A Study on the Dye Fixation Mechanism of Waterborne Polyurethane

Abstract Waterborne polyurethane (WPU) has been widely used in the field of dye fixation and different fixation mechanisms have been proposed. However, questions on the impact of each fixation mechanism on dye fixation and the internal relationship between each mechanism remained. In this work, three cationic WPUs (CWPUs) and three non‐ionic WPUs (NWPUs) were first prepared to answer the question whether the fixation performance of non‐ionic WPU was necessarily worse than that of cationic WPU with similar composition. Two kinds of reactive CWPUs, including epoxy and isocyanate end groups, were prepared to investigate whether the reactive groups on WPU‐type dye fixing agent reacted with the groups on the fabric. A small molecular cationic dye fixing agent derived from the hydrophilic cationic chain extender of WPU was also synthesized, aiming to explore the relationship between the mechanisms of film formation and the formation of color lake.