The Aramid-Coating-on-Aramid Strategy toward Strong, Tough, and Foldable Polymer Aerogel Films

Abstract

Aerogel has been much highlighted as an emerging lightweight thermal insulation material, but problems such as fragility, low strength, liquid permeability, and lack of flexibility greatly limit further applications. In this work, a facile aramid-coating-on-aramid (ACoA) method is demonstrated to fabricate all-aramid aerogel composite films for thermal insulation. The method started from the bottom-up synthesis of polymerization-induced para-aramid nanofibers (PANF), which were easily transformed into aerogel films through the vacuum-assisted filtration followed by the freeze-drying techniques. Then, the heterocyclic aramid (HA) solution prepared through the low-temperature-solution polycondensation was used as the coating to be applied onto the PANF aerogel films, and composite films of HA/PANF aerogel were simply achieved with HA contributed to the dense and continuous surface layer. The bulk HA film is of superior mechanical and thermal properties to those of the PANF film. Moreover, reliable interfacial interlocking structures were developed beneath the outermost surface via the interpenetration of the infiltrated HA with PANF network. The comprehensive result was the 15 times enhanced tensile strength, 33 times enhanced fracture toughness, the high thermal decomposition temperature, and the additional flexibility for the foldable films of HA/PANF aerogel. The sealing of the surface macropores greatly suppressed the surface chalking and high water absorption. However, the survival of the tiny pores inside the composite maintained the low enough level of the thermal conductivity to provide effective protections against high temperature not only in air but also under wet or even liquid conditions, suggesting the broader applications for thermal insulation.

Ionic Liquid Directed Spinning of Cellulose Aerogel Fibers with Superb Toughness for Weaved Thermal Insulation and Transient Impact Protection

“…Noteworthily, our cellulose nanoporous aerogel fibers can achieve toughness up to 21.85 MJ/m 3 and tensile strain up to 107%, much outperforming the reported aerogel materials in the literature (fibers or films, Figure k and Table S1). ,,,,,,,− ,,,,− For instance, traditional silica aerogel fibers have a low toughness of only ∼0.003 MJ/m 3 and a fracture strain of ∼3.05% . In contrast, cellulose aerogel fibers exhibit ∼7280 times higher toughness than that of silica aerogel fibers as well as ∼36 times higher fracture strain.…”

Multifunctional Thermally Conductive Composite Films Based on Fungal Tree‐like Heterostructured Silver Nanowires@Boron Nitride Nanosheets and Aramid Nanofibers

“…The advantages of aramid nanofibers (ANF) include lightweight, high specific strength, and good high‐temperature resistance, [52, 53] as well as its ability to maintain outstanding mechanical and electrical insulating properties in situations with both high and low temperature and humidity [54, 55] . However, the intrinsically low λ of ANF impedes its ability to meet the needs of 5G electrical or electronic devices and components that are operated at high temperature [56, 57] .…”

“…[46][47][48] On the other hand, it is challenging to precisely control the optimal morphology of heterostructured AgNWs@BNNS thermally conductive fillers because there is no reported technology for orientation or uniform distribution that can be utilized as guidance. [49][50][51] The advantages of aramid nanofibers (ANF) include lightweight, high specific strength, and good high-temperature resistance, [52,53] as well as its ability to maintain outstanding mechanical and electrical insulating properties in situations with both high and low temperature and humidity. [54,55] However, the intrinsically low λ of ANF impedes its ability to meet the needs of 5G electrical or electronic devices and components that are operated at high temperature.…”

Ambient Drying Route to Aramid Nanofiber Aerogels with High Mechanical Properties for Low-k Dielectrics

“…27,28 Moreover, while significant efforts have been focused on developing mechanically strong aerogels, the porosity and mechanical properties of these aerogels are still difficult to control at a large scale in order to meet the basic requirements for dielectric materials. 29,30 Herein, nanoporous ANF aerogels with a layered structure and tunable porosity were fabricated through a facile ambient drying method. The effects of solvent surface tension, as well as the affinity between polymer skeletons and solvents, on the pore structures of ANF aerogels were systematically investigated.…”

“…However, all these aerogels were based on randomly distributed ANF networks prepared by supercritical drying or freeze-drying. Still, preparing ANF aerogels with high porosity through ambient drying presents a grand challenge. , Moreover, while significant efforts have been focused on developing mechanically strong aerogels, the porosity and mechanical properties of these aerogels are still difficult to control at a large scale in order to meet the basic requirements for dielectric materials. , …”