Antibacterial Functional Finishing Of Silk Fabric

Silk fiber is a kind of natural protein fiber which People love to use for its appearance and feel.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,so silk fabrics which have antibacterial function get more and more favor.Because of its strong inhibitory and bactericidal effects in vary low concentration.A series of silver inorganic antimicrobial agent have been paid great attention in resent years.In this experiment,silver was used as antibacterial agent.In this paper,silk fabrics were imparted antibacterial activity by treating with an in-situ method of reducing silver ions in the fabric.Silver nitrate was used as the pre-agent,and right kind of reducing agents were chosen.As the method of measuring the silver content on silk fabric hasn’t established,research work has done in this experiment.Then the acid and appropriate process was chosen to digest silk fabric.A stable and accurate result of silver content on silk was obtained when silk was digested by HNO₃+H₂O₂+HCl.After optimizing the parameter of AAS Zeenit 700 by the function of "Automatic flame optimization",we got the best testing elements as following:HCL current is 3.0mA,Slit width is 1.2nm,Burner height is 6mm,fuel is 501/h,Gas/Ox is 0.096.The content of silver on silk fabric got by using the optimized testing elements of AAS Zeenit 700 were at a small degree of discrete and more stable by the proof of Parallel experiments.Reagent B was chosen to reduce the AgNO₃.Compared with reducing agent A,reagent B is a more environment-friendly agent.The finishing process conditions of silk was optimized by orthogonal experiment,which increased the silver content on fabric and did a slight harm to the whiteness and feeling of the fabric.Washing durability of the fabric was tested by measuring the silver content on silk fabric before and after washing.When the silver concentration of the AgNO₃ solution was about 2ppm,the silver content on the finished sample was about 94ppm and after 50 times’ washes,the silver content of the fabric could remain above 87%.when the silver concentration of the AgNO₃ solution was 4ppm,6ppm and 8ppm,even after 50 times’ washes,the silver content of the silk fabric could all remain above 85%,which showed that there was a fine washing durability.That’s mainly because it’s multi-layer structure in fibroin.In the out layer amorphous area accounts for a high proportion than the crystalline area,which is more in the inner part of the fibroin.And there are random coil,α-helix andβ-sheet structure in the out layer which may wrap silver particles tightly.Of course there were Chemical bond combinations such as the complex structure between silver particles and fibroin.The dry process in the in-situ method of reducing silver ions in the fabric was also studied. The results showed that dry process had worse washing durability than streaming process.When the silver concentration of the AgNO₃ solution was about 6ppm,the silver content on the finished sample was 212ppm and only 133ppm left after 5 times’ washing,remained only 63%.Compared with streaming process,there was 250ppm silver on finished sample and 90%left after 50 times’ washing.The antibacterial activity of the finished silk fabric was also investigated using Gram-negative bacteria E.coli,and Gram-positive bacteria S.aureus.Results indicated that the finished silk had a very good antibacterial activity.When the concentration of the silver in AgNO₃ solution was about 2ppm,that’s to say,the silver content of the finished silk fabric was about 94ppm,no colony of the two bacteria was detected in the culture dishes in our antibacterial experiment.While there was a bit of colonies of the two bacteria when the finished silk was washed 5times,10 times and 50 times,the inhibition of the E.coli and S.aureus was still 99.999%.When the concentration of the silver in AgNO₃ solution was 4ppm,6ppm and 8ppm,there was no colony of the two bacteria in the culture dishes even after 5times,10 times and 50 times washes.