Behavior of Nylon 6 Filaments in Cold Drawing

The necking and molecular orientation of nylon-6 filaments in an industrial cold drawing process were studied by birefringence (Δn) of drawn filaments. The relation between the properties of drawn filaments and the drawing conditions were also considered, and the following results are obtained:(1) When the filament is drawn with draw ratio of 4.0, its birefriengence (Δn) becomes the maximum immediately after the necking point.(2) Δn reaches the e4uilibrium at the point where the filament speed is equal to the drawing speed.(3) Δn becomes smaller between the drawing rolers and the winding bobbin.(4) When the drawn filament is kept wound under tension, Δn increases with the lapse of time and reaches a constant value.(5) Local Δn increases asymptotically with the distance from the feed roll when the yarn is drawn under the draw ratio 3.0, but Δn is approximately constant under the draw ratios of 3.5, 3.6 and 4.0. Δn of filaments drawn at high temperature is greater than that of yarns drawn at low temperature.(6) The effect of the draw conditions, e.g., the draw ratio, the humidity in a drawing chamber etc., on Δn is also observed.(7) Physical properties of filaments obtained under different drawing condition show that the molecular orientation is closely related to the filament properties.(8) The drawing tension, molecular orientation and crystalization with various draw ratios are observed and their effects are also analysed.(9) The winding tension on a draw-twisting bobbin was estimated from Δn of the wound filament.