Study of the colouristic capacity of the natural annatto dye in dyeing polyester fabrics and recycled yarns

Abstract The textile sector has been the subject of research aimed at discovering more sustainable alternatives to harmful chemicals, and coloration technologies. In this study, the colouristic capacity of the natural annatto dye was evaluated in 100% polyester (PES) fabrics and in 100% PES fabrics with recycled thread. A comparative characterisation of a dye extracted directly from annatto seeds with a commercial natural dye was also carried out. The dyeing processes were conducted with the commercial natural dye at temperatures of 105, 110 and 115°C and pH levels of 4, 4.5 and 5, following a 2 2 full experimental design including two axial points and triplicate in the central point. The dyed fabric samples were subjected to wash fastness and dry and wet rubbing tests, to evaluate colour quality. The results were analysed using Statistica software, and the 100% PES fabric samples with the best exhaustion values (91.9%), colour intensity ( K/S ) values (1.44) and satisfactory fastness values were dyed at a temperature of 117°C and pH of 4.5. Furthermore, samples with recycled PES yarn were dyed and compared with conventional PES yarn, demonstrating similar dye and fastness characteristics, as well as intense coloration.