Effect of coating and testing conditions on the antibacterial efficacy of polypyrrole-treated fabrics

In this research work, cotton and polyamide 6,6 fabrics were coated with polypyrrole, an intrinsically electro-conductive polymer that showed antibacterial actions. The study first aims to measure the antibacterial efficacy of polypyrrole-coated fabrics at increasing pyrrole concentrations (2, 4, and 6 g/L) and consider contact times shorter than the standard 60 min between the fabrics and the bacteria. The results showed not trivial antibacterial performances obtained at different conditions on fabrics with hydrophilic (e.g., cotton) and hydrophobic (e.g., polyamide 6,6) characteristics, also evidencing the importance of polypyrrole particle distribution in the fabric. For instance, outstanding performances were revealed by both cotton and polyamide coated with 2 g/L in 30 min against the two tested bacterial strains, Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative). These findings will be valuable for choosing materials and processing conditions when a rapid and solid biocidal effect is needed. Additionally, from the evaluation of electrical features and photothermal activity, it was found that the electrical conductivity, like the antibacterial properties, was strongly affected by the polypyrrole de-doping consequent to washing, in contrast to photothermal features (particularly triggered by infrared radiation), that were not straightforwardly influenced by doping state and did not exert positive effects on the antibacterial properties.