Characterization of antibacterial silver nanocluster/silica composite coating on high performance Kevlar® textile

High performance textiles such as Kevlar® find large use in many applications including aerospace field, thus require antimicrobial characteristics to avoid the risk of microbial contamination on board of spacecraft and orbital station during prolonged space exploration missions. In this study, Kevlar® fabric has been coated with antibacterial silver nanocluster/silica composite layer with different thicknesses, by means of radio frequency co-sputtering technique. The fibers morphology and composition has been analyzed by means of field emission scanning election microscopy (FESEM), energy dispersion spectrometry (EDS), x-ray photoelectron spectroscopy (XPS). Thermal properties have been evaluated through thermogravimetric experiments (TGA) and differential scanning calorimetry (DSC). The fibers result homogenously coated with the antibacterial layer composed of silica matrix embedding silver nanoclusters. A controlled and gradual release of silver was observed in silver leaching tests in water and artificial sweat. The antimicrobial behavior is verified through inhibition halo and broth dilution tests against different bacterial and fungal species. The in vitro skin penetration test shows that the Ag amount absorbed through the skin is mainly stored in epidermis. Tensile and tear properties were maintained and not degraded by the coating deposition. The reduction of perforation resistance after coating deposition could be considered negligible whereas abrasion test demonstrated an increased resistance of coated sample.