In the diploma thesis, the pH responsiveness of cotton and polyamide 6 fabrics dyed with the indicator dye methyl orange (MO) was investigated. The colour response of the dyed fabrics to the change in pH was determined spectrophotometrically by immersing the dyed samples in buffer solutions with different pH values. The exhaustion of the dye, the colour depth and the dyeing levelness were also determined spectrophotometrically. The colour fastness of the dyed fabrics to dry and wet rubbing, hot pressing, domestic and commercial laundering, and artificial light was tested according to the SIST EN ISO standards.
The indicator dye MO was successfully applied to the cationised cotton fabric and the polyamide 6 fabric using the exhaust dyeing process. pH responsive fabrics were developed. Cationisation of the cotton fabric before dyeing increased the adsorption of the dye MO on the fabric. Compared to the dyed cotton fabric, the dyed polyamide 6 fabric exhibits very good colour fastness to dry and wet rubbing, hot pressing, domestic and commercial laundering and artificial light. The colour response of the dye MO bound on the cationised cotton fabric to the change in pH is better than the colour response of the dye MO bound on the polyamide 6 fabric.
The results of the study show that the protonation and deprotonation of the dye bound to the fibres and the associated colour response of the investigated fabrics to changes in pH depend on the strength of the dye-fibre interactions and the wettability of the dyed fabric with the buffer solution.
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