Hydrophobic fibers are highly crystalline and non-polar polymers hence pose a big problem for dyers. Modified
acrylic fiber containing different amounts of amidoxime groups as a function of the nitrogen content was obtained and dyed
with curcumin and madder natural dyes. The dyeing parameters, such as dye concentration, dye bath pH, salt concentration,
temperature, and time and the effect of alum and ferrous sulfate used as mordants were investigated. Compared with the dyeings
obtained from modified acrylics, those of blank samples appeared less in color strength values. The color strength was
proportional to the nitrogen content of the sample and the maximum value was obtained at pH 2 and pH 5 using madder and
curcumin, respectively. The fixation of the dye molecules to the modified acrylic fibers was investigated to show mainly ionic
and physical bonds. The washing, perspiration, and rubbing fastness properties for the dyed samples were enhanced by application
of alum. The light fastness ratings were also improved using ferrous sulfate especially for the case of the samples dyed
with madder.