Firefighting protective clothing is an essential equipment for firefighters that can provide protection from all kinds of thermal hazards and prevent burn injuries. However, it is still a challenge to develop lightweight firefighting clothing without compromising their excellent fire-resistant and thermal-protective performance. In this study, we report a novel polyimide aerogel fiber-based double-layer smart textile comprising of flame-retardant outer layer (ambient-side) with excellent fire resistance and phase-changeable inner layer (next to skin side) with thermal-regulating function, achieving comprehensive flame-retardant and thermal-protective function. The polyimide-hydroxyapatite-reduced graphene oxide (PI-HAP-rGO) aerogel fabric (outer layer) acquires 54.7% and 70.0% reduction of peak heat release rate compared with that of pure PI aerogel fabric and commercial aramid fabric, respectively, exhibiting excellent fire resistance. The phase-changeable polyimide-hydroxyapatite/eicosane (PI-HAP/C20) fabric (inner layer) with high melting enthalpy of 193.2 J g −1 can delay the temperature rise by thermal buffering effects during the phase change process, endowing cool somatosensory temperature for firefighters. Consequently, the double-layer smart textile can extend the time (280.0 s) to pain threshold of human skin, much longer than that of the commercial aramid fabric (101.0 s) and glass fiber fabric (56.5 s), which exhibits huge potential for next-generation firefighting clothing. A novel polyimide aerogel fiber-based double-layer smart textile comprising of flame-retardant outer layer and phase-changeable inner layer exhibited outstanding flame-retardant and thermal-protective performance, demonstrating great potential for next-generation firefighting clothing. • The smart textile comprising of PI-HAP-rGO aerogel fabric as the outer layer and PI-HAP/C20 fabric as the inner layer was fabricated. • PI-HAP-rGO aerogel fabric exhibits efficient fire resistance with the limited oxygen index value (LOI) up to 47.5%. • There exists 70.0% reduction of PHRR for PI-HAP-rGO aerogel fabric compared with that of commercial aramid fabric. • PI-HAP/C20 fabric has excellent thermal management with high melting enthalpy (193.2 J g −1 ). • The smart textile could delay around 280.0 s to reach pain threshold in the high temperature environment. 

Flame-retardant and thermal-protective polyimide-hydroxyapatite aerogel fiber-based composite textile for firefighting clothing

Ultralight aerogel textiles based on aramid nanofibers composites with excellent thermal insulation and electromagnetic shielding properties

Aerogel fibers inherit the merits of aerogel and fibrous materials, such as high porosity and satisfactory knittability, demonstrating great potential as thermal protective materials applied in harsh environments. Nevertheless, the inferior mechanical property resulting from the porous structure immensely hampers the practical application of aerogel fibers. Herein, we develop robust and thermally insulating long polyimide fiber-reinforced polyimide composite aerogel fibers (LPF-PAFs). The porous crosslinked polyimide aerogel as the sheath endows LPF-PAFs with good thermal insulation performance, while the long polyimide fibers as the core provide LPF-PAFs with superior mechanical strength. Due to the introduction of the high-strength long polyimide fibers to undertake significant stress, LPF-PAFs display outstanding strength surpassing 150 MPa without obvious mechanical performance degeneration in a wide range of temperatures from -100 to 300 °C. Moreover, the textile woven by LPF-PAFs exhibits a superior thermal insulation ability and stability to cotton textile at 200 and -100 °C, indicating its potential application in thermal protective clothing under extreme environments.

Mechanically Strong and Thermally Insulating Polyimide Aerogel Fibers Reinforced by Prefabricated Long Polyimide Fibers.

Pharmaceuticals, especially amine-based pharmaceuticals, such as nizatidine and ranitidine, contaminate water and resist water treatment. Here, different amounts of graphene sheets are coupled with g-C3N4 nanosheets (wt% ratio of 0.5, 1, 3 and 5 wt% of graphene) to verify the effect of surface plasmon resonance introduced to the g-C3N4 material. The synthesized materials were systematically examined by advanced analytical techniques. The prepared photocatalysts were used for the degradation of amine-based pharmaceuticals (nizatidine and ranitidine). The results show that by introducing only 3 wt% graphene to g-C3N4, the absorption ability in the visible and near-infrared regions dramatically enhanced. The absorption in the visible range was 50 times higher when compared to the pure sample. These absorption features suggest that the surfaces of the carbon nitride sheet are covered by the graphene nanosheet, which would effectively apply the LSPR properties for catalytic determinations. The enhancement in visible light absorption in the composite was confirmed by PL analysis, which showed greater inhibition of the electron-hole recombination process. The XRD showed a decrease in the (002) plan due to the presence of graphene, which prevents further stacking of carbon nitride layers. Accordingly, the Gr/g-C3N4 composite samples exhibited an enhancement in the photocatalytic performance, specifically for the 5% Gr/g-C3N4 sample, and close to 85% degradation was achieved within 20 min under solar irradiation. Therefore, applying the Gr/g-C3N4 for the degradation of a pharmaceutical can be taken into consideration as an alternative method for the removal of such pollutants during the water treatment process. This enhancement can be attributed to surface plasmon resonance-induced photocatalysis in a 2D/2D graphene/g-C3N4 heterostructure.

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Surface Plasmon Resonance Induced Photocatalysis in 2D/2D Graphene/g-C3N4 Heterostructure for Enhanced Degradation of Amine-Based Pharmaceuticals under Solar Light Illumination

Polymeric aerogels with low dielectric constant (low-k) are an important material solution for applications in high-frequency terminal electronic devices. However, most aerogels are prepared using high-cost supercritical drying or freeze-drying methods and typically exhibit poor mechanical properties and low thermal stability, which limits their use in practical applications. Here, we report the fabrication of aerogels with layered structure and hierarchical nanopores based on aramid nanofibers (ANFs), using a vacuum-assisted filtration method followed by low-cost ambient drying. The porosity of the ANF aerogels can be controlled from 38 to 79% by rationally selecting solvents with different surface tension for solvent exchange, tuning the affinity between solvents and ANF skeletons as well as controlling the solvent evaporation rate during the ambient drying process. The ANF aerogels have an ultralow and tunable dielectric constant as low as 1.56 while exhibiting a low dielectric loss between 0.0040 to 0.0055 at 1 MHz. The advantageous low-k property can be preserved at high temperatures up to 300 °C, and an inherent flame retardancy is achieved due to the rigid and all-aromatic backbone structure of poly(p-phenylene terephthalamide). Moreover, the nanoporous ANF layers with relatively lower porosity compared with the overall porosity of the aerogel provide strong mechanical strength and modulus, while the presence of larger nanopores from the interspacing of ANF layers ensures a high porosity for the entire aerogel, which endows the aerogel film with superior tensile strength and modulus compared with their conventional counterparts containing homogeneous porous structures. Collectively, these ANF aerogels exhibit low-k, outstanding mechanical properties, high thermal stability, and inherent flame retardancy, enabling them to become very promising next-generation dielectric materials. 

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

Controllable Strong and Ultralight Aramid Nanofiber-Based Aerogel Fibers for Thermal Insulation Applications

Aerogels were listed among the top ten emerging technologies in chemistry by IUPAC in 2022. Their record-breaking properties sparked the emergence of a thriving insulation market, but solutions are sought to promote additional applications. A 3D assembly process based on direct ink writing of “aerogel-in-aerogel” nanocomposites is presented. The printed polyimide-silica aerogels are non-brittle (E = 6.7 MPa) with a super-insulating thermal conductivity (20.3 mW m−1 K−1) and high thermal stability (T5wt% 447 °C). In addition, they display excellent low-loss dielectric properties and microwave transmission over all relevant communication bands and can be functionalized for electromagnetic interference (EMI) shielding. The high shape-fidelity printing, combined with laser-induced etching of thermally conductive graphene layers, enable precise thermal management for portable electronics or maintain an extreme temperature gradient (−40 to +50°C) across a millimeter-scale partition. 

https://onlinelibrary.wiley.com/doi/pdfdirect/10.1002/admt.202202155

Mengmeng Li

Papers

Controllable Strong and Ultralight Aramid Nanofiber-Based Aerogel Fibers for Thermal Insulation Applications

Ultralight aerogel textiles based on aramid nanofibers composites with excellent thermal insulation and electromagnetic shielding properties

3D Printed Polyimide Nanocomposite Aerogels for Electromagnetic Interference Shielding and Thermal Management