Effect of Crystallinity and Orientation on Oscillation During Drawing of Polyethylene Terephthalate

Abstract

Stress oscillations have been observed in cold-drawn synthetic monofilaments and films. The effects of these oscillations on cross-section and lengthwise filament properties have been under investigation. Mathematical models based on heat transfer and theory of elasticity have been proposed by some investigators. But, quantification of these micro-stress-oscillations has not been completed. Alteration of filament structure by drawn oscillations may change optical, thermodynamic, chemical, and tensile properties. Micro-stress-oscillations during cold-drawing were investigated in polyethylene terephthalate monofilaments with various crystallinities and orientations. Micro-stress-oscillations observed were quantified on the basis of average oscillation period, and maximum, minimum, and average oscillation amplitude. Results showed that drawing rate and orientation had the greatest effect on the occurrence of micro-stress oscillation. The frequency of the oscillations increased as the drawing rate decreased and also with the decrease of filament orientation. Crystallinity and yield load did not show any appreciable effect on the occurrence of micro-stress-oscillation. Oscillations altered the filament optical properties, light transmission, and reflection.