In this article we review some of the contemporary antimicrobial agents used in textiles, including quaternary ammonium compounds, N-halamines, chitosan, polybiguanides, triclosan, nanoparticles of noble metals and metal oxides, and bioactive plant-based products. According to their mechanism of antimicrobial activity, toxicity, durability and ecological acceptability, these agents can be divided into biocides and biostats, leaching and bound antimicrobials, controlled-release and barrier-forming agents, and agents of poor and good washing resistance. In view of the need for ecologically friendly antimicrobial finishing, much research has focused on the synthesis of antimicrobial agents where the leaching antimicrobials have been replaced with the bound antimicrobials. The latter have mostly been prepared using polymerizable quaternary ammonium salts with acrylate groups, alkyltrialkoxysilanes with incorporated quaternary ammonium groups, reactive cationic dyes, appropriate crosslinking agents, complexes with cyclodextrines, and encapsulated nanoparticle agents embedded into polymer matrices of various compositions.

In a continuation of previous studies, the wetting properties of the hydrophobic diureapropyltriethoxysilane [bis(aminopropyl)-terminated polydimethylsiloxane (1000)] (PDMSU) sol-gel hybrid, which forms washing-resistant water-repellent finishes on cotton fabrics, were further investigated. The addition of 1H,1H,2H,2H-perfluorooctyltriethoxysilane (PFOTES) to PDMSU resulted in a highly apolar low-energy surface on aluminum with gammaStotal equal to 14.5 mJ/m2 and a DetlaGiwi value of -82 mJ/m2. Mixed PFOTES-PDMSU finishes applied on cotton fabrics increased the water contact angles (thetaw) from approximately 130 degrees (PDMSU) to 147 degrees, also imparting oleophobicity (thetadiiodomethane=130 degrees, thetan-hexadecane=120 degrees) to the finished cotton fabrics. Washing caused breakage of the coating's integrity as established from SEM, which was attributed to the partial removal of PFOTES from the composite films, also shown by subtractive IR attenuated total reflectance (ATR) and XPS spectral measurements made on washed and unwashed fabrics. The antibacterial properties of the PFOTES-PDMSU-finished fabrics were assessed with the transfer method (EN ISO 20743:2007), revealing that the reduction of Escherichia coli bacteria on unwashed cotton fabrics was nearly 100%. Moreover, for washed (10 times) cotton fabrics a much higher bacterial reduction was noted for the PFOTES-PDMSU finishes (60.6+/-10.8%), surpassing PDMSU (30.4+/-6.1%) and commercial fluoroalkoxysilane (FAS) (21.9+/-5.7%) finishes. The structure of PFOTES-PDMSU gels, xerogels, and the corresponding coatings was investigated by analyzing the 29Si NMR and IR ATR spectra and comparing them with the spectra of PFOTES and octameric (T8) PFOTES based polyhedra. The results revealed the tendency of PFOTES to condense in octameric silsesquioxane polyhedra (T8), coexisting in the PDMSU sol-gel network with cyclic tetramers (T4(OH)4) and open cube-like species (T7(OH)3). The presence of -OH-functionalized PFOTES silsesquioxanes, established even in coatings heat-treated at 140 degrees C (15 min), also explained the excellent washing fastness of PFOTES finishes on cotton fabrics. The regenerative nature of the water- and oil-repellent properties of washed PFOTES-PDMSU-finished cotton fabrics was attributed to the surface mobility of the T8 PFOTES based polyhedra, ousted from the coating interior during consecutive washings.

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