| Chitosan is the unique alkaline polysaccharide in the nature and also an environmental friendly natural macromolecule. Owning to its characteristics such as antimicrobial activity, biocompatibility, non-toxicity and biodegradability, chitosan can be applied in many fields, such as pharmaceutical and medical applications, environmental protection, textiles, wastewater treatment, biotechnology, cosmetics, food processing and agriculture. However, chitosan can be only dissolved in a few dilute acid solutions, and this limits its applications, because of its rigid crystalline structure. This article would be begun by the study on the solubility of chitosan to broaden the field of application of the chitosan. By the tests of solubility of chitosan, the factors and the structure characterization showed that chitosan had about 4% mass loss in the solution of NaSCN and the temperature and the concentration of the solution of NaSCN played an important role in the solubility of chitosan while the concentration of chitosan and the molecular weight of chitosan played a small part. The characterization of 1HNMR for chitosan indicated that the soluble chitosan in the solution of NaSCN also had the fine structure. And the characterization of FT-IR proved that the chitosan kept the intrinsic properties and structure.By means of the chemical modification, two water-soluble chitosan, O-CMC and HTCC, were prepared. The blend film and fiber of modified chitosan and polyacrylonitrile were obtained by using the method of coagulation, which showed that the two materials had good miscibility. The spectrum of the FT-IR of HTCC/PAN fiber had little difference. The reason might be that the water-soluble chitosan had the water loss and the chitosan possessed similar structure with the polyacrylonitrile in the FT-IR spectrum. The DSC spectrum of the blend film of HTCC/PAN and O-CMC/PAN had only one Tg, showing that the two system had good miscibility. Also, the Tg of the blend films increased following the addition of the modified chitosan. The crystallinity of the blend films increased with small amount of modified chitosan and decreased following the excessive amount. The evaluation of the blend films of HTCC/PAN exhibited good antibacterial property, by the tests of the criterions of the Japanese JIS Z 2801:2000 and the Chinese QB/T 2591-2003 and had the high antibacterial rate with 99.99%.Finally, we emphasized to study the factors and characterization of the graft copolymerization of chitosan with acrylonitrile and broadened the application of the graft product using the method of spinning. Graft copolymerization was confirmed by FT-IR spectra, X-ray diffraction and 1HNMR spectra measurements. The crystalline of product was due to that the graft PAN had grew into enough long chain to form the regular crystalline region during the graft copolymerization. The characterization of 1HNMR also offered a kind of method of the NMR of the chitosan and the product. In the range of 310-800℃, carbonization occurred in the graft copolymer from the TGA.The graft reaction conditions were investigated in detail to obtain a high efficiency of grafting, including the concentration of chitosan, reaction temperature, initiator concentration. The rate of grafting all had a maximal value. The optimum reaction conditions at the highest graft ratio and efficiency of grafting were obtained at [AN] 0.9 mol/L, [CS] 13.3 g/L, [Initiator] 0.006 mol/L,62±1℃and 2 h. We did the spinning experiment to explore the graft product using the single fiber tensile strength tester to measure the tensile property, which was founded that the tensile property of the fiber by the post-processing was better than the as-spun fiber. So, the graft copolymer is promising for fabrication of acrylic fibers as a kind of functional additive. |
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