Major
Chemistry
Advisor
Bide, Martin
Advisor Department
Textile, Fashion Merchandising and Design
Date
5-2019
Keywords
Cationic cotton; indigo dye; indigo; cotton; spectral analysis
Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial 4.0 License
Abstract
50 shades of blue: A study on the uptake of indigo by cationic cotton
Indigo (as a natural dye, and more recently as the synthetic version) has been used for centuries. Its application to cotton is inefficient – the dye has low substantivity for the fiber. In practice, this is overcome by applying the dye in multiple steps. Other dyes (notably the widely used class of ‘reactive dyes’) applied to cotton require the use of much salt, and large amounts of energy and water. The recent development and commercialization of cotton modified with a cationic (positive) charge has offered a means to avoid those environmental disadvantages. This project sought to examine if cationic cotton would offer similar advantages in overcoming the limited uptake of indigo.
In the study, indigo was applied to both unmodified and cationic cotton. Experimental parameters of time, temperature, pH, and amount of dye applied were varied, and the amount of dye taken up by the fibers determined both as color depth on the fabric, and spectrophotometric analysis of dye remaining in the dyebath. As well as simply providing uptake amounts, those data for long dyeing times were analyzed as dyeing isotherms, which allowed a hypothesis of the dye-fiber interactions occurring in both unmodified and cationic cotton. The penetration of color into the fabric/yarn/fiber structures was determined by microscopical cross-section. The colorfastness of the dyed fabrics (crocking) was also assessed, in order to determine how each fabric responds differently to the dye.
The shades achieved by cationic cotton were significantly darker than those achieved by untreated cotton for all depths of shade applied. A given depth of shade took less time and a lower concentration of dye on cationic cotton than on cotton. This was found to be true for tests run at 1 hour and tests run at 24 hours, showing that cationic cotton responds better than cotton over variables of both varying time and varying concentrations of dye bath. However, the cationic cotton samples had lower fastness to crocking than the regular cotton, both wet and dry. This suggests that the dye is more heavily confined to the fiber surface in the cationic cotton.
It is clear that cationic cotton takes up indigo more efficiently and effectively than untreated cotton.