Antibacterial Modification Of Cellulosic Substrates Based On N-halamines/quaternary Ammonium Salts

Pathogenic microorganisms widely exist in the environment,and have a negative impact on people's daily life.A lot of antibacterial materials have emerged in recent years to resist harmful microbes and protect human's health.The antibacterial agents used in these materials mainly include metals and their oxides,quaternary ammonium salts,chitosan,N-halamines,etc.N-halamine has attracted a lot of attention due to its high efficiency,long-lasting and rechargeable antibacterial property.Quaternary ammonium salt is also a kind of water-soluble antibacterial agent that was commonly used in daily life.With the increase of human's demand for antibacterial materials and the enhancement of microbial resistance,it is necessary to develop new type of composite antibacterial agents,which can be used to prepare highly effective antibacterial materials.Based on the contact oxidation mechanism of N-halamines and electrostatic affinity of quaternary ammonium salts,it is proposed to finish N-halamines and quaternary ammonium salts onto cellulosic matrix,explore the effect of electrostatic affinity of quaternary ammonium salts on the antibacterial property of N-halamines,and prepare new kind of efficient antibacterial materials.5,5-Dimethyl-3-(3'-triethoxysilylpropyl)hydantoin(SPH)and 3-(triethoxysilyl propyl)octadecyl dimethyl ammonium chloride(SPODA)were used to modify cotton fabrics via pad-dry-cure(PDC)process and pad-dry(PD)process.Antibacterial test showed that Cotton/SPH-Cl/SPODA treated by PDC process could inactivate 0.65 log(65.32%)of E.coli within 30 min,while the antibacterial property of Cotton/SPH-Cl sample treated via PDC process was relatively lower with only 0.46 log of E.coli inactivated.The antibacterial property of cotton/SPH-Cl/SPODA treated via PD process was higher than that of cotton/SPH-Cl treated via the same process.It can be concluded that a synergistic effect existed between SPH-Cl and SPODA.The antibacterial properties of Cotton/SPH-Cl and Cotton/SPH-Cl/SPODA treated both with PD process were higher than the samples prepared by PDC process,which might be due to the difference in hydrophilic property.It was also found that the anti-UV property of SPH-Cl was poor,which could be improved significantly with the introduction of titanium dioxide.With the high cost,potential risks,and the low antibacterial properties when using PDC process,this proposal need to be further improved.(3-acrylamidopropyl)trimethylammonium chloride(APTMAC),containing both N-halamine precursor structure and quaternary ammonium group,was chosen to graft cotton fabrics via radical polymerization method,in order to improve antibacterial property,reduce the cost,and improve the production safety.The optimum process conditions were determined.Antibacterial test showed that cotton/ATAC-Cl could inactivate 5.82 log of S.aureus and 6.26 log of E.coli within 5 min.In addition,there was little effect on the thermal stability and tensile strength of treated samples,while the washing stability decreased.Even through there was no organic solvents used in finishing process and the antibacterial property was enhanced,monomer self-polymerization leads to low utilization rate of monomer which was disadvantageous in practical application.Layer-by-layer deposition method,known as electrostatic self-assemble method,was used to modify cotton fabrics,in order to improve the utilization rate of raw materials,and expand the application scope of ATAC.Polymeric ATAC and another anionic polymer contaning sulfonic acid group were coated onto cotton via layer-by-layer method,and the treated sample became antibacterial after chlorination.Cotton-(PATAC/PAMSS)5-Cl with 0.36 wt% oxidative chlorine could inactivate 100% of S.aureus and 99.73% of E.coli within 30 min.The washing stability of cotton-(PATAC/PAMSS)5-Cl was good,and the chlorine retention rate was 26% after 50 times washing circle.The treated fabric showed good sweat-washing stability and storage stability.The skin irritation test exhibited that these two N-halamine polymers had no irritation to the skin,and could be used safely.Microcrystalline cellulose and nanocrystalline cellulose are obtained by acid hydrolysis of cellulose materials,which are widely used in the filed of materials.N-halamine agent was not reported in antibacterial modification of microcrystalline cellulose and nanocrystalline cellulose.Therefore,in this part,methyl acrylamide was grafted on them via radical polymerization method.XRD analysis showed that the grafting took place only on the surface and did not cause serious damage to the crystalline region and the thermal stability.Antibacterial test showed that MCC-g-MAM-Cl could inactivate 5.70 log of S.aureus and 6.26 log of E.coli within 10 min.MCC-g-MAM-Cl also showed good storage stability.The modified nanocrystalline cellulose particles,NCC-PMAMs,were then incorporated into cellulose acetate films,and the film became antibacterial after chlorination.The composite films with 1.0% NCC-PMAMs showed enhanced tensile strength.But the elongation of the film decreased,and the film became brittle.CA/NCC-PMAMs-Cl-1.0 showed effective antibacterial property,with 6.04 log of S.aureus inactivated within 10 min and 6.27 log of E.coli inactivated within 5 min.The composite film with good biocompatibility has potentials for practical application.Quaternary ammonium salts were also used for antibacterial modification of nanocrystalline cellulose.Three kind of quaternary ammonium salts with different chain length were grafted onto nanocrystalline cellulose,and then the modified nanocrystalline cellulose particles were incorporated into chitosan films to prepare chitosan/ nanocrystalline cellulose composite films.Tensile strength test showed that the composite films exhibited enhanced tensile strength,when 5.0% of modified nanocrystalline cellulose was added,with 11%,18%,and 29% improvement for CS/NCC-EPTMAC-5.0,CS/NCC-DMDEPAC-5.0,and CS/NCC-DMOEPAC-5.0,respectively.The antibacterial property of CS/NCC-EPTMAC-5.0 was poor,while that of CS/NCC-DMDEPAC-5.0 and CS/NCC-DMOEPAC-5.0 were excellent,all the inoculated bacteria were killed within 30 min.