Fig 1

Number of publications on electromagnetic protection foam materials based on supercritical carbon dioxide foaming technology (source: Web of Science)"

Fig 2

(a) Schematic diagram of the supercritical carbon dioxide foaming process; (b) Schematic diagram of the rearrangement of fillers during the foaming process from Ref. [51]. Copyright © 2016, Elsevier; (c) Schematic diagram of electron tunneling among CNTs restrictively distributed in the cell walls from Ref. [54]. Copyright © 2022, American Chemical Society; (d) CNF/PVDF nanocomposite foam model: growth in 1D, 2D , and 3D; (e) Cell wall thickness and nanofiber shortest distance as a function of increased model cell size from Ref. [53]. Copyright © 2022, American Chemical Society; (f) The modeling results showing the morphology of the conductive rod-like filler particle in a complex 3D network at different void fractions, ranging from 0% to 40% from Ref. [57]. Copyright © 2020, Elsevier."

Fig 3

(a) Diagram of electromagnetic shielding mechanism; (b) Schematic illustration of the input impedance of multilayered EMI shielding material with i layers from Ref. [71]. Copyright © 2023, Royal Society of Chemistry; (c) Diagram of electromagnetic shielding mechanism of electromagnetic shielding foam from Ref. [80]. Copyright ©, 2024 The Authors; (d) Schematic illustration of the EM wave absorption mechanisms of PA6/CNT nanocomposite foams from Ref. [81]. Copyright © 2022, Elsevier."

Fig 4

(a) Preparation process of TPU/MWCNTs composite foams and (b) Dissipative process of EMWs in dual-gradient-structured composite foams from Ref. [84]. Copyright © 2025, Wiley-VCH; SEM micrographs of CNF/PVDF nanocomposites [0.03 vol%, (c1) unfoamed solid, (c2) foam 1, (c3) foam 2, and (c4) foam 3] and (d) schematic illustration of biaxial stretching of CNF/PVDF nanocomposite films at different stretching degrees, EMI SE as a function of frequency (X band, 8-12 GHz) of unfoamed (e) and defoamed (f) CNF/PVDF nanocomposites; SET, SEA from Ref. [53]. Copyright © 2022, American Chemical Society; (g) Average specific electromagnetic interference SE values of foam nanocomposites with different PVDF/PE contents from Ref. [86]. Copyright © 2025, Elsevier; EMI (h) SET, SEA, and (i) SER curves in the X-band for asymmetric oriented TCFA composite foam from Ref. [87]. Copyright © 2024, Elsevier."

Fig 5

(a) Preparation schematic of solid PVDF-CNTs and gradient structured PVDF-CNTs foam (b) SEM pictures of gradient-structured PVDF-6-8-10CNTs composite foamed at 8 MPa and 162 °C from Ref. [89]. Copyright © 2024, Springer Nature; (c) Preparation process of PBAT/CNTs composites and foams and Morphology of three-layered foamed samples(d1−d2) F(12−0−12), (d3−d4) F(16−4−16) from Ref. [90]. Copyright © 2024, Elsevier; (e) Scheme of EM wave dissipation mechanism within the composite foams; EMI SE of S-PF/Ni/Ag and F-PF/Ni/Ag composites with different (f−g) Fe3O4@MWCNTs content; EMI SE of the (h) S-PF/Ni/Ag and (i) F-PF/Ni/Ag composites before and after a peeling experiment of 500 times under 100 g weight pressure from Ref. [93]. Copyright © 2024 The Authors."

Fig 6

(a) Schematic illustration of the preparation procedure of PA6/CNT composite foams; (b) RLmin values, (c) matching thickness, and (d) RL-f curves at a different thickness for PA6/CNT nanocomposite foams with a varied cell size under a similar void fractionructure based on scCO2 annealing and foaming from Ref. [99]. Copyright © 2025, Wiley-VCH; (e) Schematic of the preparation process of porous PS50/PMMA50/MWCNT composites with double-percolated structure based on scCO2 annealing and foaming, (f) SEM photos of the PS50/PMMA50/MWCNT composite foams annealed in 20 MPa, 180 °C CO2 and foamed at 20 MPa, 80 °C CO2 with different MWCNT contents, EMI SE versus frequency in 8.2−12.4 GHz for the PS50/PMMA50/MWCNT composites with various MWCNT contents: (g) solid samples annealed in 20 MPa 180 °C CO2, (h) porous samples annealed in 20 MPa, 180 °C CO2 and foamed at 20 MPa from Ref. [100]. Copyright © 2021, Elsevier; (i) Schematic showing interpenetration of RGO/MWCNT and preparation of EP/RGO/MWCNT nanocomposites and (j) EMI SE of foamed EP/RGO nanocomposites from Ref. [103]. Copyright © 2021, Elsevier."

Fig 7

(a) Principle of the gradient foaming process and SEM micrographs of PC and PC nanocomposites saturated during 30 min: (b) PC; (c) PC/1 wt% MWNTs; (d) PC/2 wt% MWNTs from Ref. [105]. Copyright © 2015, Elsevier; (e) Schematic diagram of the EMI-shielding mechanism of double-layer structure for EMI-shielding composite foam, (f) EMI SE, (g) averaged R, A, and T values of the PLA-based foam composites with different mass ratios of CNS in the frequency of 8.2−12.4 GHz from Ref. [106]. Copyright © 2025, Wiley-VCH; (h) Illustrating schematic for the preparation of multi-layered ABS/CNTs foams; (i) Schematic description of EMI shielding mechanism for three-layered ABS/CNTs foams from Ref. [107]. Copyright © 2023, Elsevier."

Table 1

Summary of structural design strategies and key performance metrics of representative polymer-based electromagnetic protection foams."