Antibacterial Finishing Of Cotton Fabric With Nano-sized Silver Colloidal Solution And The Determination Of Silver Content On Fabric

An alarm bell to human health has been made with the crisis of SARS and the threat of avian influenza occurred recent years, therefore it is fairly important to develop the antibacterial finishing of fabric, which can be good media for viruses to reproduce and diffuse. In this paper, nano-sized silver based inorganic material was used as antimicrobial agent to finish cotton fabric.The antibacterial efficacy of nano-sized silver-treated cotton fabric is decided by the silver content. In order to make a study on the relation between antibacterial efficacy and silver content, the silver content on cotton fabric should be determined; however, the standard test method of trace silver on fabric has not been established until now.In this study, Uniform Design was employed to decide the optimized conditions of microwave digestion. Based on the major influence factors and their levels, the experiment was arranged according to the uniform design table of U₁₂（6⁴）. The multiple regression model was obtained by using stepwise multiple regression analysis, and it was used to obtain the optimal combination of factor-values by using Quasi-Newton method and Universal Global Optimization method in the 1stOpt software, and was then validly proved by the validation experiment. The optimized parameters of microwave digestion are that the volume of HNO₃ is 5.0mL, the volume of HCl is 3.4mL, the temperature of digestion is 170℃, and the time of digestion is 8 minutes.Because of no available national reference materials for cotton, the standard samples recovery was used to estimate the reliabilities of the test method by this paper. The recovery ranged between 90.5% and 103.2%. Since the standard samples recovery was not always reliable, the same fabric sample was tested by the test method provided by Oeko-Tex and EPA3052 respectively, and the results were 0.38μg·mL^-1 and 0.56μg·mL^-1, while the results tested under the optimized conditions of this paper was 0.55μg·mL^-1 the results indicated that the test method determined in the study was more accurate than Okeo-Tex method and similar to EPA3052 in testing the content of silver on fabric. The experiments on interference of elements showed that Cu、Zn、Pb、Cd had no influence on the digestion method. While using Flame Atomic Absorption Spectrometry to determine the silver content on cotton fabric, experiments were carried out under the optimal flame program to search the steady peak optical absorption value, and the variation tendency of optical absorption value with the electric current was studied. Results showed the optimal test conditions are that wavelength is 328.1nm, electric current is 3mA, seam width is 1.2nm, burner height is 7.0mm, gas （acetylene） is 45NL·h^-1 and gas/ox. is 0.093.Before antibacterial finishing, the nano-sized silver colloidal solution was pre-treated using the cell ultrasonic wave pulverizer. The analysis of the diameters showed that Z-average diameter increased slightly with the time and reached a steady value gradually, XRD result showed that the silver in the nano-sized silver colloidal solution existed in the form of elementary substance.Since the experiment which is used to develop antibacterial finishing for cotton fabric was of multifactor and multi-level, an optimization was made by uniform design to determine the optimized parameters. The multiple regression model was obtained by using stepwise multiple regression analysis, and it was used to obtain the optimal combination of factor-values by using Quasi-Newton method and Universal Global Optimization method in the 1stOpt software, and was then validly proved by the validation experiment. The determined optimum treatment process is that the fabric is immersed in a nano-silver solution of 11.7μg·mL^-1 at the temperature of 80℃for 30 minutes, padded to give a wet pickup of 75% through squeeze rolls with two dips and two nips, and then dried for 5 minutes at 70℃and cured for 5 minutes at 100℃.The cotton fabric treated under the optimized parameters was digested by microwave, and the tested silver content of the fabric was 42μg·mL^-1. The cotton fabric had an antibacterial efficacy above 99.9% against staphylococcus and coliform bacillus.