Dyeing Performance Of Direct Dye On Ramie Fiber In Water And Liquid Ammonia Medium

Traditional printing and dyeing technology has some problems that cause environmental pollution,large waste water discharge,and the csomplex organic matter in the wastewater which is not easy to remove.In this research,the dyeing performances of ramie loosed fibers with direct blue 71 and direct red 23 dyes in liquid ammonia medium were studied.The dyeing performance of ramie fibers in liquid ammonia medium were investigated and compared with those of dyes in water medium.In the water medium dyeing,under the conditions of different dyeing temperature,dyeing time,dye concentration and sodium chloride content,the effects of dyeing conditions on degree of exhaustion,degree of fixation and wash fastness were investigated.The dynamics and thermodynamics of the dyeing process were analyzed.The experimental results showed that sodium chloride effectively increased the degree of exhaustion and fixation of ramie fiber,but did not have effect on the wash fastness.With the increase of dyeing temperature,the time of dye reached the equilibrium was faster.With the increase of dye concentration,the degree of exhaustion and fixation showed decreasing trends.In the dynamics aspect,the dyeing processes of direct blue 71 and direct red 23 on ramie fibers followed the quasi-second order kinetic model.The half-dyeing time of direct blue 71 is longer than the direct red 23.Under the condition of adding salt,the dyeing rate of dye was faster than that of dyeing without salt.The higher the temperature,the shorter the dyeing time,the higher the diffusion coefficient,the faster the dyeing rate,and the lower the activation energy.In thermodynamics,the dyeing process of direct dyes on ramie fibers was in accordance with the Freundlich adsorption model.In liquid ammonia medium dyeing,the effects of dyeing conditions on degree of exhaustion,degree of fixation and wash fastness were investigated under the different dyeing times,dyeing temperature and dye concentration.The dynamics and thermodynamics of the dyeing process was analyzed.The results showed that the degree of exhaustion of ramie fiber increased with the increase of dyeing time,and reached the dyeing balance after about 60 s.The dyeing temperature(-40? to-60?)had no significant effect on the degree of exhaustion.With the increase of dye concentration,the degree of exhaustion gradually decreased.In terms of degree of fixation,it increased with the time increase,and then fluctuates after dyeing equilibrium.The dyeing temperature had no obvious effect on the degree of fixation,and the degree of fixation decreased with the increase of the dye concentration.The wash fastness of ramie fibers showed a decreasing trend with the increase of dyeing time and dye concentration.The dyeing process of ramie fiber in liquid ammonia medium was consistent with that in water medium,which fitted the quasi-second order kinetic model and Freundlich adsorption model.