Concept:Disperse dyes are non-ionic, low-molecular-weight organic compounds applied as fine colloidal dispersions that dissolve into hydrophobic synthetic polymers at high temperatures.
Formula / Reaction:$$\text{Dye (Aqueous Dispersion)} \xrightarrow{130^\circ\text{C / Pressure}} \text{Dye (Solid Solution in Polyester)}$$
Solution:- Polyester (PET) lacks ionic dye sites and is highly crystalline.
- Non-ionic disperse dye molecules diffuse into the thermally swollen amorphous regions of the polyester matrix.
Why other options are incorrect:- Acid dyes: Anionic salts that cannot penetrate hydrophobic, non-polar polyester fibers.
- Basic dyes: Water-soluble cationic salts used primarily for polyacrylonitrile (acrylic) and wool.
- Azo direct dyes: Highly polar, water-soluble dyes designed for hydrophilic cellulosic fibers like cotton.
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