Polyammonium salts as retardants for the dyeing of methylene blue on polyacrylonitrile microfibers

To reduce the dye uptake rate of cationic dyes on polyacrylonitrile (PAN) microfibers and achieve uniform dyeing results, synthetic double‐headed quaternary ammonium salts (BTAE‐12) and quadruple‐headed quaternary ammonium salts (PTAE‐12) were used as retarding agents. These were compared with the conventional retarding agent dodecyl dimethyl benzyl ammonium chloride (1227). The differences in exhaustion percentage of methylene blue‐dyed PAN microfibers were compared across three concentrations of the retarding agents. The regulatory effects of the retarding agents on the methylene blue uptake rate and dyeing transition temperature during the heating stage were investigated, and their influence on the dyeing kinetics of PAN microfibers was analysed. Results indicate that BTAE‐12 and PTAE‐12 exhibit superior retarding effects compared to 1227, with PTAE‐12 demonstrating better performance than BTAE‐12. Without compromising the final dye exhaustion percentage, the optimal concentrations for achieving the best retarding effects were approximately 0.4 mmol/L for 1227, 0.15 mmol/L for BTAE‐12 and 0.025 mmol/L for PTAE‐12. As the retarding agent concentration increased, the dyeing transition temperature gradually rose. As the number of quaternary ammonium cation groups in the dye‐retarding agent molecules increased, the dyeing rate constant gradually decreased, extending the time required to reach equilibrium.