Ag-treated Cotton Fabric: Antibacterial, Physical, Hydrophobicity, Steady-StateThermal and Mechanical Properties

Silver nanoparticles (Ag-NPs) are extensively used in textile industry to develop a multifunctional fabric for antibacterial, superhydrophobic and conductive performance. In this work, the Ag-NPs suspensions with the average particle sizes of 20, 31, 38 and 40 nm and different concentrations of 50, 100 and 150 ppm were prepared by reduction of AgNO3 . Then, the cotton fabric was padded with Ag-NPs different in size (20, 31, 38 and 40 nm) and concentration, dried and cured at 90 ˚C and 130 ˚C. The weight percent of silver in cotton fabric was determined by inductively coupled plasma (ICP) spectrometry. Infrared (IR) spectroscopy shoed that upon cotton fabric treatment with Ag-NPs, the stretching bands at around 3000 cm-1 were shifted to lower wavenumbers and the absorption intensity of the bands corresponded to cellulose known as the major component of cotton fiber decreased. The water contact angle (WCA) test showed that the treated fabrics with smaller particles exhibited better hydrophobicity somehow WCA increased to 115˚ for the fabric treated with 20 nm-Ag-NPs comparing to 73˚ for the untreated cotton fabric. Thermal comfort properties (thermal conductivities and resistance) were measured and it was found that thermal conductivity (k) increased with the increase of both particle size and silver concentration. The cotton fabric treated with 150 ppm-20 nm-Ag-NPs suspension exhibited the maximum k value of 0.057 W/m.K comparing to the 0.040 W/m.K measured for the untreated fabric. The mechanical properties (elastic modulus and tensile strength) were investigated using a computer controlled constant rate of extension (CRE) test machine. It was observed that the effect of particle size on the mechanical properties was not so pronounced, while the increase of Ag weight percent in the fabric considerably increased the elastic modulus. However, the tensile strength reduced from 292 MPa for the untreated cotton fabric to about 111 MPa for the cotton fabric treated with 150 ppm-Ag-NPs suspension. It was observed that the cotton fabric treated with silver nanoparticles is stiffer than untreated fabric. The antibacterial activity value “A” obtained showed the all samples were meaningfully effective on both Gram-negative and Gram-positive bacteria, however the cotton fabrics with Ag-NPs against Klebsiella pneumoniae as Gram-negative bacteria are more active than against Staphylococcus aureus known as Gram-positive bacteria. In addition, the antibacterial activity slightly decreased with particle size and significanltly increased with increase of Ag concentration somehow the best activity value (A = 3.12) was recorded for the sample treated in 150 ppm-20 nm Ag-NPs suspension on Klebsiella pneumoniae.