Dyeing of Wool Yarn with Aqueous Extract of Opuntia ficus-indica Fruit Containing Betalain Colorant Employing Ascorbic Acid as a Bio-mordant Under Varied Circumstances of Dyeing

Abstract

Opuntia ficus-indica well adapts to extreme climate conditions and grows rapidly in low water and poor soil requirement. In this study, the Opuntia ficus-indica fruit was used for natural dyeing of wool yarn. The Opuntia ficus-indica fruit has a reddish-purple color, due to the presence of water-soluble betalain colorants. When using this fruit as a natural dye, it is possible to obtain various color shades, because its color changes depending on the dyeing conditions. However, it is difficult to control the dyeing environment to reproduce the original color of Opuntia ficus-indica fruits. The aim of this study is to examine the effect of various dyeing conditions on the color strength, and color shades of Opuntia ficus-indica fruit. Ascorbic acid as a bio-mordant was applied for enhancing the stability of the betalain colorants. For this purpose, the betalain dye was extracted from Opuntia ficus-indica fruit by an aqueous extraction and used for dyeing wool samples in the presence of ascorbic acid at different dyeing process conditions. The dyed wool samples presented a red, pale red, orange, pale brown, and brown color by varying the applied pH (3, 5.5, and 8) of the dye bath, and dyeing temperature (40, 65, and 90 °C). Applying ascorbic acid as an antioxidant enhanced the color strength (~ 110%), thermal stability (~ 22%), and color fastness values. In addition, the presence of ascorbic acid did not have any significant effect on the tensile properties of the dyed wool yarns.