Fixation of a Direct Dye on Cotton Using a Cellulose Thiocarbonate/ammonium Persulphate System

A cotton fabric was treated with thiocarbonate by reaction with carbon disulphide in the presence of sodium hydroxide. This thiocarbonate-treated cellulose, as well as alkali-treated and untreated cellulose, was dyed with a direct dye in the presence of ammonium persulphate under a variety of conditions. The colour strength and extent of fixation of the dyed fabric was examined. The thiocarbonate-treated cellulose exhibited high colour strength and better dye fixation than either the alkali-treated or untreated cellulose. This was explained in terms of the involvement of the thiocarbonate groups together with ammonium persulphate in the formation of covalent bonds between cellulose and dye by a free-radical mechanism. The mechanisms of bonding between cellulose and direct dye are suggested