Textile Finishing Chemicals

PDMS emulsions adsorb onto fiber surfaces via weak van der Waals forces, providing temporary softness and smoothness that diminishes after washing. Amino silicone oils bond more strongly to negatively charged fibers (especially cellulosics) via electrostatic attraction of protonated amines, giving better wash durability. Epoxy-terminated silicones form covalent bonds to fiber hydroxyls for the highest wash durability.

High-amine grades (0.5–1.5 mmol/g) give maximum softness and are used for towels, knitwear, and dark-colored fabrics. Low-amine hydrophilic grades (0.05–0.2 mmol/g) are used for white and light-colored fabrics where yellowing under heat and UV must be avoided. The optimal amine value is a balance between softness, yellowing, and rewettability requirements.

The pad-dry-cure process is most common: fabric is padded through a bath containing 5–30 g/L active silicone, squeezed to 70–80% wet pickup, dried at 100–120°C, then cured at 150–170°C for 60–90 seconds. For exhaust application, cationic silicone emulsions are added to the dyebath at 1–3% owf in the final rinse cycle. Cure temperature is critical for reactive silicones (amino, epoxy) to achieve full bonding.