EFFECT OF INITIAL TAKE-UP SPEED ON PROPERTIES AND STRUCTURE OF AS-SPUN AND DRAWN HEAT-SET POLY(ETHYLENE-TEREPHTHALATE) FILAMENTS/

The effect of initial take-up speed on the properties and structure of both as-spun and drawn/heat-set poly(ethylene terephthalate) filament s was characterized through measurements of birefringence, percent cry stallinity, tensile properties, high temperature shrinkage, loss tange nt temperature dependence, DSC melting behavior, and wide-angle (WAXS) and small-angle X-ray scattering (SAXS). While a steady trend toward improved as-spun filament orientation and tensile properties occurred with increasing initial take-up speed, the reduced drawability of thes e more structured precursor filaments resulted in corresponding drawn/ heat-set filaments that were of relatively lower overall orientation a nd tensile strength. The observed trends in tenacity, initial modulus, and high temperature shrinkage of the drawn/heat-set filaments appear ed to be well correlated with the extent and distribution of amorphous phase rigidity as perceived through inferences made from the loss tan gent temperature dependence. The WAXS patterns of the drawn/heat-set s amples indicated that these filaments all possess a well-developed and highly oriented crystalline structure. Application of a simple two ph ase model allowed the determination of an amorphous orientation factor , which for the drawn/heat-set filaments was generally found to decrea se as the draw ratio imposed in order to achieve comparable levels of elongation to break decreased. The SAXS patterns of the drawn/heat-set filaments indicated that comparable long period spacings exist in all cases and that a transition from a four-point pattern to a two-point bar-shaped pattern occurred when the precursor filament possessed some significant amount of as-spun crystallinity. (C) 1998 John Wiley & So ns, Inc.