FLOW-DRAWING OF POLY(ETHYLENE-TEREPHTHALATE)

The drawing characteristics of poly(ethylene terephthalate) (PET) yarns spun at 1000 and 3000 m/min and film cast at 10 m/min have been studied as functions of drawing temperature up to 200°C and drawing rate up to 50 min−1. The fiber spun at 1000 m/min and the film had very low degrees of pre‐orientation and flow‐drawing occurred 20 to 30°C above their respective glass transition temperatures, for which the drawing tension dropped to almost zero and the resulting drawn samples were found to be amorphous and isotropic. In these samples, flow‐drawing could be prevented if they were drawn at relatively low temperatures or high strain rates. The partially‐oriented yarn spun at 3000 m/min, which had higher pre‐orientation, did not exhibit flow‐drawing under the conditions used. Flow‐drawing apparently occurs due to molecular relaxation processes, which predominate if the drawing temperatures are high, the strain rates are low, and the PET precursor has a low degree of orientation. Copyright © 1990 Society of Plastics Engineers