Upcycling of Used Cotton Cloth to Robust Fire-Resistant Carbon Composite Grids with Excellent EMI Shielding

Abstract

The castoff cotton cloth is used for the preparation of robust carbon composite grids (CCGs) by bonding the warp and fill yarns at their contact point by successive impregnation with a solution of sucrose and phenol formaldehyde (PF) followed by curing and carbonization at 900 °C. The CCGs are characterized by X-ray diffraction (XRD), Raman spectra, X-ray photoelectron spectra (XPS), and scanning electron microscopy (SEM) analysis. The width, thickness, empty grid size, and density of the CCGs are modulated in the ranges of 0.354−0.388, 0.587−0.657, 0.357−0.299 mm, and 0.24−0.55 g•cm −3 , respectively, by the PF solution concentrations in the range of 30−80 vol %. The tensile strength and modulus increase from 0.42 to 2.73 and 18.8 to 111 MPa, respectively, when the PF solution concentration increases from 30 to 80 vol %. The CCGs are fire-resistant and exhibit reflection-dominated EMI shielding. The absorption contribution and total EMI shielding effectiveness increase from 30.1 to 46.9 and 34.8 to 52.4 dB, respectively, when the PF solution concentration increases from 30 to 70 vol %. The multiple internal reflections within the empty grid space, interfiber porosity, and lumen of the carbonized cotton fiber led to attenuation of electromagnetic (EM) waves by both conductive losses due to mobile electrons and dielectric losses due to polarization at the functional groups and the large area of carbon−carbon and carbon−air interfaces. The thin, robust, and large-area CCGs produced can be a candidate for high-performance electromagnetic interference (EMI)-shielding material with excellent fire resistance for the strategic sector.