The Extension of Unoriented Nylon 66 Filaments: Part II: Phenomenological Relationships

Abstract

Previous experimental investigations of cold drawing have employed two different techniques, (i) a study of load-elongation curves obtained on a constant-rate-of-elongation apparatus, and (ii) the operation of a two-roller drawing machine. In the first case, the length of yarn is fixed and the travel of the neck is followed along this length. In the second case, the neck is fixed in space by adjusting the speed and draw ratio applied to the traversing fiber. A third experimental method is to apply a constant load to an undrawn fiber and measure the increase in length with time (creep). In this experiment, cold drawing is observed by a marked yield region on the logarithmic time scale. Prior to the yield point, there is a region of uniform extension or pre-yield creep. Following the yield point, there is also a region of uniform extension or post-yield creep. These creep curves can be used to predict cold drawing behavior on both a two-roller drawing machine and a constant-rate-of-elongation apparatus. In particular, the location of the neck between feed and draw rolls, the drawing tension, and the speed dependence can be understood. These concepts are illustrated using results on nylon 66 monofilaments.