Three natural yellow dyes, namely Rheum emodi, Gardenia yellow and curcumin, were applied to the simultaneous dyeing and functionalization of silk.
Their dyeing properties and functionalities as wellas the effects of post-mordanting on the hue, color fastness and functionalities of dyeings were com-pared, and the correlations between the chemical structures and application characteristics of dyes were revealed.
The three dyes exhibited large variations in dyeing and mordanting properties, and functional-ities. Curcumin displayed the greatest coloring power.
The uptake of Gardenia yellow was most sensitiveto the pH of dyebath. Gardenia yellow and curcumin had much higher building-up ability than R. emodiwith anthraquinone structures.
Gardenia yellow possessed the highest fastness ratings, while curcuminand R. emodi showed poor wet rub fastness and wash fastness for staining.
Curcumin imparted the highestantioxidant activity to silk because of its high adsorption and two phenolic hydroxyl groups in its struc-ture and also gave the highest UV protection ability.
Curcumin and R. emodi provided higher antibacterialactivities than Gardenia yellow.
The post-mordanting with ferrous and ferric salts exerted great influenceon the color parameters, color fastness and UV protection ability of dyeings.
This study points out thatthe common dyeing process of three natural yellow dyes can impart the color and functional propertiesto silk.