Dye-Fibre attachment theory

The extent of the dye fixation as well as the fastness properties of the obtained dyeing are determined by the mode of interaction between the dye molecules and the textile fibres by one or more of the following mechanisms:

1. Ionic bonding – Protein fibres with acid and basic dyes

2. Covalent bonding – Reactive dyes with cellulosic fibres

3. Hydrogen bonding – Direct dyes with cellulosic fibres

4. Insolublisation of pre-dissolved dyes following their entry into fibres – Vat and Sulphur dyes with cellulosic fibres

5. Adsorption of dye-vapour – volatile disperse dyes with polyester

Application class, textile fibres and dye-fibre attachment are summarised in Table

Application class	Textile Fibres	Mode of fixation
Reactive	Cellulosic and Wool fibres	Covalent bonds
Direct	Cellulosic fibres	Hydrogen bonds
Acid	Protein fibres, Nylon and Polyurethane	Ionic bonds
Basic	Acrylic and Basic dye able PET	Ionic bonds
Disperse	Polyester, cellulose acetates and other synthetic fibres	Hydrophobic interaction, Hydrogen bonds and van der Walls forces
Vat	Cellulosic fibres	In-situ deposition by oxidation
Sulphur	Cellulosic fibres	In-situ deposition by oxidation
Natural	Cellulosic and Protein fibres	Complexation with mordant