Filament Drawing and Orientation

Drawing process for polyester/nylon: (1) heating—filaments heated to glass transition temperature (polyester 70-90°C, nylon 60-80°C) via hot godets or steam chambers enabling molecular mobility, (2) stretching—sequential godet pairs running at increasing speeds (draw ratio 3.0-5.5× for polyester, 3.5-4.5× for nylon) elongating filaments, aligning polymer chains along fiber axis, (3) heat setting—final godets at elevated temperature (180-210°C polyester, 160-190°C nylon) relaxing internal stresses, stabilizing structure, (4) winding—precision winder creating dye packages or beam packages. Drawing effects: crystallinity increases (as-spun 20-30% → drawn 40-55% polyester), orientation increases (birefringence 0.02-0.04 → 0.15-0.18), tenacity increases (1.5-2.5 g/den → 4.5-6.0 g/den), elongation decreases (80-150% → 15-30%), and diameter reduces (proportional to draw ratio).