Anti-dissolution and dyeing properties of Al-modified alginate fibers

Alginate fibers made from seaweed have some desirable properties as textile materials, but they also have two shortcomings that limit their usages: they are intolerant to salt, alkali, and detergent, and they are difficult to dye due to the electrostatic repulsion with anionic dyes. To solve the two problems in this project, a process of successive modification of alginate fibers using sodium pyrophosphate, alum, and sodium hydroxide was developed. SEM images and ion content of the modified alginate fibers showed that the fibers did not dissolve in high concentrations of sodium chloride, sodium hydroxide, or standard detergent solution and still maintained their original morphology. Also, the results of FTIR, XPS, XRD, and single-fiber strength tests indicated that the modification process enabled the alginate fibers to form a new tetrahydroxy cross-linking structure and thus improved their mechanical properties. The tetrahydroxy cross-linking structure prevented the dissolution of alginate fibers by blocking the exchange of ions between the fibers and the solution. Besides, the presence of Al³⁺ in the tetrahydroxy cross-linking structure modified the electrostatic repulsion between the alginate fiber and the anionic dye, resulting in high dyeing and dye fixation rates. Thus, the modified alginate fiber can be dyed directly with common dyes without dissolution, solving the above-mentioned two problems. This can enormously expand the potential usages of alginate fibers and therefore has significant academic and practical implications.