Indigo dyeing of polyester (PET) - pH effects

摘要

Polyester (polyethylene terephthalate [PET]) fabric was dyed with indigo dye through an exhaust technique at different pH values. At different pH values, different forms of the indigo existed in the solution, each one having different substantivity for the fibre. The non-ionic form had the highest substantivity for polyester. The fibres could best be dyed in the acidic pH range. Chemistry of the dyebath as well as fibre was considered to explain the effect of pH on colour strength. The results suggest that hydrogen bonding is the main reason for the exhaustion of dye onto the polyester fibre. Hydrogen bonding is formed between the hydroxyl group of the leuco vat acid and the ester and aromatic ring of the PET fibre.