Radiofrequency Shielding by Polypyrrole-Coated Nano and Regular Fibrous Mats

Abstract

This work investigates radiofrequency shielding by polypyrrole (PPy)-coated fibrous mats consisting of nano and regular fibers. Radiofrequency shielding protects human beings as well as electronic devices from the harmful effects of radiofrequency waves. The results of this study show that, generally, lowering the fiber diameter of the coated mats increases the reflection but decreases the absorption of radiofrequency radiation in the range of 5 GHz to 8 GHz. Moreover, absorption of higher frequencies is greater than that of lower frequencies, whereas for reflection the opposite trend is observed. The sum of absorption and reflection of radiofrequencies in the range of 5 GHz to 8 GHz by PPy-coated mats is not affected by the fiber diameter of the mats. PPycoated regular poly(acrylonitrile) (PAN) and poly(ethylene terephthalate) (PET) fiber mats with weight per unit area of 16.67 mg/cm 2 provide radiofrequency shielding above 85%. Nanofibrous mats with weight per unit area of nearly 60 times less showed similar radiofrequency shielding effectiveness as regular fiber mats, highlighting the importance of the high specific surface area of nanofibers.

Electromagnetic Shielding and Reflection Loss of Conductive Yarn Incorporated Woven Fabrics at the S and X Radar Bands

“…Vacuum deposition and electroless metal deposition methods are used to coat polymeric fabric surfaces with nano-metals such as nickel on copper plated polyester (PET) and polyamide (PA) ripstop fabric, silver and gold coated polyester fabric, glass fiber, PET fiber braids overwound with tin-plated copper foil and polypyrole (PPy) coated regular poly(acrylonitrile) (PANi) and PET fiber mats. [8][9][10][11] These products mainly ensure electromagnetic shielding or absorbing EM waves from ground sensitive electronic boards. On the other hand, a variety of fillers are also used inside polymeric coatings to be used as shielding materials.…”

“…However, most of the metals have certain limitations such that aluminum based materials present low impact resistance, stainless steel based materials have higher density which makes the structure heavy and rigid, silver based materials require non-corrosive environment, etc. 12 On the other hand, Dijith et al studied screen printing silver line patterns (vertical or horizontal) on the surface of LSCO loaded epoxy composite (having shielding effectiveness (SE) of around 6 dB at X band and around 5 at 15 GHz) in order to achieve high SE, and they reported SE values of around 7 dB for vertical and around 20 dB for horizontal printed samples in the X Radar band (8)(9)(10)(11)(12), and around 7 dB for vertical and 13 dB for horizontal patterns at 15 GHz, respectively. Furthermore, they mentioned that printing a mesh pattern further increased SE, up to 22 dB at 10 GHz and 18 dB at 15 GHz.…”

Comparison of polyelectrolyte and sodium dodecyl benzene sulfonate as dispersants for multiwalled carbon nanotubes on cotton fabrics for electromagnetic interference shielding

“…Electromagnetic interference (EMI) shielding fabrics have drawn more and more attention because electromagnetic (EM) radiation pollution is becoming a serious public health problem, especially for persons exposed to EM fields for a long time or those sensitive to EM radiation, such as pregnant women and young children, with the widespread use of cell phones, computers, and other electronic apparatuses, such as microwave ovens, TV sets, and refrigerators. To shield EM radiation, various metals, ferrites, and conductive polymers, including copper, silver, stainless steel, carbonyl iron, polypyrrole, and polyaniline, have been used in fabrics to obtain high EMI shielding efficiencies (SEs). Nevertheless, when either metal or conducting polymers are used, the EM power is most likely realized by a reflection mechanism, and this, consequently, causes secondary radiation in the environment.…”