Influence of ethanol–alkali mixture on the structure of chitosan fibers and film coatings

Abstract

Structural features of films and fibers obtained from mixtures of a chitosan solution in acetic acid with an ethanol and NaOH solution were investigated. Phase separation in the system that included chitosan, acetic acid, ethanol, NaOH and water was studied using scanning electron microscopy and time dependence of optical density. Optical densities of the mixtures were measured at λ = 330 nm. Structural studies involved two types of films: (a) the samples obtained from the mixtures of the chitosan solutions and various precipitants by lyophilization; and (b) the samples obtained by drying at room temperature. It was demonstrated that the most stable structure is formed upon the mixing of the chitosan solution with the ethanol–alkali mixture. Chitosan fibers prepared by wet spinning had the following characteristics: tensile strength σ = 188 ± 9.1 МPа; Young’s modulus E = 11.5 ± 0.6 GPа; tensile strain ε = 4.8 ± 0.6%.