Dyeing chitin/cellulose composite fibers with an acid dye

The dyeing properties of a chitin/cellulose composite fiber, Crabyon(R) (CR), for CI Acid Orange 7 dye are examined at equilibrium compared with those for protein fibers of silk and wool and a regenerated cellulosic fiber, viscose rayon. The adsorption isotherms of the dye by CR are the sigmoid type, different from silk and wool, which are the Langmuir type. The most remarkable feature Of CR is its adsorption of the dye, which greatly depends on the dyebath pH. Hence, it seems that the adsorption is due to the electrostatic interaction of the dye anion with the protonated amino group of the partially deacetylated chitin in CR. Under the same conditions, the greater the content of the basic groups in amorphous regions in the substrate, the greater the dye uptake at equilibrium: CR(20) > Wool > CR(10) > silk greater than or equal to CR(3).