The Study Of Wet-dry Spinning For Crosslinked Chitosan Fibers

Chitosan is the only alkaline polysaccharide polymer which is positively charged in the nature. It’s production is next to cellulose in nature, which makes it to be a kind of ecological environmental protection and renewable resourse. Chitosan has the ability of good adsorption, film and fiber forming, good moisture absorption, is widely used in biomedical and high-grade fabrics. Chitosan fibers can be widely used in absorbable surgical sutures, carrier of tissue engineering, wound dressing and so on, but the low strength limit the use range of chitosan fiber greatly. So the methods by improving spinning method and the chemical modification to improve the mechanical properties of the chitosan fibers has become the focus of research.In order to improve the mechanical properties of chitosan fiber, we use dry-wet spinning method to replace the traditional wet spinning, and add epichlorohydrin in the dope, to prepare the crosslinked chitosan fiber in one step. This paper studies the performance of chitosan spinning dope and discussed the urea effection on the properties of chitosan dope. In order to improve the mechanical properties of fiber, a air layer is added between the jet mouth and the coagulation bath. SEM analysis is used to compare the influence of different length of air layer to the mechanical properties of chitosan fibers. Epichlorohydrin is added directly to the spinning dope, and the effect of the concentration of epichlorohydrin, cross-linking time and reaction temperature is discussed. And infrared spectrum and X diffraction are used to characterized the chemical structure and crystalinity of crosslinked fibers, the experiment result shows that:1.The analysis of chitosan raw materials used in this paper shows that, the moisture content is6.57%, ash content is0.65%, the deacetylation degree is90.33%and the molecular weight is9.5×104.When the mass fraction of chitosan in constant, all this method can be used to reduce the viscosity of spinning dope by raising temperature, increasing the concentration of acetic acid and adding urea to the dope.2.By adding urea into the spinning dope can cause the change of chitosan molecular conformational. With the increase of urea, the viscosity of chitosan dope drops, and it drops quickly at first, later become slowly and increase at last. As the chitosan concentration increases, the appropriate increase of urea content is helpful to reducing the viscosity of chitosan dope.3.The dry-wet spinning can helps to denser the structure of chitosan fibers. The SEM shows that, the air layer is important to the improvement of orientation degree. When the mass fraction of chitosan is6%, the best length of air layer is4cm. As the axial tensile and the thermal motion happens at the same time, a proper length of air length is required.4.The best spin conditions for6%chitosan dope is coagulation bath temperature20～30℃, NaOH concentration is15%, the coagulation bath compose is15%NaOH and30%anhydrous ethanol, the length of air layer is4cm.5.The infrared spectrum analysis of chitosan shows that, the reaction of chitosan and epichlorohydrin happened on C6-OH. When the temperature is above40℃, the crosslinking reaction happens in large amounts. X-ray diffraction shows that the crosslinking reaction destroy the regularity of the macromolecular chain, change the crystal type from a to B, which lower the crystalinity of fibers. And the best crosslink condition is,the concentration of epichlorohydrin is1.0×10-2mol/L, crosslink time is40min, crosslink temperature40-50℃.6.The crosslinked fiber performances well in the moisture absorption, the hygroscopic and moisture regain rate is13.09%, the moisture regain is17.38%, the hygroscopic hysteresis is4.29%, far more than1.78%of the cotton. The hygroscopic hysteresis of fibers is associated with moisture absorption ability, generally fiber which has a high hygroscopic hysteresis also has a good hygroscopicity, which proved that chitosan fibers has a good hygroscopicity.7.Antibacterial experiments shows that chitosan fibers have a good bacteriostatic action on escherichia coli and staphylococcus aureus. The crosslinked chitosan fibers still maintain the original antibacterial properties which makes it possible to be widely used in the development of anti-bacterial textiles.