Fiber Properties and Dyeing

Study Notes

Presence of acetate side chains in acetate fibers makes them softer and easier to work with than cotton, but provides fewer binding sites for dye molecules.
Nylon is a polyamide made up of hydrocarbon repeating units joined together by highly polar amide functional groups, providing sites for hydrogen bonding to dye molecules.
Polyester repeating units are joined together by ester functional groups.

Four types of forces of attraction or bond are at work in dyeing: ionic bonds, covalent bonds, hydrogen bonding, and Van Der Waals forces.
Ionic bonds: interaction between negative center of dye with positive center of fiber and vice versa.
Covalent bonds: actual chemical bond between fiber and dye through crosslinkage agents such as 2,4,6-trichloro triazine (reactive dye).
Hydrogen bonding: primarily electrostatic force of attraction between hydrogen atom covalently bound to electronegative atom or group, and another electronegative atom bearing a lone pair of electrons.
Van Der Waals forces: due to interaction between π-orbitals of dye and fiber, very weak forces.

Direct dyes: moderate washing, moderate light, good dry cleaning, good perspiration, good rubbing.
Disperse dyes: good washing, good light, good dry cleaning, good perspiration, good rubbing.
Reactive dyes: good washing, good light, excellent dry cleaning, excellent perspiration, good rubbing.
Vat (except indigo) dyes: excellent washing, excellent light, good dry cleaning, excellent perspiration, good rubbing.
Azoic dyes: good washing, good light, moderate dry cleaning, good perspiration, moderate rubbing.

Protein fibers: wool is a protein made up of amino acid repeating units with acidic or basic side chains that are ionized (charged), providing excellent binding sites for dye molecules.
Cotton is a polysaccharide composed of glucose units with three polar hydroxyl groups per glucose repeating unit, providing multiple sites for hydrogen bonding to ionic and polar groups in dye molecules.
Acetate fibers: cellulose with some –OH groups replaced by acetate groups (–OCOCH3).

Color fastness: resistance of the color of textiles to different agents during manufacture and use.
Common color fastness tests: washing, light, sublimation, perspiration, and rubbing.
Assessment of color fastness: uses Grey Scale to assess changes in color and staining, with ratings from 1 (poor) to 5 (excellent).