547.99+678.06 and L. S. Gal'braikh It was shown that incorporation of ethyl alcohol in acetic-acid solutions of chitosan reduces their turbidity and intrinsic viscosity and increases the dynamic viscosity more the higher the concentration of chitosan and the amount of alcohol added.Chitosan is processed into fi lms, granules, fi bers, and other items by dissolving it. Dilute aqueous solutions of acetic acid are usually used as the solvent as the cheapest and most available reagent that ensures formation of a water-soluble derivative of the polymer -chitosan acetate. However, the high boiling point of the solvent (>100°C) and relatively low concentration of spinning solutions with respect to the polymer (6%) in dry (thermal) spinning cause the low speed of the process.There are different methods of regulating the rate of evaporation of the solvent and hardening of the polymer. Using mixtures of solvents with different boiling points and mixtures of a solvent and precipitator is one method [1]. Despite the fact that such a method usually provides for "severe" spinning conditions and formation of a nonequilibrium and defective structure of the polymer article, in many cases its use is totally justifi ed. Great attention is being focused on formation of the pore structure in manufacturing separating membranes and fi bre sorbents, including bicomponent sorbents with a "core-shell" structure.There are few data on the effect of alcohols on the rheological properties of aqueous solutions of polymers, although we do know that incorporation of ethanol in aqueous solutions of polyvinyl alcohol and methylcellulose improve their solvation and inhibit gelation [2]. Addition of alcohol to cellulose acetate spinning solutions to reduce the viscosity and increase the homogeneity is also widely used [3].We investigated the effect of adding ethyl alcohol to acetic-acid solutions of chitosan on their structural and rheological properties and the quality of the chitosan shell applied on viscose fi bre to give it sorption capacity. We report the results of a comparative study of the structural and rheological properties of dilute and concentrated solutions of chitosan in acetic acid with and without ethyl alcohol.Ethyl alcohol was selected because of its good compatibility with water -the fundamental solvent, lower boiling point, and relative nontoxicity. The chitosan* used in the study had a molecular mass of ~1.710 5 , degree of deacetylation of 0.92, degree of crystallinity of ~45%, 100% solubility in 2% acetic acid, and ash content 0.2%.For the rheological studies, the solutions were prepared by preliminary swelling of the chitosan in water, dissolution in acetic acid and dilution with alcohol, the water-alcohol mixture, or water to attain a given concentration of polymer of 1-8 wt. % and an alcohol content of 10-40 wt. %. The alcohol, water, and water-alcohol mixture was added to the system by small portions while stirring vigorously to prevent precipitation of the polymer into sediment. Non-Newtonian acetic-acid solutions of ...
