Preparation and Characterization of Nylon 6 / Silver Nanocomposite Fibers for Permanent Antibacterial Effect

The nylon 6/silver nano composite fibers were prepared for the attainment of permanent antibacterial activity to common synthetic textile. The fibers prepared by melt spinning and nylon 6/ Silver nanocomposite were prepared by a modular twin screw extruder.. The antibacterial activities of nano silver in fibers were calculated by percent reduction of two kinds of bacteria staphylococcus aurous and klebsiela peneumoniae. Scanning electron microscopy (SEM) was carried out to observe particle distribution on the nanocomposite fibers. All the nanocomposite fibers were characterized by instron machine.


INTRODUCTION
Textiles have long been recognized as media to support the growth of microorganisms such as bacteria and fungi.] In recent years antibacterial agents that have been used industrially have included quarternary an ammonium salts, metal salt solution, and antibiotics. U][5][6] Nanotechnology has real commercial potential for the textile industry.This is mainly due to the fact that conventional methods used to impart different properties to fabrics often do not lead to permanent effects, and will lose their functions after laundering or wearing.Nanotechnology also can provide high durability for fabrics, because nano-particles have a large surface area-to-volume ratio and high Surface energy, thus presenting better affinity for fabrics and leading to an increase in durability of the function.In addition, a coating of nano-particles on fabrics will not affect their breathability or hand feel. 7For imparting anti-bacterial properties, nanosized silver, [8][9][10][11][12] titanium dioxide [13][14][15] and zinc oxides are used.Metallic ions and metallic compounds display a certain degree of sterilizing effect. 16 contrast, silver, is a non-toxic non tolerant disinfectant that can reduce many bacterial infections significantly.4][5][6] Silver nanoparticles have the properties of a high surface area, very small size, and high dispersion.Several studies have been undertaken to explain the antibacterial properties of Ag ions toward bacteria. Nanocomposite fibers have attracted attention in recent years because improved mechanical, thermal, solvent resistance ad fire retardant properties compare to the pure or conventional composite fibers. The common technique to produce nanocomposite fibers is by melt compounding, which is the easiest and most cost effective method to produce nanocomposites materials. 21lon 6 is one of the most widely used synthetic fibers in textile industry.Besides, nylon 6 is well applicable for various fields, for example, carpet, sock, clothes, film and so on.Then the products made up of nylon 6 need antibacterial activity, one of the important functionalities, than the others.
In this study we prepared nylon/silver fiber using various concentration of Ag nano particles by melt spinning and compared their antibacterial efficacy.The structure and mechanical properties of nanocomposite fibers were analyzed by using Scanning electron microscopy(SEM) and Tensile testing measurement.andcompared their antibacterial efficacy.

Materials and methods
The Ag nanopowder were supplied by Lotus Ltd.Tehran (Iran) and nylon 6 chips were provided Alyaf Iran Co. Tehran, Iran.
All the materials were dried at 120ºC in vacuo for at least 12h to minimize the effect of moisture before being used.Nylon 6/Silver nanocomposite were prepared by a modular twin screw extruder.The temperatures of heating zones from hopper to die were set to 240, 255, 255, and 240ºC, respectively, and screw speed was fixed at 50 rpm.Melt spinning of the nanocomposite fibers was carried out using a single extruder with a capillary die of diameter 5mm and an L/D ratio of 25.During the spinning process, the winding speed of the composite fiber was controlled at 2000 m/min with screw revolution speeds of 15 rpm respectively.The nanocomposite fiber composition and sample codes are shown in Table 1.
The morphologies and sizes of the Ag nano particles were investigated by transmission electron microscopy (TEM).We used the AATCC-100 test method (antibacterial activity assessment of textile materials) to study the antibacterial properties of fabric finished with the nanoantibacterial agents.The fabrics were placed on a germ-containing agar plate and were inoculated with Gram-positive (staphylococcus aureus, ATCC 6538) and Gram negative (Klebsiella pneumoniaei ATCC 4352) bacteria.Specimens corresponding to untreated controls of the same material were placed in intimate contact with the nutrient agar, which previously had been streaked with inoculums of the test bacterium.After incubation for 24h, we evaluated the antibacterial properties of both the untreated fabric and the treated fabrics.

Percent reduction of bacteria (
The number of bacteria on the untreated fabric after 24h; B) The number of bacteria on the antibacterial treated fabric after 24h.
The morphologies of the nanocomposite fibers samples were observed with a Scanning Electron Microscope (SEM) and elemental analysis was conducted with EDAX spectra.We used a sputter coater to precoat conductive gold onto the surface before measuring the microstructures.Table 2 shows the antibacterial properties of nanocomposite fibers had excellent antibacterial effect on all specimens against S aureus and Klebsiella pneumoniaei.It can be seen that the wool fabrics treated with colloidal nano silver had  Mechanical properties of nylon fiber and nanocomposite fibers with1, 1.2 and 1.5% of silver nano particles was shown in table 3.

CONCLUSIONS
This study has shown the antibacterial efficiency was ever 99.5% after 10 washing time.SEM images shown the nanoparticles were well dispersed on samples.The results were obtained for the surface of samples shown that the percent of nanoparticles on the surface of samples with increase concentration of Ag nano particle.

Fig 1 .
Fig 1. Showed the TEM image of the Ag nanoparticles,the diameter of nanoparticles was estimated at 6nm-8 nm.