The aim of this work was to investigate the antimicrobial activity of knitted fabric intended for medical purposes as well as the influence of antimicrobial treatment on the compression work, volume resistivity, water sorption. and water retention of the examined material. Polyamide/elastane plain jersey knitted fabric was treated with a polymer matrix of chitosan gel in which either gentamicin sulfate or autochthonous essential oil of Picea abies was incorporated as an active substance. The treated fabrics showed a wide range of antimicrobial activity on microorganisms ( Staphilococcus aureus, Escherichia coli, Klebsiella and Candida albicans ) and therefore may have various medical applications. However, antimicrobial treatment changed the mechanical and physical-hygienic properties of the knitted fabric. The antimicrobial coatings decreased the total, elastic and irreversible compression work, water sorption, and volume resistivity, and increased the water retention of the fabrics. Antimicrobial treatment with chitosan and gentamicin sulfate produced a knitted fabric with good antimicrobial properties. However, if good mechanical and physical-hygienic properties are required, antimicrobial treatment with chitosan and essential oil of Picea abies has the advantage over treatment with gentamicin sulfate.
In this work, the volume electrical resistivity and dielectric loss tangent of viscose/polypropylene multipurpose nonwoven fabrics were examined. According to the obtained results, the changes in the volume electrical resistivity depend on the applied chemical bonding agent, viscose fiber content, moisture content, fabric thickness, fabric weight, and relative air humidity. Based on the volume electrical resistivity hysteresis, the portion of sorbed moisture retained in the material after desorption, as well as the portion of moisture removed from the material during desorption, were determined. Furthermore, the dielectric loss tangent measured at the frequency range between 30 Hz and 140 kHz, for the samples exposed to different relative air humidity (40 % and 80 %) and wet samples, is dependent on the chemical bonding agent, viscose fiber content, moisture content, as well as frequency of the external electric field. The dielectric loss tangent measured at 80 % relative air humidity showed a peak at about 100 Hz, while for the wet samples, the peak was observed in the frequency range between 30 and 140 kHz. In a wet state, the dielectric loss tangent is primarily influenced by the water molecules present in the sample.
In this paper, the preparation of the antimicrobial silver loaded hemp fibers were carried out by selective TEMPO-mediated oxidation, i.e. oxidation with sodium hypochlorite and catalytic amount of sodium bromide and 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO), followed by silver sorption from aqueous silver nitrate solution. The most suitable experimental conditions for the selective TEMPO-mediated oxidation were determined by changing oxidation conditions: concentration of sodium hypochlorite and duration of sorption. The obtained results showed that the maximum sorption capacity (0.703 mmol of silver per gram of fibers) of modified hemp fibers was obtained for the sample modified with 9.67 mmol NaClO per gram of fibers, during 4 hours. SEM microphotographs of the modified hemp fibers with incorporated silver showed uniformly distributed silver particles on the surface of fibers, with isometric shapes and sizes from 10 to 100 nm, despite the fact that silver was sorbed from ionic solution. The antibacterial activity of the TEMPO-oxidized hemp fibers with silver particles was confirmed in vitro against two strains: Staphylococcus aureus (ATCC 25923) and Escherichia coli (ATCC 25922), and the antifungal activity against fungi Candida albicans (ATCC 24433). The best antimicrobial activity of silver-loaded TEMPO-oxidized hemp fibers was showed against strain Staphylococcus aureus. [Projekat Ministarstva nauke Republike Srbije, br. Acknowledgments. This study has been supported by Ministry of Education, Science and Technological Development of the Republic of Serbia, br. OI 172029
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