductivity of fibers [18][19][20][21][22]. On the one hand, the porous structure will lengthen the path of heat transfer and hinder the gaseous heat conduction, leading to a low solid and gas heat transfer [18,19].…”