How to choose the right dye according to the fabric

Textile dyeing is more than a simple coloring process; it's a highly precise art based on science. Its core lies in a deep understanding of the chemical nature of different fibers and matching them with dyes that form strong bonds. Choosing the wrong dye can lead to dull colors, rapid fading, and poor color fastness. Therefore, "fiber-specific" dye selection is paramount.

1. Cellulose Fibers (Cotton, Linen, Viscose, etc.)

These fibers (such as cotton, linen, and viscose) are primarily composed of cellulose molecular chains, which are rich in hydrophilic hydroxyl groups (-OH) on their surfaces. This chemical property makes them particularly suitable for dyes that form covalent bonds or strong intermolecular forces.

Preferred Dyes: Reactive Dyes

Matching Mechanism: Reactive dye molecules contain reactive groups that react chemically with hydroxyl groups on cellulose fibers under alkaline conditions, forming strong covalent bonds. This highly stable bond results in vibrant colors and exceptional wash fastness in dyed fabrics, making them the mainstream choice for modern cellulose fiber dyeing. Important Dyes: Vat Dyes

Matching Mechanism: Vat dyes are insoluble in water and must be reduced to a soluble leuco form under alkaline conditions to dye the fiber. They are then oxidized to become insoluble dyes that become fixed within the fiber. They offer excellent color fastness, especially to sunlight and washing, and are often used in high-end denim (indigo) and products requiring extremely high color fastness.

2. Protein Fibers (Wool, Silk)

Wool and silk are primarily composed of protein, which contains numerous amino (-NH₂) and carboxyl (-COOH) groups within its molecular chains. This allows them to bind both anions and cations under dyeing conditions, exhibiting amphoteric properties.

Preferred Dyes: Acid Dyes

Matching Mechanism: In an acidic or neutral dye bath, the amino groups on protein fibers absorb hydrogen ions, becoming positively charged (-NH₃⁺), which then bind to the negatively charged acid dye molecules through ionic bonds. Acid dyes impart vibrant colors and excellent fastness to protein fibers, making them the primary dyes used for wool and silk dyeing.

3.Synthetic Fibers (Polyester, Nylon, Acrylic)

Synthetic fibers are typically compact and highly hydrophobic, requiring specialized dyes tailored to their unique physical and chemical properties.

Polyester (Polyester Fiber) - Disperse Dyes

Matching Mechanism: Polyester has a compact molecular structure, is highly hydrophobic, and lacks reactive groups. Disperse dyes are non-ionic, small-molecule dyes with extremely low water solubility. Under high temperature and pressure (or hot melt), the dye molecules "diffuse" into the amorphous regions of polyester as single molecules, anchoring them through hydrogen bonds and van der Waals forces, resulting in dyeing. The primary mechanisms are physical dissolution and adsorption.

Nylon (Polyamide Fiber) - Acid Dyes / Disperse Dyes

Matching Mechanism: Nylon molecules contain amino groups at their ends, similar to protein fibers. Therefore, acid dyes can be used to dye through ionic bonding, producing vibrant colors. Because it is also hydrophobic, it can also be dyed with disperse dyes, resulting in better leveling.

Acrylic (polyacrylonitrile) - Cationic Dyes

Matching Mechanism: Acrylic fibers contain negatively charged groups such as sulfonic acid and carboxyl groups. Cationic dyes (formerly known as basic dyes) ionize in aqueous solution to produce positively charged pigment cations. These bind strongly to the negatively charged groups on the fiber through ionic bonds, resulting in extremely vibrant and eye-catching colors.