Colorimetric Quantification of Virgin and Recycled Cashmere Fibers: Equilibrium, Kinetic, and Thermodynamic Studies

Cashmere is byword for soft, luxury, and expensive stylish clothes. Objective and quantitative methods to identify and possibly quantify recycled cashmere are crucial to discourage adulteration of high-quality virgin cashmere with cheaper recycled fibers. Available analytical methods for the identification of recycled and virgin fibers are currently confined to subjective assays. This work investigates objective and reliable methodologies to quantify the amount of recycled cashmere in blend with virgin one, based on the different dye absorption capacity of recycled and virgin fibers. Pure virgin and recycled cashmere fibers were stained with different amounts of C.I. Direct Red 7 in different conditions, and the exhaust dyebaths were analyzed by UV-visible Spectroscopy in order to quantify the residual unabsorbed dye. Then, the method was applied to blends of different proportions of virgin and recycled cashmere with a correlation of R2 = 0.95.