Study On Improvement Of Antibacterial Durability Against Washing Of Cotton Fabric By Controlling Fiber Surface Structure

Inorganic particles such as nanosilver and nanocopper particles,have been widely used in the production of antibacterial cotton fabrics due to their good antibacterial effects.However,it is hard to adhere them onto cotton fibers by covalent bonds,leading to poor washing resistance of the antibacterial function.Although a number of reports demonstrated several ways to improvethe antibacterial durability by increasing the amount of the antibacterial nanoparticles,the health safety and environmental problems caused by leakage of the metal particles could not be solved.Besides,organic antibacterial agents like hydantoin derivative have the advantages of high antibacterial efficiency,good stability and small odor,but the antibacterial effect decreases obviously with time,and it also lacks sufficient washability.Here,three binders of a chitosan derivative the modified by the a-ketoglutaric acid,L-cysteine and thioglycolic acid were selected to enhance the adhesion force of the inorganic nanoparticles with cotton fiber surface.Further,a new N-halamine derivative,3-Methylallyloxy-5,5-dimethylhydantoin was designed and synthesized.After a grafting polymerization on the cotton fiber surface using MIST polymerization method,the antibacterial function was introduced on the cotton fabric to achieve the durable function through its renewable property.This thesis includes the following four parts,(1)A chitosan derivative was synthesized by a reaction of chitosan with ?-ketoglutaric acid,and was used as a binder to immobilize silver nanoparticles and to enhance the washing durability of the antibacterial cotton fabric.It can covalently link with cotton fiber surface via esterification,and linke with the AgNPs by coordination bonds.As a result,the cotton fabrics with the chitosan derivative grafted on the fiber surface has good dispersion and adhesion to the AgNPs.They were uniformly distributed on the fiber surface and their average particle size is 39 um.The antibacterial rates against E.coli and S.aureus are higher than 99%.After 30 washing cycles,the bacterial reduction rates against both S.aureus and E.coli were kept at 95.4%and 96%,respectively.(2)L-cysteine was used as a binder to enhance the washing durability,its esterification reaction with the hydroxyl group of cotton fabric,and its coordination with AgNPs could stabilize the AgNPs on the surface of cotton fibers,leading to an enhanced washing durability of the antibacterial cotton fabric.As a result,L-cysteine has been successfully grafted,AgNPs have been successfully loaded on the surface of the fabric.They were uniformly distributed on the fiber surface and their average particle size is 33 nm.The antibacterial rates against E.coli and S.aureus reached 100%.After 30 washing cycles,the antibacterial rates remained at 100%.By comparison of(1)and(2)above,it is found that the thiol group has a better effect on nano silver than amino group.The efficient coordination can reduce the size of the AgNPs and can increase the adsorption surface area,leading to the improved durability of the antibacterial function(3)To further evaluate general ability of a thiol structure in binder to enhance the washing burability of an antibacterial fabric with inorganic nanoparticle coating.The results show that the antibacterial cotton fabric has good antibacterial properties and excellent washing durability.The antibacterial rates against both E.coli and S.aureus were over 99%,and even after 50 washing cycles,they still higher than 96%.(4)A new N-halamine derivative,3-Methylallyloxy-5,5-dimethylhydantoin was synthesized,and grafting polymerized onto the fibric surface to fabricate an antibacterial coating using a MIST polymerization method.As a result,by the repeated chlorination,the cotton fabric maintained the antibacterial effect for a long time.The antibacterial effect of modified fabric on escherichia coli and staphylococcus aureus was higher than 97%after washing for 30 times.The antibacterial rates against both E.coli and S.aureus were close to 100%,even after 30 washing cycles,they still higher than 97%In summary,based on the selection of the molecular structure of binder,the washing durability of the antibacterial cotton fabrics are improved by enhancing the adhesion force of the antibacterial nanoparticles on the surface of cotton fibers.It is found that thiol structure in the binders can achieve that through the coordination effect with the metal atoms.The research results can provide experimental data and theoretical basis for the future development and production of antibacterial cotton fabrics.