Natural dyeing of cotton with Xylocarpus granatum bark extract: Dyeing, fastness, and ultraviolet protection properties

Abstract

In this research we investigated the dyeing of cotton fabrics with extracts of Xylocarpus granatum, a mangrove plant with a long history of use in leather tanning and textile dyeing. X. granatum bark was extracted and spray-dried, yielding a tannin-rich, reddish-brown powder. This powder proved a suitable colorant for the natural dyeing of cotton with promising color fastness properties to wet treatments (washing, water, sea water, and perspiration), hot pressing, crocking, and light exposure. However, the dye alone produced only weak levels of coloration and therefore metallic salt mordants were employed to improve the color strength, through the formation of insoluble tannate complexes. The resulting fabric K/S values were dependent on the mordant used and exhibited the following trend: ferric sulfate > sodium dichromate > copper sulfate > potassium aluminum sulfate > no mordant, for fabrics exposed to mordants before and after dyeing. Mordanting resulted in slight variations in shade and color fastness. In most cases, the color fastness properties were preserved, except for color fastness to light and hot pressing, for which lowered ratings were found for some mordants. Stiffness and mechanical performance were not greatly affected by dyeing or mordanting, except for sodium dichromate mordanting which significantly stiffened and weakened the fabric. The ultraviolet protection factor (UPF) of all the dyed samples achieved the maximum (50+) level, highlighting the excellent UV shielding properties of the fabric. Overall, X. granatum bark extract is a promising, effective colorant for the natural dyeing of cotton in terms of appearance, fastness, and physical characteristics.