Effect of N,N‐diethyl‐m‐toluamide on the structure and dyeing properties of meta‐aramid and para‐aramid fibre

N,N-Diethyl-m-toluamide has been widely used in the mosquito-repellent finishing of textiles over the past few decades, but the use of N,N-diethyl-m-toluamide as a dye carrier for aramid dyeing with disperse dye has been seldom reported. Meanwhile, the application of aramid fibre in clothing is limited because it is difficult to dye. In this work, the effect of N,N-diethyl-m-toluamide on the dyeing properties of aramid fibre was examined by measuring the percentage disperse dye exhaustion under different conditions. In order to understand the mechanism by which N,N-diethyl-m-toluamide promotes the exhaustion of disperse dye on aramid fibre, the ultraviolet-visible spectrum of the dye and N,N-diethyl-m-toluamide solution, the glass transition temperature, the crystalline structure, and the degree of orientation of aramid fibre treated with N,N-diethyl-m-toluamide were measured by ultraviolet-visible spectrophotometry, differential scanning calorimetry, X-ray diffraction analysis, and velocity-oriented tests respectively. The results indicated that N,N-diethyl-m-toluamide not only could reduce the glass transition temperature and degree of orientation of aramid fibre but could also improve the solubility of disperse dye in aqueous solution, and therefore could enhance the percentage disperse dye uptake on aramid fibre, whereas treatment with N,N-diethyl-m-toluamide showed little effect on the crystalline structure of aramid fibre. The results implied that N,N-diethyl-m-toluamide was beneficial to the diffusion of disperse dye molecules into the amorphous region of aramid fibre under the dyeing conditions, but seldom affected the mechanical properties of aramid fibre.