Fabric dyeing with colorimetric pH-responsive colours

This paper explores the possibility of dyeing textile fabrics with halochromic dyes.Five different halochromic dyes were tested: bromocresol purple, m-cresol purple,chlorophenol red, curcumin and bromothymol blue. Preliminary dyeing was carriedout on wool, polyacrylonitrile, polyester, polyamide 6.6, cotton and cellulose acetateat 100°C for 40 minutes to evaluate affinity. All the dyes showed good affinity towool and polyamide 6.6. Cotton required a mordant phase before dyeing. Washingand light fastness were evaluated for the dyed fabrics, as well as colour changesat different pH values. Some fibres displayed good dye fastness and halochromicproperties. Bromothymol blue was selected to dye polyamide 6.6 and cotton fabrics.The dyed fabrics displayed good halochromic properties across a pH range of 4 to10. Cotton fabrics exhibited an immediate colour change; polyamide 6.6 changedcolour after several minutes. An industrial dyeing process was performed on naturalcellulosic fibres. The results confirmed the possibility of scaling up the process withregard to textile applications of halochromic dyes.