Enhanced dyeing properties of gardenia yellow on cotton with siloxane-based medium

Decamethyl cyclopentasiloxane (D5) was devoted to the medium in the dyeing process of gardenia yellow on cotton fabric to improve the dyeing properties. The effects of D5 percentages and mordants, dyes dosage as well as dyeing temperature and time on dyeing properties were investigated. The results show that optimal dyeing processes of gardenia yellow on cotton in a siloxane-based medium are as follows: D5 percentages 94%vol, dye dosage 2% (o.w.f), alum as mordant dosage 3% (o.w.f), dyeing temperature 80 degrees C, dyeing time 40 min. Compared with water dyeing, cotton fabrics dyeing with D5/water present enhanced color strength (K/S value) and fine levelness. By fitting the dyeing curves, it is found that dyeing mechanism of gardenia yellow on cotton in D5 follows a pseudo-second-order kinetics model, which is alike to the dyeing kinetics in water. Owing to the hatred of D5, gardenia yellow is rapidly absorbed on the cotton fiber in initial dyeing process, then diffuses and reacts with cotton, which is drived by the diffusive force inducing by the concentration differences of dyes between dye liquor and fiber. In addition, the color fastness of cotton fabrics dyeing with D5/water is equal to that dyeing with water. This dyeing technique that immensely reduces dyeing wastewater has potential application in natural dyestuffs.