DYEING NYLON WITH INDIGO IN VARIOUS PH REGIONS

Abstract

Nylon (6.6) fabric was dyed with Indigo dye using an exhaust technique at different pH values. At different pH values different forms of indigo existed in solution, each one having a different substantivity for the fibre. The non-ionic form had the highest, whilst the Ionic ones had relatively less substantivity. The fibres could best be dyed in the acidic to slightly alkaline pH range. The Chemistry of the dyebath and fibre were considered, in order to explain the effect of pH on colour strength. Hydrogen bonding and ionic interactions seemed to be the main reason for the exhaustion of dye onto nylon fibre. Hydrogen bonding occurred between the hydroxyl groups and amide groups, while ionic interactions worked at low pH values between the ionized and end-amino groups of the dye and fibre respectively.