Study on the sweat resistance of Ag-plated yarns in simulated wearing

Silver-plated yarn is one of the fundamental materials in smart textiles. However, the plating can be corroded seriously by human sweat during daily wear, degrading the electrical conductivity. To address this issue, this article designed a new set of experimental protocols to faithfully simulate sweat immersion in daily wear. Artificial sweat with pH 5.5 and 8.0 was applied to five types of yarns on a daily basis, and changes in the morphological, electrical and mechanical properties of the yarns before and after treatment were recorded. The results showed increasing resistance of the yarns after exposure to sweat at both pH values. After 10–20 test cycles, almost all samples lost their electrical conductivity, and their mechanical properties also degraded. Yarn service life in acidic sweat was longer than in alkaline sweat. Morphological characterization revealed that the coating on the yarn surface peeled off after treatment. The coating reacted electrochemically with Cl − in sweat, resulting in interruption of the conductive pathway, hence a sudden increase in resistance. Compared to acidic environment, Ag is more prone to undergo redox reaction in alkaline environment. Therefore, silver-plated yarn corrodes faster in alkaline sweat. Finally, the decrease in mechanical properties was due to the swelling behavior of nylon 6 in sweat.