Copyright © 2022 Foshan MBRT Nanofiberlabs Technology Co., Ltd All rights reserved.Site Map
This review systematically discusses the working mechanisms, preparation and modification methods, and recent advances in nanofiber nonwovens and sponges for waterproofing, thermal insulation, and electromagnetic (EM) shielding/absorption.
1.1 Waterproof
On the one hand, water droplet is blocked, but water vapor could be permitted by adjusting the pore diameter between nanofibers, On the other hand, the hydrophobicity of nonwoven is also increased by introducing hydrophobic groups on its surface to minimize the surface energy.
1.2 Thermal insulation
Heat transfer in nanofibers is achieved by heat conduction, radiation and convection. Heat conduction efficiency is affected by fiber contact strength and bulk density; radiation scatters and diffracts when the fiber diameter is smaller than the wavelength of thermal radiation, and temperature changes affect thermal radiation; and thermal convection is mainly transferred through the relative motion of air molecules.
1.3 EM shielding/absorption
The external electromagnetic wave interacts with free carriers and undergoes reflection; the electric or magnetic dipole inside the material generates eddy currents and induced currents, which convert the electromagnetic wave into heat to be dissipated; and the remaining electromagnetic wave inside the material undergoes multiple reflections and attenuates the electromagnetic wave.
2.1 Preparation of nanofiber nonwovens and sponges
Prepare spinning solution, electrospinning to prepare nanofiber nonwovens, cut into staple fibers and then dispersed in non-solvent medium, freeze lyophilization to produce nanofiber sponges.
2.2 Design of nanofiber nonwovens and sponges
Pre-spinning modification:
Adding various functional additives to the spinning solution to give the nanofiber special properties;
post-spinning modification:
Post-spinning modification refers to those processes which allow the treatment of Electrospun Nanofbers after the electrospinning, including physical modification and chemical modification.
3.1 Application of waterproof electrospinning
Long-chain alkyl polymers (LAP) were introduced into waterborne polyurethanes (WPU) to endow the nanofiber nonwovens with hydrophobic channels, and environmentally friendly polycarbodiimide (PCD) was used as a cross-linking agent doped into the electrospinning emulsion. The prepared WPU/PCD/LAP nanofiber nonwovens exhibited excellent properties: hydrostatic pressure up to 35.9 kPa and water vapor transmission (WVT) of 4885 g m-2 d-1.
3.2 Application of insulating electrospinning
Hollow SiO2 spheres were prepared using tetraethyl orthosilicate and added to electrospun polyacrylonitrile (PAN) nonwovens, which conferred low thermal conductivity and excellent thermal insulation properties. To prevent moisture from affecting the thermal insulation effect, the nonwoven was functionally improved to exhibit thermal insulation and hydrophobicity; the hollow SiO2 spheres were uniformly embedded in a high-density fiber network to improve thermal stability and prevent nanoparticle stripping.
4.1 Electrospinning technology
Industrial Production of Nanofibers, Uniform Dispersion of Fillers, Precise Control of Morphology;
4.2 Waterproofing
In-Depth Mechanism of Water Flow and Moisture Diffusion Behavior Inside The Nanofiber Structure, Environmental Pollution Hazards, Durability Under Extreme Conditions;
4.3 Heat insulation
Establishment of Evaluation Criteria, on-Demand Dynamic Modulation, Multifunctional Optimization;
4.4 Electromagnetic shielding/absorption
Adaptable Electromagnetic Shielding/Absorption System, Green Electromagnetic Shielding Performance, Intelligent Electromagnetic Shielding/Absorption Scenarios;
Link to paper: https://doi.org/10.1016/j.mtnano.2024.100452
