| With the increasing attention to the problem of environmental pollution and energy shortage,the research and development of biomass resources has become one of the important topics of sustainable development.Cellulose is the most abundant natural renewable resource on the earth.It has many advantages,such as abundant sources,non-toxic and harmLess,and good biocompatibility.It has been applied in the fields of environment,energy,national defense,medical treatment and so on.However,cellulose is a macromolecular polysaccharide composed of glucose,which can easily be degraded by the erosion of bacteria and microorganisms in the environment,resulting in the degradation of cellulose products and the shortening of their service life,thus limiting their application.Therefore,the antibacterial modification of cellulose materials It is of great significance.In this paper,the antibacterial properties of cellulose were given by physical blending and chemical grafting.Sorbic acid was blended into cellulose/LiCl/DMAc homogeneous solution by physical blending,and then the film was prepared by impregnation precipitation phase inversion method.Chemical grafting method is to graft sorbic acid onto cellulose molecule by DCC condensation method,and then the film was prepared by impregnation precipitation phase inversion method.The structure and properties of the samples were characterized by FTIR,NMR,XPS,XRD,TG and DSC,and the antibacterial properties of cellulose films against Escherichia coli and Staphylococcus aureus were evaluated by colony counting method.Specific research contents are as follows:(1)Pulp cellulose was dissolved in LiCl/DMAc system to obtain uniform cellulose/LiCl/DMAc solution,and the Sorbic acid of different proportions was physically blended with cellulose until sorbic acid was completely dissolved in cellulose homogeneous solution.Last Sorbic acid/cellulose blend film ss were prepared by dipping precipitation phase conversion method.The structure and properties of Sorbic acid/cellulose blend films were characterized by FTIR,XRD,TG and DSC.The results showed that the thermal stability and crystallinity of sorbic acid/cellulose blend filmss were slightly decreased compared with pure cellulose filmss,and the tensile strength and elongation at break of the film decreased,With the increase of sorbic acid content,the tensile strength of the blend filmss increased first and then decreased.The bacteriostatic rate of the blend filmss to Escherichia coli and Staphylococcus aureus reached 12.8%-71.4%and 44.2%-80.8%.Furthermore the antibacterial activity of sorbic acid/cellulose blend films was greatly decreased after soaking in water/ethanol.(2)Cellulose sorbate was prepared by esterification of sorbic acid with cellulose by DCC condensation method.The effects of molar ratio,reaction temperature and reaction time on the degree of substitution of cellulose sorbate were studied.The optimum experimental conditions are as follows:reaction temperature was 80 C,molar ratio of-OH:sorbic acid in cellulose was 1:2,reaction time was 8 h.At this time,the degree of substitution of the product is 1.73.The film was prepared by impregnation precipitation phase inversion method.The results showed that cellulose sorbate film was successfully prepared,but the esterification process would result in the change of cell type and crystal structure of cellulose.The Cellulose sorbate film showed amorphous structure and the introduction of sorbyl group reduced or destroyed the hydrogen bond in and between cellulose to a certain extent,which resulted in a slight decrease in the thermal stability of cellulose sorbate film.The results of antimicrobial test showed that the inhibition rates of cellulose sorbate film on Escherichia coli and Staphylococcus aureus were 90.4%?100%and 99.2%?100%respectively.Especially,the antimicrobial effect of cellulose sorbate film on Staphylococcus aureus was better than that on Escherichia coli. |
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