DTY Crimp Contraction and Stability Testing

Draw-textured yarn (DTY) crimp testing measures the dimensional change between extended and relaxed states quantifying the bulk, stretch, and thermal stability of false-twist textured polyester and nylon filament yarns. Crimp contraction CC% (ISO 2062 adapted, BISFA method E4.1, Lenzing method): cut 500 mm DTY sample, hang vertically under 0.001 cN/dtex pretension (low tension, 0.02 cN for 167 dtex) for 30 seconds → measure length L₁ → increase tension to 0.05 cN/dtex (extended, 8.4 cN for 167 dtex) for 30 seconds → measure L₂ → CC% = (L₂ − L₁) / L₂ × 100. Target CC%: apparel DTY for knitting 22–32%, stretch woven 15–22%, microfibre woven 12–18%; too high CC% (>35%) causes uneven fabric surface; too low (<12%) indicates under-texturing giving hard handle. Crimp stability CS% (same specimen after boiling water treatment 30 min, redry at 60°C, remeasure CC% → CS% = CC%after / CC%before × 100): CS > 80% for dyeing-stable DTY — low CS (< 65%) indicates inadequate 2nd heater temperature in texturing machine causing crimp loss during 130°C jet dyeing, producing uneven fabric shrinkage and surface variation. Textured yarn bulk (ASTM D4031, 110 m hank under 0.04 cN/dtex, hot air oven 120°C 5 minutes, measure hank length decrease — bulk% = length decrease / original length × 100): BCF carpet yarn bulk 30–45% for premium cut pile carpet; micro DTY apparel bulk 10–20%. DPF (denier per filament = total dtex / filament count, measured by cross-section counting in SEM): 0.5–1.5 DPF for microfibre, 1.5–4.0 DPF standard, >8 DPF coarse filament — DPF determines fabric softness and moisture transport by capillary action.