Polyester Staple Fibre Testing

Polyester staple fibre (PSF) incoming quality testing at spinning mills verifies 12 parameters against purchase specification: linear density (dtex ±0.05, ISO 1973 gravimetric or Vibromat resonance, 50 fibre measurements), cut length (mm ±1 mm, image analysis or manual combing — 38 mm for cotton-type, 51 mm for medium staple, 64 mm for long staple blending), tenacity (cN/tex ±2, ISO 5079 Favimat+, 50 tests), elongation (% ±5, same instrument), crimp frequency (crimps/cm ±1, ISO 38), crimp modulus (% ±5), boiling water shrinkage (BWS ±0.5%, ISO 10799), moisture regain (% oven-dry, standard 0.4% for PET, elevated >0.8% indicates hydrolysis or surface finish problem), finishing oil content (%, Soxhlet extraction, optimum 0.12–0.18% for cotton-system processing), matted or fused fibre count (% by wet sieving, <0.5% for quality grade), colour (CIE L*a*b*, D65/10°, L* >90 for white fibre, b* <2.0 for no yellow cast), and electrical resistance (Ω/cm, <10⁸ for antistatic grade). Differential Scanning Calorimetry (DSC, ISO 11357-3) on PSF: melting peak Tm 254–258°C confirms PET versus recycled or co-polymer content; crystallinity by ΔHf/ΔHf°×100 (ΔHf° = 140 J/g) — drawn PET staple crystallinity 40–50%, bicomponent PE/PET shell-core crystallinity 20–30% in PE shell. Cross-sectional geometry (SEM, scanning electron microscopy, 15 kV, gold-sputter coated): circular, trilobal, hollow (hollow% = 20–30% for thermal insulation fill fibre), 4DG grooved — cross-section verification prevents substitution of lower-cost round fibre for higher-value functional profiles.