High electromagnetic interference shielding effectiveness achieved by multiple internal reflection and absorption in polybenzoxazine/graphene foams

Abstract

Electromagnetic interference (EMI) is an increasingly severe issue in modern life and high‐performance EMI shielding materials are in desperate need. To achieve high EMI shielding effectiveness (EMI SE), a series of polybenzoxazine/graphene composites foams are developed using a simple sol–gel method. When the graphene loading increases from 1 to 20 wt%, the density of the composites foams drops from 0.4143 g/cm3 to 0.1654 g/cm3. Meanwhile, an electrically conductive path is formed at around 7 wt% of graphene. Below the percolation threshold, the dielectric constant increases with graphene content and composite foam with 5 wt% graphene shows dielectric constant of 10.8 (1 MHz). At the highest graphene content of 20 wt%, the electric conductivity reaches 0.02 S/cm, 10 orders of magnitude higher than pure polybenzoxazine foam. Benefiting from the high electrical conductivity and lightweight porous structure, the composite foam PF/20G delivers an EMI SE of 85 dB and a specific SE of 513.9 dB·cm3/g. Importantly, the EMI shielding is dominated by absorption attenuation, with PF/20G shows absorption ratio higher than 98% in the range of 8.4–11.0 GHz, which is believed to be caused by multiple internal reflection and absorption inside the conductive foam.

Sustainable Strategies for Fully Biobased Polybenzoxazine Composites from Trifunctional Thymol and Biocarbons: Advancements in High-Dielectric and Antibacterial Corrosion Implementations

“…33 Numerous research studies have underscored the advantageous molecular flexibility of benzoxazines and their inherent polar functional properties, which enable effective blending and compatibility with various carbon fillers as well as other organic polymers. 34,35 Thus, developing multifunctional biophenol for the preparation of polybenzoxazine matrices have emerged as a pioneering solution with transformative potential. 36 In response to this imperative, an attempt has been made to develop multifunctional, fully biobased polybenzoxazines derived from biothymol, utilizing five different natural amine sources.…”

Comprehensive review on polymer composites as electromagnetic interference shielding materials

“…Electromagnetic interference shielding materials must have good electrical conductivity and low magnetic permeability so that the permeation of EM waves is low. [4][5][6] Although metals like steel, copper and aluminum are suitable for EMI shielding; higher density, corrosion, oxidation, high forming and material cost restrict the use of these materials in outdoor shielding applications. Innovative electronic systems apart from effective EM shielding demand properties such as ease of manufacturing, flexibility in material design, low thermal expansion coefficient, non-corrosiveness.…”

A study to determine electromagnetic interference‐shielding effectiveness on bio‐based polyurethane foam reinforced with PVDF/MgO/Ni for emerging applications

“…In the X‐band (8–12 GHz), the shielding effectiveness (SE) of popular commercial applications is roughly 20 dB 2 . EMI shielding is the process of shielding EM waves using a shield made up of conductive or magnetic materials 3,4 …”

“…2 EMI shielding is the process of shielding EM waves using a shield made up of conductive or magnetic materials. 3,4 Nanoparticles-induced PU foam can be used as shielding material instead of metal sheets because metal sheets have more weight and are not flexible. And researchers are trying to develop composites of nanoparticles as an alternative to metal sheets.…”