Influence of Internal Lipid on Dyeing of Wool Fibers

Abstract

Wool is a natural fiber that is mainly composed of protein. It has an external lipid content widely used in cosmetics (lanoline) and minor internal lipid content (1.5%), which could be of added value given its high content of ceramides. Internal wool lipids (IWL) were mostly extracted at laboratory level and the lipid composition was quantitatively analyzed. The hydrophobic character of both extracted and non-extracted fibers was evaluated. These wool fibers were dyed with two acid dyes with a different degree of hydrophilic character. Dyeing behavior and washing fastness tests were assessed to study whether the lipid extraction could affect fiber dyeing. The results obtained showed the different behaviors of extracted and non-extracted wool fibers when dyes with different hydrophilic character were used. Given the absence of surface hydrophobic differences between the two fibers, the different dyeing behavior may be attributed to the interaction between IWL and the dyestuff, highlighting the importance of dye penetration through the cell membrane complex. A lipid extraction could therefore modify wool dyeing strategies and reduce the final dyeing temperature without impairing the washing fastness of the fibers.