Robust Silica–Polyimide Aerogel Blanket for Water-Proof and Flame-Retardant Self-Floating Artificial Island

Abstract

A robust silica–polyimide (PI) aerogel blanket is designed and synthesized using the PI foam as the matrix and silica aerogel as the filler through an in situ method, where sol–gel transition of silica precursor occurs in pores of the PI foam, followed by the hydrophobization and ambient pressure drying. The density of the aerogel blanket ranges from 0.036 to 0.196 g/cm3, and the low density is directly controlled by tailoring the silica concentration. The specific surface area of the aerogel blanket reaches 728 m2/g. These features of the blanket result in a low thermal conductivity of 0.018 W/mK, which shows a remarkable reduction of 59% compared to that of the PI foam (0.044 W/mK). As a result, a remarkable decrease of 138°C is achieved using the silica blanket as the thermal insulator on a hot plate of approximately 250°C. In addition, the temperature degradation of the blanket is around 500°C, and up to 86% of mass remaining at 900°C is obtained. The blanket is resistant at extremely harsh conditions, e.g., 600°C for 30 min and 1,300°C for 1 min, and no open flame is observed, suggesting a significant flame-retardant of the blanket. Owing to the three-dimensional (3D) porous framework of the PI foam, the silica aerogel is encapsulated in the PI foam and the blanket exhibits strong mechanical property. The silica–PI aerogel can be reversibly compressed for 50 cycles without reduction of strain. The contact angle of the blanket is 153°, which shows a superior waterproof property. Combining with the low density, low thermal conductivity, flame-retardant, and strong mechanical strength, the aerogel blanket has the potential as an artificial island, which is safe (waterproof and flame-retardant), lightweight, comfortable, and easy to be moved.

Novel, flexible, and transparent thin film polyimide aerogels with enhanced thermal insulation and high service temperature

“…Furthermore, compared to S1M, the S2M sample had a considerable weight loss after 40 seconds, which contributed to the DMBZ with the lower onset of decomposition in the backbone. Overall, such a flame-retardancy behaviour of fabricated PI aerogels in this work is in accordance with the one reported for PI-PVDF aerogels, 91 PI-silica aerogels, 92 and nanocellulose xerogels. 93 A DSC test was performed on fabricated PI aerogels.…”

“…Another potential reason could be the evaporation of residual solvents, i.e., NMP and adsorbed water, as explained by Simo ´n-Herrero et al 87 Apart from excellent thermal stability, benefiting from an imide ring (-CO-NH-CO-) in PI aerogel backbones, they are known to have a self-flame retardant property. 90 In order to demonstrate such behaviour, a simple alcohol burner lamp with an approximate flame temperature of B650 1C (similar to the one reported in the literature 91,92 ) was utilized. As can be seen in Fig.…”

Thermal Conductivity of Nanoporous Materials: Where Is the Limit?

“…30 mW/(m K), normally as a result of the higher fraction of macropores originated by the organic moieties in the silica backbone (when using the co-precursor method) or/and by the presence of fibers as reinforcement. Numerous works compiled in Table 4 report the development of silica-fiber aerogel composites [65,67,68,70,74,75,79]. In fact, this strategy is very efficient in making larger aerogels that have better machinability.…”

“…Some works, however, report silica aerogels without reinforcement (polymers or fibers) [69,71,72,76,78]. Regarding the processing, the majority of works compiled in Table 4 were prepared with TEOS as silica source (or as a co-precursor) [66,67,69,71,[73][74][75][76][77][78][79][80][81]. Ambient pressure drying (i.e., evaporation of the solvent at ambient pressure) is also becoming more common in superinsulating materials [66,69,[72][73][74]77].…”

Design, Synthesis, and Use of High Temperature Resistant Aerogels Exceeding 800 oC

“…For example, carbon materials cannot be used as precursors for HTRAs, such as graphene and carbon nanotubes (CNT), because they will undergo oxidative decomposition in an aerobic conditions at high temperatures. [41,42] Polymers [43][44][45][46][47][48][49][50][51][52][53] cannot be used as candidate precursors neither, although some aromatic heterocyclic polymers exhibit thermal stability in an oxygen-free thermal decomposition temperature up to 550 ℃ (e.g. polyimide aerogels and aramid aerogel).…”