An evaluation of the relationship between application method, concentration, and antimicrobial efficacy of an antimicrobial finish after accelerated laundering

This study addresses the need for an effective and durable antimicrobial finish for performance textiles using silver (Ag) as the antimicrobial agent on plain-weave nylon fabric. Three different concentrations of AgCl + TiO2 (500ppm, 2500ppm, and 5000ppm) were applied using pad and exhaust application methods. Exhaust bath samples were taken at 0, 15, 30, 45, and 60 minute time points. Ag concentration analysis provided insight on exhaustion behavior. Samples from each treatment group underwent 0, 1, 5, and 10 accelerated laundering cycles and were tested against Escherichia coli and Staphyloccocus aureus. Exhaustion in all three fabric bath concentrations occurred rapidly in the first 15 minutes, continuing to exhaust at a slower rate throughout the sample time frame. Samples treated with the exhaust application method produced larger zones of inhibition and retained antimicrobial effectiveness through more launderings than those treated with the pad application against both bacterial species. All fabric samples lost antimicrobial effectiveness after 5 accelerated launderings, well below the industry standard of 50. A statistically significant difference in the mean zones of inhibition existed between pad and exhaust application methods after 0 wash cycles for E. coli. After 0 accelerated laundering cycles, S. aureus exhibited a mean zone of inhibition on the statistical cusp of significance between application methods. A statistically significant difference existed in the mean zones of inhibition between Ag concentrations after 0 accelerated laundering cycles for both bacterial species. While results of this experimentation show Ag does exhaust onto nylon fabric, a bath treatment or alteration in exhaustion conditions, such as addition of a binding agent, may yield complete exhaustion, leaving minimal Ag in wastewater. While the exhaust application method provides greater antimicrobial action at low washings than the pad method, it does not improve the longevity of antimicrobial properties after extended washing. Addition of an auxiliary to the exhaustion bath could improve durability to laundering, reducing Ag in wash effluent, and perhaps cost effectiveness of treatment. This study provides future researchers with a foundation for research that focuses on improving the exhaust application method