Residual Torque and Yarn Spirality Testing

Residual torque testing measures the rotational energy stored in a twisted yarn that causes snarling, stitching problems, and fabric spirality in knitted structures. Zweigle G566 residual torque tester: 500 mm yarn loop hung vertically under 0.5 cN/tex tension, free end released → yarn rotates to equilibrium → angle of rotation θ° measured (0° = perfectly balanced, 45° = moderate torque, >90° = severe torque causing processing problems). Single Z-twist ring yarn residual torque 30–90° typically — torque directly related to twist factor (αe 4.5 → 80–100°, αe 3.2 → 25–45°). Fabric spirality (ASTM D3882, ISO 16322-2: measure angle between wale direction and vertical in relaxed knitted fabric — spirality <5° = acceptable, 5–8° = borderline, >8° = rejected by most brands) is caused by residual yarn torque: single Z-twist cotton jersey fabric spirality 8–15° before relaxation washing; plied 2/1 Z/S or compact ring yarn (40–60% lower torque than standard ring) reduces spirality to <5°. Torque-balanced yarn technologies: air-entangled bicomponent yarn (SDL Atlas air-jet interlacing, 6 bar pressure, 100 entanglements/m) achieves near-zero torque; dual-twist yarn (Repco friction spinning) with helical fibre disposition; core-spun elastane (3–5% elastane, 5× draft, Ze-wrapped with cotton roving) produces balanced structure. Sewing thread torque (ISO 9236-1, needle thread loop test, 100 rotations untwist test): high-torque thread >45° causes seam puckering and stitch loop distortion in high-speed industrial sewing at 5,000–8,000 spm — torque-balanced sewing thread required for flat seam quality in activewear.