Abstract
Wool has disulphide bonds containing-hydrophobic external keratin layers, which act as a barrier for the modification through coating with hydrophilic materials. For that reason, in this work, to ensure a dense and homogenous conductive polymer coating onto the wool, the fabrics were subjected to the reduction process in the aqueous alkaline medium containing agents that can attack these disulphide bonds. Then, one of the polyaniline derivatives, poly(mtoluidine) (PMT), was coated onto wool by in situ polymerization of m-toluidine sulphate using ammonium persulfate (APS) as an oxidant. The effects of conditions, such as the composition of reduction-bath and types of dopants were investigated, on the mass increase (%) and surface resistivity of the composite. The reduction pretreatment of wool with sodium hydrosulphide significantly improved the coating density, conductivity, and colour shade of PMT on the surface, compared to an untreated one. The coating stability of PMT/wool composite was examined by rubbing test and detergent washing, through surface resistivity measurements. The changes in structural and surface properties of wool fabrics were determined with ATR-FTIR, contact angle, and optical microscopic techniques, respectively. The performance of PMT/wool composite was also examined in the electromagnetic shielding effectiveness (EMSE) measurements within 30 MHz-3 GHz.
Highlights
Wool is one the most preferred natural polymer that has been used as a textile material, due to its unique properties such as keeping warm, having secure maintenance/handling, and biocompatible
The disulphide link of keratin can be converted into oxidized another disulphide form [10,13] or disrupted to give SH groups, through chemical reducing agents that are capable of attacking disulphide links containing S atoms such as mercaptoethanol, L-cysteine, thioglycolic acid (TGA)
To form -SH groups that tend to adsorb cationic substances such as conjugated monomers, and to enable the modification of the surface with chemical methods such as coating, the wool fabrics were subjected to the reduction process in the aqueous alkaline medium containing reducing agents with sulphide atoms [9,11,13,14]
Summary
Wool is one the most preferred natural polymer that has been used as a textile material, due to its unique properties such as keeping warm, having secure maintenance/handling, and biocompatible. The disulphide linkages containing external keratin layers limit the usage of wool for the modification of its surface, such as coating with a hydrophilic chemical. We preferred the use of TGA and NaHS as organic and inorganic reducing agents for the cleavage of disulphides, respectively. The present work aims homogenously and densely modification of the hydrophobic wool surface, by a hydrophilic conductive polymer after the application of a chemical reduction pretreatment. In this study, we used a relatively more cost-effective method and apparatus compared to plasma treatment and employed environmental-friendly chemicals that might have minimal harmful effects on nature such as TGA, NaHS, and urea in the aqueous alkaline media. The prepared composite was examined in the electromagnetic interference (EMI) shielding application in the near field (radio and low microwave) frequency range between 30 MHz–3GHz
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