Preparation And Application Of Functional Membrane Based On Chitosan

Amino and hydroxyl groups on the chitosan have strong chemical activity which can react with various chemical groups to generate various derivatives, composite materials and so on. In recent years, there are many chemical methods to modify chitosan. The water-solubility of chitosan can be improved by modification.The quaternary chitosan Cs-QAS with different degrees of substitution was prepared with self-made quaternary ammonium salt at certain experimental conditions. The chitosan and quaternary chitosan were mixed together to get composite film, The crosslinking agents, such as glutaraldehyde and WD-50were used to crosslink the composite film to improve its resistance to acid and base, and reduce the swelling property of the hybrid membranes in water. The mechanical property of the composite film was improved by adding inorganic carbon nanotubes. The antimicrobial, water repellent functional composite film was prepared with the surface fluorination technique. The hybrid membranes were characterized by XRD, SEM, thermal analysis. In addition, compared with the unmodified chitosan, the antibacterial properties of the modified quaternary ammonium chitosan, and the hybrid chitosan films were all measured, and the mechanical property of them were also evaluated.The results show that the quaternary ammonium chitosan was prepared with the self-made quaternary ammonium salt. By orthogonal experiment, the suitable modifying conditions were obtained, such as molar ratio of chitosan and quaternary ammonium reagent1:3, pH9at75-80℃, the reacting time is8-12hours. At this condition, the quaternary ammonium chitosan with a higher yield and degree of substitution was obtained. The antibacterial property of the quaternary ammonium membrane to Escherichia coli and Staphylococcus aureus reached more than95%. The composite membrane was prepared by blending quaternary chitosan acetate solution and quaternary chitosan. Compared with the pure chitosan membrane, the antibacterial and mechanical properties of the composite membrane were improved. After surface fluoride treatment, the waterproof of the hybrid membrane was also improved. The membrane was treated in perfluorinated sulfonyl fluoride solution,30%mass concentration, for1h, at80℃, and baked at100℃for3minutes. After the treatment, the water contact angle of the modified membrane was increased from83°to around130°. In addition, the swelling property and dimensional stability of the hybrid membrane in water were also improved.