Reactive dyeing of ramie yarn washed by liquid ammonia

The washing efficiency of water, nonionic soap solution, reflux solution, pure liquid ammonia (99.99%), and solvated liquid ammonia was studied on dyed ramie yarns. The ramie yarn samples were dyed with a 2% on weight of fiber (o.w.f) shade with five types of reactive dye by the classical exhaustion method. The washing performances of these solvents were quantified by the dye removal rate, the color uniformity, and the color fastness properties (washing, rubbing, and lightness). Furthermore, the influence of these wash methods on the physical properties of the final yarn samples including shrinkage, tensile strength, and elongation was schematically examined. The results of these measurements revealed that the dye removal rates during the washing in pure liquid ammonia and solvated liquid ammonia were lower than the yarn washed in water, soap solutions, or reflux solutions. The color uniformity (expressed as the standard deviation of K/S values for all dyed ramie yarns) was within the acceptable limits with the satisfactory color fastness levels. The shrinkage values of yarns that were washed in the pure liquid ammonia and the solvated liquid ammonia were both similar (9.0%) and considerably higher than the samples washed in water (1.8%), soap solution (2.4%), or reflux solution (2.6%). The tensile strength and the elongation of the resultant yarns improved significantly when the samples washed in pure liquid ammonia. The yarns that were washed in the solvated liquid ammonia solutions had decreased tensile strength and elongation. The cause of the decrease was determined by the XRD measurements, which confirmed that the crystallinity, and the orientation of these fibers decreased dramatically after being washed in the ammonia system solutions. The samples that were washed in the liquid ammonia had a smoother surface morphology than the other washing processes.