Lightweight and Flexible Phenolic Aerogels with Three-Dimensional Foam Reinforcement for Acoustic and Thermal Insulation

Abstract

Organic aerogels with low density and developed porosity are extremely attractive for use in high-performance insulation, but their complicated fabrication, brittle structure, and poor flame retardancy greatly limit their practical applications. Herein, we report the preparation and properties of a lightweight and flexible phenolic aerogel reinforced with three-dimensional melamine foam (MF) through sol−gel polymerization of commercially available phenol formaldehyde. The wet gels with macroporous porosity and a strong network could be dried at ambient pressure without any volume shrinkage, which is extremely prior to the complicated supercritical drying. The introduction of MF can serve as a flexible skeleton to improve mechanical properties and simultaneously enhances the flame retardancy of aerogels. Additionally, the inherent excellent acoustic and thermal insulation properties of aerogels are maintained. The obtained aerogel possesses a low density (∼0.112 g•cm -3 ), high flexibility, excellent flame retardancy, hydrophobic property (135°), and acoustic and thermal insulating property (0.021 W•m −1 •K −1 at room temperature). The current work may provide a simple, scalable, and economical approach for advancing the fabrication of organic aerogel materials for various applications.

Melamine‐Crosslinked Polyimide Aerogels from Supercritical Ethanol Drying with Improved In‐Use Shape Stability Against Shrinking

“…Due to their unique nano-porous nature, ultralight densities, low thermal conductivity, etc., polymer aerogels have received a lot of attention in the fields of thermal insulation, catalysis, waste disposal, and so on. [1][2][3][4] Up to now, there are a DOI: 10.1002/mame.202100645 wide variety of polymer aerogels available, such as those derived from phenolic resins (PR), [5] polybenzoxazines (PBO), [6,7] polyureas (PUA), [8] Kevlarlike polyamides (PPTA), [9,10] polyimides (PI), [11][12][13] polyurethanes (PU), [14] etc. Among them, PI aerogels are very attractive due to their superior mechanical and thermal insulation properties, and can find diverse applications such as extravehicular activity (EVA) suits, thermal protective systems (TPS), submarine sound barrier systems, etc.…”

Chitosan Based Aerogels with Low Shrinkage by Chemical Cross-Linking and Supramolecular Interaction

“…The relatively low shrinkage of the CPAs can be attributed to the crosslinker (OPA) and linear PVA polymer, which bonded to the rigid benzene ring and provided the supramolecular interaction. Moreover, the inter/intramolecular physical entanglement of NFC may have further controlled the shrinkage; the radial and axial shrinkage of the CPNAs-37.5 was only 14.74% and 15.79%, respectively, which was lower than previously reported for CTS based aerogels [ 28 ] and traditional CTS aerogel, which can be as high as 50% [ 35 ]. Fortunately, the shrinkage of the CPNAs was sharply restricted within ~15% along the radial and axial directions, which was due to the trussed effect by NFC chains and linear PVA chains.…”

“…Thus, a crucial phenomenon was found in which the absorbance strength in the CPNAs was apparently enhanced at 1656 cm −1 compared with that of CTS, corresponding to the stretching vibrations of C=N in nature. This result illustrated the network formation occurred due to the chemically crosslinking interaction depending upon Maillard reaction [ 35 ]. XPS and FTIR did not find a free –CHO band on OPA in the observable phase in CPNAs, implying that the absolute transformation to C–N and N–C–N bands responded accordingly.…”

Multifunctional Melamine Formaldehyde Composite Foam for High-Temperature Insulation, Flame Retardancy, and Oil–Water Separation

“…MF foam exhibits good flame retardancy performance, but its compressive capacity is poor. Polymers can be added to this foam to obtain a rigid composite foam, thereby enhancing the compression properties of MF. − In addition, MF can also improve the flame retardancy of polymers. One of the ways includes the incorporation of rigid foams in the MF foam to prepare a composite foam.…”