Effect of pretreatment with polar solvent on the dyeing and mechanical properties of meta-aramid fibers
Meta-aramid fibers are known to be difficult to dye because of their high crystallinity and compact structure.Pretreatment with polar organic solvents can well swell meta-aramid fibers,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 the 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 the mechanical property was investigated,and the effect of dyeing temperature on the dyeing performance was studied.Besides,15 disperse dyes were applied to dyeing meta-aramid fabrics 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)and dimethyl sulfoxide(DMSO)was 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 fabrics with C.I.disperse red 167,the dye exhaustion value was largely improved with the increase of the pretreating temperature and prolonging of the pretreating time.A temperature of 55 ℃ and a time of 30 min were optimized for the pretreating process.Further investigation of the 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,results 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 penetrate 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 is concluded that the damage of mechanical property of a pretreated meta-aramid fabric can be well reduced by using a low-temperature pretreating process.Therefore,it is feasible to obtain a dyed meta-aramid fabric with both satisfactory dyeing performance and mechanical property.
万方数据
维普
