Effect of zone drawing on the structure and properties of melt-spun poly(trimethylene terephthalate) fiber

Melt-spun poly(trimethylene terephthalate) (PTT) fibers were zone-drawn and the structures and properties of the fibers were investigated in consideration of the spinning and zone-drawing conditions. The draw ratio increased up to 4 with increasing drawing temperature to 180 degreesC, at a maximum drawing stress of 220 MPa. Higher take-up velocity gave lower drawability of the fiber. The PTT fiber taken up at 4000 rpm was hardly drawn, in spite of using maximum drawing stress, because a high degree of orientation had been achieved in the spinning procedure. However, an additional enhancement of birefringence was observed, indicating a further orientation of PTT molecules by zone drawing. The exotherm peak at 60 degreesC disappeared and was shifted to a lower temperature with an increase in the take-up velocity, which means that the orientation and crystallinity of the fiber increased. The d-spacing of (002) plane increased with increasing take-up velocity and draw ratio, whereas those of (010) and (001) planes decreased. In all cases, the crystal size increased with take-up velocity and draw ratio. The cold-drawn PTT fiber revealed a kink band structure, which disappeared as the drawing temperature was raised. The physical properties of zone-drawn PTT fibers were improved as the draw ratio and take-up velocity increased. (C) 2001 John Wiley & Sons, Inc.