Improved dyeing of poly-m-phenyleneisophthalamide using cationic dye based on macro-cation dyeing mechanism

A new dyeing mechanism based on macro-cation was proposed. To confirm this mechanism, the dyeing effect of the concentration of hydrogen bonding regulator, dimethylacetamide (DMAc), on the dyeing effect of poly-m-phenyleneisophthalamide (MPIA) fibers with cationic dyes was compared with that using neutral dyes. DMAc and NaCl can synergistically and selectively break the inter-molecular hydrogen bonds of MPIA. The color characteristics of dyed fabrics were measured and analyzed. The color depth of fabric dyed using cationic dye increases with increased DMAc and NaCl concentrations. Cationic dyes and DMAc form macro-cations, [DMAc-Dye](+), which facilitates the adsorption and subsequent fixing of dyes with MPIA fibers. And optimal dyeing effect shows two times of K/S value with cationic dyes than that with neutral dyes. More importantly, there is no deterioration in both the mechanical properties and thermal stability of the fabrics after dyeing. These findings can serve as a mechanistic guide for the selection of dyes for MPIA fibers.