Abstract
Abstract In this study, we have produced a lightweight foam composite material by a simple freeze-drying method, which is composed of carboxylated multi-walled carbon nanotubes (MWCNTs), mesoporous carbon hollow microspheres (MCHMs), water-based polyurethane (WPU), and polyvinyl alcohol (PVA). MCHMs were prepared by a novel and facile method. We found that the electromagnetic shielding performance of foam composites can be adjusted by adjusting the density of foam composites, and the electromagnetic shielding performance of composites can be enhanced through the synergistic effect of hollow mesoporous carbon and MWCNTs. The composite material with a density of 232.8042 mg·cm−3 and 40 wt% MWCNT has a δ of 30.2 S·m−1 and SE of 23 dB. After adding 10 wt% MCHMs to the composite material, δ reaches 33.2 S·m−1, and SE reaches 28 dB. Both absorption losses accounted for 70%. The increase in the content of MWCNT, the increase in density, and the introduction of MCHMs all have a positive effect on the δ and SE of the composite material.
Highlights
With the rapid growth of a new generation of industries such as aviation, aerospace, and automobiles, miniaturized electronic products are developing rapidly, which brings the problem of electromagnetic radiation, whichThis work is licensed under the Creative Commons Attribution 4.0224 Shaofeng Liang et al.so they are very suitable for blending with water-based polyurethane (WPU) and polyvinyl alcohol (PVA) [21,22,23]
After WPU and PVA are mixed with water to form a gel, the water in the system is removed by freeze-drying technology to form a foaming material
Concentrated ammonia aqueous solution (NH3·H2O, 25%), hydrofluoric acid (HF, 25%), resorcinol formaldehyde (37%), tetraethyl orthosilicate (TEOS), multi-walled carbon nanotubes (MWCNTs), polyethylene glycol (PEG, Mn = 400), 2-hydroxy-2-methylpropiophenone, isophorone diisocyanate (IPDI), hydroxyethyl acrylate (HEA), 2,2-dimethylolpropionic acid (DMPA, vacuum dried at 90°C before use), triethylamine, 2,6-di-tert-butyl p-cresol, 1,4-butanediol (BDO, 99%), dibutyltin dilaurate (99%), 2-hydroxy-1-[4-(2-hydroxyethyl)phenyl]-2-methyl1-propiophenone (Irgacure 2959, 95%), acetone (Ac), PVA (Mn = 600), and absolute ethanol (EtOH) were of analytical grade
Summary
With the rapid growth of a new generation of industries such as aviation, aerospace, and automobiles, miniaturized electronic products are developing rapidly, which brings the problem of electromagnetic radiation, which. They are very suitable for blending with WPU and PVA [21,22,23]. There are many methods for preparing foamed materials, such as the supercritical fluid foaming method [24,25], melt mixing method, extrusion method [26,27], phase separation method [28,29], aerogel preparation technology [30,31], and so on. After WPU and PVA are mixed with water to form a gel, the water in the system is removed by freeze-drying technology to form a foaming material. This method is environmentally friendly and low in cost. By controlling the moisture content, the density of the foam material can be controlled, so it is suitable for large-scale applications
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