Anisotropic Polyimide/Cellulose Nanofibril Composite Aerogels for Thermal Insulation and Flame Retardancy

Abstract

In this study, we report a series of lightweight, anisotropic polyimide/cellulose nanofibril (PI/CNF) composite aerogels with outstanding thermal insulation and flame retardancy via unidirectional drying and freeze drying methods. Along the axial direction, PI/CNF composite aerogels exhibit an arranged tube-like structure in parallel to ice crystal growth, thus providing superior mechanical properties. Conversely, the composite aerogels show a honeycomb-like pore structure along the radial direction, exhibiting excellent elastic properties. More importantly, the addition of CNF endows the composite aerogels with low thermal conductivity along the radial direction. The surface temperature of the composite aerogels with a thickness of 15 mm is 70% lower than that of hot stage annealing at 180 °C for 60 min. Furthermore, the composite aerogels show flame retardant and self-extinguishing performance in the combustion experiment. Therefore, the anisotropic PI/CNF composite aerogels with thermal insulation and flame retardancy are promising for expanding potential applications in aerospace fields.

“Rigid-Flexible” Anisotropic Biomass-Derived Aerogels with Superior Mechanical Properties for Oil Recovery and Thermal Insulation

“…This result could be explained by the fact that the lower density of the aerogel indicates that more air was held in the network of the aerogel, resulting in a thermal conductivity closer to that of air (0.025 W•m −1 •K −1 ). 25 Notably, DF-LCMA exhibited the optimal thermal conductivity (0.02565 ± 0.0024 W•m −1 •K −1 ), which was comparable to the other reported cellulose-based thermal insulation aerogels (Table S4). In addition, the thermal insulation performance between S-DF-LCMA and S-LCMA was compared by placing the obtained aerogel on a heated plate at 200 °C (Figure S11).…”

“…Furthermore, the C1s spectra of S-LCMA are shown in Figure 2d 2e). 25 In addition, as shown in Figure 2f,g, C, O, and Si elements were uniformly distributed on the surface, longitudinal section, and cross-section of S-DF-LCMA, which indicated the overall silylation modification of the aerogel through T-CVD. In addition, the maximum decomposition rate of the aerogel was reduced, and the maximum decomposition temperature was increased after the silylation modification, demonstrating that the thermal stability of aerogels was improved after silylation modification (Figure S3a,b).…”

“…Furthermore, the C1s spectra of S-LCMA are shown in Figure d, and the C1s peak could be divided into three binding forms at 284.62 eV for C–C and CH 3 , 286.59 eV for C–O, and 285.99 eV for C–Si. The high-resolution spectrum of Si2p was composed of three parts, which were 103.07 eV for Si–O–Si, 102.45 eV for C–O–Si, and 102.81 eV for Si–C and Si–O (Figure e) . In addition, as shown in Figure f,g, C, O, and Si elements were uniformly distributed on the surface, longitudinal section, and cross-section of S-DF-LCMA, which indicated the overall silylation modification of the aerogel through T-CVD.…”

“…As shown in Figure a,b, it was found that the thermal conductivity of the as-prepared aerogels was positively correlated with their density. This result could be explained by the fact that the lower density of the aerogel indicates that more air was held in the network of the aerogel, resulting in a thermal conductivity closer to that of air (0.025 W·m –1 ·K –1 ) . Notably, DF-LCMA exhibited the optimal thermal conductivity (0.02565 ± 0.0024 W·m –1 ·K –1 ), which was comparable to the other reported cellulose-based thermal insulation aerogels (Table S4).…”

Additive-Free Method for Enhancing the Volume Phase Transition Rate in Light-Responsive Hydrogels: A Study of Micro-Nano Bubble Water on PNIPAM-co-AAc Hydrogels

“…In particular, aerogels formed with bubble water exhibit a significantly rougher surface characterized by a sponge-like morphology. This textured surface is commonly observed in aerogels prepared by freeze-drying hydrogels and is attributed to the formation of ice nuclei during the freezing phase of the hydrogel [55,56]. The intricate dimensions and characteristics of the surface textures are closely related to the parameters of the freezing and freeze-drying processes employed.…”