ABSTRACT
Minimizing the impact of electromagnetic radiation (EMR) holds paramount importance in safeguarding individuals who frequently utilize electrical and electronic devices. Electrically conductive textiles, which possess specialized EMR shielding features, present a promising solution to mitigate the risks related to EMR. Furthermore, these textile-based shielding materials could find application as radar-absorbing materials in stealth technology, emphasizing the need for substantial absorption capabilities in shielding mechanisms. In this study, various textile-based materials with an electrically conductive coating that contain the conjugated polymer system poly(3,4-ethylene-dioxythiophene)-polystyrene sulfonate (PEDOT:PSS) were prepared and investigated. The influence of the textile substrate structural parameters, coating deposit, and coating method on their microwave properties-transmission, reflection, and absorption-was investigated. Reflection and transmission measurements were conducted within a frequency range of 2 to 18 GHz. These measurements revealed that, for the tested samples, the shielding properties are determined by the combined effect of reflection and absorption. However, the role of these two parameters varies across the tested frequency range. It was defined that for fabrics coated on one side, better reflection reduction is obtained when the shielding effectiveness (SE) is below |20| dB. It was found that by controlling the coating deposition on the fabric, it is possible to fine-tune the electrical properties to a certain extent, thereby influencing the microwave properties of the coated fabrics. The studies of prepared samples have shown that reflection and transmission parameters depend not only on the type and quantity of conductive paste applied to the fabric but also on the fabric's construction parameters and the coating technique used. It was found that the denser the substrate used for coating, the more conductive paste solidifies on the surface, forming a thicker coat on the top. For conductive fabrics with the same substrate to achieve a particular SE value using the knife-over-roll coating technology, the required coating deposit amount is considerably lower as compared with the deposit necessary in the case of screen printing: for the knife-over-roll-coated sample to reach SE 15 dB, the required deposit is approximately 14 g/m2; meanwhile, for a sample coated via screen printing, this amount rises to 23 g/m2.
ABSTRACT
The way to improve the properties (resistance to washing, delamination, and rubbing off) of the PEDOT:PSS coating applied on wool fabric without reduction of its electrical conductivity by introducing a commercially available combination of low formaldehyde content melamine resins into the printing paste is presented in this paper. Primarily, to improve the hydrophilicity and dyeability of wool fabric, the samples were modified using low-pressure nitrogen (N2) gas plasma. Two commercially available PEDOT:PSS dispersions were used to treat wool fabric by the exhaust dyeing and screen printing methods, respectively. Spectrophotometric measurements of the color difference (ΔE*ab) and visual evaluation of woolen fabric dyed and printed with PEDOT:PSS in different shades of the blue color showed that the sample modified with N2 plasma obtained a more intense color compared to the unmodified one. SEM was used to examine the surface morphology and a cross-sectional view of wool fabric that had undergone various modifications. SEM image shows that the dye penetrates deeper into the wool fabric after plasma modification using dyeing and coating methods with a PEDOT:PSS polymer. In addition, with a Tubicoat fixing agent, HT coating looks more homogeneous and uniform. The chemical structure spectra of wool fabrics coated with PEDOT:PSS were investigated using FTIR-ATR characterization. The influence of melamine formaldehyde resins on the electrical properties, resistance to washing, and mechanical effects of PEDOT:PSS treated wool fabric was also evaluated. The resistivity measurement of the samples containing melamine-formaldehyde resins as an additive did not show a significant decrease in electrical conductivity, while the electrical conductivity was maintained after the washing and rubbing test as well. The best results of electrical conductivity for investigated wool fabrics before and after washing and mechanical action were determined for samples subjected to the combined processing-surface modification by low-pressure N2 plasma, dyeing by exhaust with PEDOT:PSS, and coating by the screen-printing method of PEDOT:PSS and a 3 wt.% melamine formaldehyde resins mixture.