Synthetic Fibre Finishing and Functional Modification

Synthetic fibre finishing and functional modification encompasses the physical, chemical, and surface engineering treatments applied to synthetic fibres and fabrics to overcome inherent limitations (hydrophobicity, static, flammability, UV degradation) or add value-added functionality (moisture management, antimicrobial activity, phase-change thermal regulation, electrical conductivity) — transforming commodity synthetic fibres into specialty products commanding $0.50–5.00/m² price premiums. Key limitations of synthetic fibres requiring modification: polyester and nylon hydrophobicity (moisture regain 0.4% PET, 4% PA6 — versus 8% cotton, 15% wool) causes slow moisture transport, static build-up (surface resistivity >10¹³ Ω·cm for PET versus <10¹⁰ Ω·cm threshold for static-free performance), body odour retention (bacterial growth on moisture-trapped fibre surface); polypropylene complete hydrophobicity (0% moisture regain) prevents dyeing and limits comfort. Moisture management engineering: cross-section modification (DuPont Coolmax 4-channel PET fibre, Unifi REPREVE moisture-wicking microfibre) — capillary channels with width 8–15 µm transport sweat via capillary action to fabric outer surface; wicking finish (silicone-free hydrophilic finish, Huntsman Phobotex FTC, 5 g/L pad-dry-cure 170°C, reduces PET water contact angle from 80° to 20°, wash durable 30 wash cycles); fibre surface plasma treatment (atmospheric plasma, 100–200 W/m², creates -OH and -COOH groups on PET surface, contact angle reduction 80° → 15° — durable without chemistry addition). Antimicrobial finishing: silver ion (AgNO₃ exhaustion or nanosilver coating), zinc oxide nanoparticle (ZnO, photocatalytic antimicrobial), PHMB (polyhexamethylene biguanide, 0.5–1.0% owf, 99.9% Staphylococcus aureus kill rate ISO 20743). Phase-change thermal regulation (Outlast, Microtek): microencapsulated paraffin wax PCM (octadecane, Tm 28°C, heat of fusion 230 J/g) padded or incorporated into acrylic or polyester fibre matrix — absorbs 230 J/g body heat on warming, releases same on cooling → ±3°C temperature buffering effect (NASA-derived technology, ASTM D7024 thermal regulation measurement).