关键词: 间位芳纶, 预处理, 染色性能, 分散染料, 机械性能

Abstract: Meta aramid fiber is known to be difficult to dye because of its high crystallinity and compact structure. Pretreatment with polar organic solvents can well swell meta aramid fiber, thus facilitating the dyeing process. Reported papers usually proceed the pretreatment at high temperature, leading to a severe fabric shrink accompanied with a remarkable decline of mechanical property. Therefore, it is important to balance the relationship between dyeing performance and mechanical property. The aim of this paper is to explore the feasibility to decrease the fabric damage by studying the effect of pretreating/dyeing process on dyeing/mechanical properties.
 In this paper, the mechanical property of a meta aramid fabric was assessed by shrinkage rate, breaking strength and elongation values, while the dyeing property was evaluated in terms of dye exhaustion, color depth as well as color fastness. The pretreating and dyeing processes were optimized. The effect of pretreating temperature and time on mechanical property was investigated, and the effect of dyeing temperature on dyeing performance was studied. Besides, 15 disperse dyes were applied to dyeing meta aramid fabric at optimized pretreating and dyeing condition. Moreover, scanning electron microscope (SEM) was also used to analyze the fiber surface.
 Pretreatment with polar organic solvents, such as N, N-dimethylformamide (DMF), N, N-dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), etc. were confirmed to efficiently improve the dyeing performance of meta-aramid fabrics, while DMSO was demonstrated to be the best solvent when compared with others at the same pretreating condition. When dyeing the pretreated meta aramid fabric using C.I. disperse red 167, the dye exhaustion value largely improved as increasing the pretreating temperature and prolonging the pretreating time. A temperature of 55 ℃ and a time of 30 min were optimized for the pretreating process. Further investigation of dyeing process indicated that a dyeing temperature of 80 ℃ and a time of 60 min were enough to obtain a high dye exhaustion value of 95.1%. Under the optimized pretreating and dyeing conditions, result of dyeing experiment suggested that azo type disperse dyes generally exhibited better dyeing performance than anthraquinone or heterocycle type disperse dyes. The dyed meta aramid fabrics also showed good to excellent color fastnesses to soaping, rubbing and sublimation of higher than grade 4. In term of mechanical property, the pretreating temperature was found to be the primary key factor. High temperature would help the polar solvent penetrating into meta aramid fiber, breaking down the hydrogen bonds, thus swelling the fiber. In particular, when pretreated at 55 ℃ for 30 min, the shrinkage rate of a meta aramid fabric could decline to less than 10% with a breaking strength of 950 N and elongation value of 36%. SEM image analysis further showed that pretreatment at relatively low temperature would effectively avoid solvent erosion on fiber surface. In addition, most of the dyed meta aramid fabrics exhibited breaking strengths of 956~1110 N, showing a comparative mechanical property as the untreated fabric.
 Based on the above results, it was concluded that the damage of mechanical property of a pretreated meta aramid fabric could be well reduced by using a low-temperature pretreating process. Therefore, it was feasible to obtain a dyed meta aramid fabric with both satisfactory dyeing performance and mechanical property. 

Key words: meta aramid, pretreatment, dyeing property, disperse dye, mechanical property