Quenching and Filament Solidification
topic
Extruded filaments are quenched by cross-flow (or radial-flow for POY) air at 20–25°C, 0.4–0.6 m/s velocity, over a 1–1.5 m quench zone. Solidification occurs when melt cools below Tg (67°C). Quench uniformity determines denier uniformity (CV%) and birefringence distribution across the filament bundle. Cooling rate affects crystallinity development — faster quench produces lower crystallinity.
Role
Quenching conditions are critical determinants of filament structure uniformity, birefringence, residual stress, and downstream drawability. Non-uniform quenching is a primary cause of filament breakage and dyeability variation.