Controlling supermolecular structures and improving colorfastness in cotton fibers

Abstract

A new discovery was made in which commercially available triethanolamine could reduce the lattice volume of the supermolecular structure of cotton from the periphery of the lattice by moving cellulose chains on the surface of the crystallites to the amorphous regions, thereby decreasing the close-packed crystallization volume and leading to an increased free volume of the amorphous regions. Subsequently, several supermolecular structures for cotton fibers were successfully controlled to improve the colorfastness in cotton fibers at the molecular level. With the decrease in the degree of crystallinity, more unfixed dyes could be removed by washing reagents, whereas the remaining dyes were mostly fixed to the cotton by covalent bonds, causing a stronger colorfastness, with the best wet rubbing fastness reaching a relatively permanent grade 4. Moreover, the effect mechanism revealed that the unfixed dyes were detached from the cotton fibers according to the reverse process of the adsorption models and that there were additional methods for the unfixed dyes in the fibers to be removed in the presence of triethanolamine than when using pure water. In addition, the binding forces of dye adsorption in the cotton fibers decreased, while the entropy of dye adsorption was higher than that measured when using pure water. Thus, the results suggested that controlling the supermolecular structures of the cotton fibers promoted the removal of unfixed dyes from the fibers and achieved improved colorfastness.