EMI Shielding Effectiveness and Microwave Properties of E-GR Modified PAA: TiO2-Based Composite at Broadband Including 5G

Abstract

This study proposes a novel composite including: low-cost polyacrylic acid (PAA), TiO2, and varying amounts of expanded graphite (eGR) content for EMI and RFI applications over a broad frequency range of 2.6-30 GHz. The evaluated frequency range is vital for communication, defense, and aerospace applications. With the evolution of 5G and advanced radar systems, the subjective frequencies will continue to shape the future of wireless connectivity and security systems while requiring robust electromagnetic and radio frequency interference (EMI/RFI) management strategies. Based on the following EMI/RFI measurements, the optimum loading percentage of eGR in the polymeric matrix is experimentally determined as 11 wt.%, possessing the desirable qualities of being lightweight, highly corrosion-resistant, cost-effective, and simple to fabricate. Structural characterization was also applied to investigate the as-determined optimum composite structure and interactions of fillers and matrix using a scanning electron microscope, a Fourier transform infrared spectrometer, a Raman spectrometer, X-ray diffraction, and a thermogravimetric analyzer. Total Shielding Efficiency (SEtotal) and permittivity/permeability values are obtained from S-parameter measurements using waveguides in accordance with ASTM D5568 standard. High SE values exceeding 50 dB for 3 mm thickness over 2.6-30 GHz and SE of 11.5 dB/mm were obtained in a waveguide environment. The studied frequency range covers S, C, X, Ku, K, and part of Ka bands, as well as sub-6 GHz/7 GHz (3.3-7.125 GHz), FR3 (7.125-24.25 GHz), and millimeter wave (from 24.25-29.5 GHz for n257, n258, and n261) bands of 5G/advanced 5G systems and networks. A novel metric is proposed as well to assess electromagnetic homogeneity, based on comparing SE(dB/mm) values obtained with CST and measured using a vector network analyzer. The electromagnetic homogeneity of the optimum composite was found to be 97% on average. In a free-space environment, the estimated SE of 46 dB was found to be from the simulation (CST), considering the absence of obstacles or reflections and nearby conductivities or dielectric materials, and the presence of the uniform electromagnetic (EM) field distribution as well as perfect alignment between the source and shielding material. On the other hand, the measured SE of at least 50 dB was reported in a network analyzer environment. The numerical metrics of the SE per mm and the proposed composite's homogeneity percentage significantly contribute to the literature.The numerical metrics for SE (dB/mm), the measured homogeneity percentages, and the performance of the proposed composite together represent a significant contribution to the existing body of literature on EMI shielding materials.