Ambient Pressure Drying to Construct Cellulose Acetate/Benzoxazine Hybrid Aerogels with Flame Retardancy, Excellent Thermal Stability, and Superior Mechanical Strength Resistance to Cryogenic Temperature

Abstract

Cellulose aerogels are highly attractive candidates in various applications, such as thermal insulation, adsorption separation, biomedical field, and as carriers, due to their intrinsic merits of low density, high porosity, biodegradability, and renewability. However, the expensive cost of the supercritical drying process and poor mechanical properties limit their practical applications. Herein, a new method was presented to fabricate cellulose acetate/benzoxazine hybrid aerogels (CBAs) with low cost, low drying shrinkage, excellent mechanical properties under cryogenic condition (−196 °C), outstanding thermal insulation, flame retardancy, and good thermal stability by ambient pressure drying. In more detail, the weighted drying shrinkage rate of CBAs-T2 can be controlled to 6.8% (the average value along the radial and axial directions), mainly due to the enhanced skeleton, by introducing polybenzoxazine networking chains. The resultant CBAs-T2 exhibit outstanding mechanical properties at room temperature because of the presence of the polybenzoxazine hybrid in the cellulose networking system. CBAs-T2 still have good mechanical properties even after subjecting them to liquid nitrogen treatment. In addition, the optimal value of thermal conductivity (0.033 W m −1 K −1 ) is gained easily because of the uniform cross-linking networking structure and small pore size. A superior flame retardance of CBAs-T2 is endowed to achieve self-extinguishment after ignition, which is attributed to the presence of the aromatic ring in the backbone structure. Moreover, the good thermal stability of CBAs-T2 is attributed to the fact that polybenzoxazine components could resist the decomposition of cellulose acetate and inhibit heat release during the combustion process. Our study would provide a novel method for obtaining biomass aerogels including the cellulose-based materials system with low drying shrinkage and superior mechanical properties despite bearing a cryogenic environment by the low-cost ambient pressure drying approach.

Preparation and Characterization of Cellulose Nanofibers/Polybenzoxazine–Poly(vinyl alcohol) Double Network Foam Based on Multiple Hydrogen Bond Structure

“…In contrast, the alcohol −OH absorption peak at 3430 cm –1 in CNFs–PVA is weaker, possibly indicating that most of the active −OH groups on the surface of CNFs form hydrogen bonds with PVA. Peaks at 2930, 1428, and 1265 cm –1 arise from C–H, aromatic ring, and −Ph–O–C– stretching vibrations, respectively, indicating the presence of aromatic compounds in the long molecular chains of all three samples. Moreover, CNFs–PVA and CNFs/PBZ–PVA foams share two common characteristic peaks.…”

Thermal insulation and mechanical properties of carbon fiber‐reinforced thermoplastic polyphthalazine ether sulfone ketone composites reinforced by hollow glass beads

“…Therefore, according to the heat bridge theory, heat should be preferentially conducted through CF when passing HGB/CF/PPESK composites. When heat is transferred parallel to the fiber direction (Figure 4A), CF form a through‐conduction “highway” that enables rapid heat transfer from the higher temperature side to the lower temperature side 37,38 . However, when heat is conducted perpendicular to the fiber direction (Figure 4B), CF can guide part of the heat to both sides of the material, resulting in a lower thermal conductivity, which can well explain the phenomenon that the thermal conductivity parallel to the fiber direction is much higher than that perpendicular to the fiber direction.…”

Cellulose Diacetate Aerogels with Low Drying Shrinkage, High-Efficient Thermal Insulation, and Superior Mechanical Strength

“…The microstructure, drying shrinkage, thermal insulation, and mechanical properties of CDAAs were systematically investigated. Benefiting from the introduction of tert-butanol, the CDAAs retained their porous structure during solvent removal under the interaction of tert-butanol solvent polarity, which resulted in a minimal drying shrinkage (1.4%) of CDAAs before and after the drying process compared with those of the other studies [28][29][30]. The thermal conductivity of 0.021 W m −1 K −1 at ambient temperature and pressure suggested the presence of moderate nanoporous structures and the corresponding excellent thermal insulation property of CDAAs.…”

“…On the basis of our previous work [ 28 , 29 ], we proposed a facile preparation method to construct a kind of high-performance cellulose acetate aerogel (CDAA) by the crosslinking of cellulose diacetate and 2, 4-toluene diisocyanate, which experiences the aging process, a tert-butanol solvent exchange, and finally supercritical carbon dioxide. The microstructure, drying shrinkage, thermal insulation, and mechanical properties of CDAAs were systematically investigated.…”