Antibacterial Finishing Of Cotton Fabric With Nano-Sized Silver

Nowadays, along with the improvement of living standard, peoples' awareness of health and environmental protection has increased. More attention has been paid to the sanitation and health protection compared to the aesthetic value and comfort of the fabric, so fabrics which have antibacterial function get more and more favor. Because of its strong inhibitory and bactericidal effects as well as a broad spectrum of antimicrobial activities, silver nano-particles has been paid great attention. In this paper, silver was used as antibacterial agent to finish cotton fabric.Two different methods were used to endow the cotton fabric with antibacterial activity: synthesis of nano-sized silver colloidal solution, and the application to cotton fabric; cotton fabrics were imparted antibacterial activity by treating with an in-situ method of reducing silver ions in the fabric.In this paper, various factors and process conditions which affect the synthesis of nano-sized silver colloidal solution were discussed. By measuring the average size of silver particles synthesized in different conditions, the preparation method was optimized. Finally a uniformly dispersed silver colloidal solution was obtained and it performed good stability. The particle sizes of the synthesized silver were 15-20nm according to the transmission electron microscopy.Then the nano-sized silver colloidal solution was applied to the antibacterial finishing of cotton fabric. The factors affecting the performance of the finished cotton fabric were analyzed, such as liquor ratio, the ways the fabric dried .The finishing process was optimized by measuring the silver content, whiteness and washing durability of the fabric. The antibacterial activity of the finished cotton fabric was investigated using Gram positive bacteria Staphylococcus aureus (S. aureus).The results showed that cotton fabric finished with nano-sized colloidal silver had a very good performance. After 10 times' washes, the silver content on the fabric could remain above 81%. The inhibition of the colony count of S. aureus was 99.9% when the silver content on the finished cotton fabric was about 62μg·g^-1. Combined with the washing durability of the finishing, it could be said that when the concentration of the colloidal silver was 10mg·L^-1, the finished fabric after 10 times' washes could still have a very good antibacterial activity.A comparison of padding process and impregnating process was made in the process of in situ synthesis of nano-sized silver particles in cotton fabric in two bathes. The results showed that with the same concentration of AgNO₃ solution, the impregnated fabrics had much higher silver content than the padded ones. This was possibly due to the higher fiber accessibility in the impregnating process. In the impregnating process, two different methods were applied on the cotton fabric: drying and steaming, their influence on the fabric was also discussed. Meanwhile the factors which affected the silver content and whiteness of the finished fabric in steaming process such as the time of steaming, the steaming temperature and the humidity were optimized.The results showed that, cotton fabric finished with steaming method could obtain higher silver content than other methods and the whiteness of the finished fabric didn't decrease much. Meanwhile the finished fabric had excellent washing durability, after 10 times' washes, the silver content of the fabric could remain above 93%, even after 50 times' washes, the silver content of the fabric could still remain above 62%.The antibacterial activity of the finished cotton fabric was also investigated using Gram positive bacteria Staphylococcus aureus (S. aureus). The inhibition of the colony count of S. aureus was 99.9% when the silver content of the finished cotton fabric was about 60μg·g^-1(when the concentration of the silver in AgNO₃ solution was 8mg·L^-1).Combined with the washing durability of the finishing, it could be said that when the concentration of the silver in AgNO₃ solution was above 15mg·L^-1, the finished fabric after 50 times' washes could still have a very good antibacterial activity.The application of in situ synthesis of nano-sized silver particles in cotton fabric in one bath was also carried out. Generally, with the same concentration of silver in the finishing solution, the two bathes method was better than one bath method both in considering the silver content and washing durability of the fabric.