A Study On The Behaviors Of Chitosan Solutions

Chitin and chitosan are the most abundant organic polysaccharide on earth after cellulose. In recent years, they are widedly used in biomedical materials cosmetics, heavy metal ion absorbent textile industry and many other fields for their non-toxicity, biodegradability, biocompatibility and many other unique properties, and also because of they are linear polymer, has a good spinnability.But the low intensity of pure chitosan fiber (0.61-2.48g/dtex) limits its further application. At present, the chitosan fiber was mainly prepared by wet spinning. Due to the chitosan molecular in the acid solution is a cationic polyelectrolyte, its solution properties are quite different from the general polymer solution, and it will greatly influence the nature of chitosan fiber, which caused more and more attention. The molecular weight, concentration, temperature, acids, storage time and additives effects on the chitosan dope were discussed in this paper. Furthermore, the chitosan powder, films that prepared and chitosan fibers that purchased were characterized. The results showed that the decline of the pH value will let the solution viscosity downward trend more evident. Chitosan acetic acid solution with the temperature rises and the extension of storage time, cause the viscosity declines. With increased concentration of chitosan solution, solution viscosity increased. With the increase of the molecular weight of chitosan samples, the viscosity of solution were found increased.The results also showed that in dilute solutions Li+ was the most influencial factor on the viscosity of solution and in semi-dilute solutions Ba2+ was the main reason for their ionic radius and hydrate number. Both intrinsic viscosity and bulk viscosity of chitosan solution were found increasing with the amount of adding salts. However, urea tended to cause the decreasing of viscosity. The optimized s/c value of urea, N,N-diethyl urea and N,N-diethyl urea was 0.08, 0.05 and 0.08, respectively. While for urea, ethanol and acetone, the value was 0.8, 0.5 and 0.5. The results of static laser light scattering showed that the particle sizes of chitosan molecules in dilute solutions decreased by adding NaCl and LiCl·H2O and increased by adding urea.The characterization of chitosan powder, films prepared and chitosan fibers purchased by X-ray powder diffraction, IR and DSC showed that the crystalline structure of chitosan that used in this experiment wereα-type. And noncrystalline chitosan films with Mw=200,000 were achived by preparing under high temperature. Comparing with the crystalline structure of chitosan in chip form, the crystalline structure of chitosan fiber converted fromβ-type toα-type crystal. This might be the reason behind the low strength of chitosan fibers.