Molecular Weight Dependence of Fiber Structure Development in the Laser Drawing of Poly(ethylene terephthalate) Fibers

The effect of molecular weight on fiber structure development during the continuous neck-drawing of the amorphous poly(ethylene terephthalate) (PET) fiber was investigated by fiber temperature measurements and online WARD analysis. The fiber temperature was also simulated using the energy balance equation. The simulated temperature increased differently with molecular weight immediately after the neck point, while the measured temperature showed no difference. The difference in the simulated temperature was caused by the potential energy increase with increasing molecular weight, which would result in a retardation effect in the initial stage of fiber structure development. Online X-ray measurements were carried out with a time resolution of 0.5 +/- 0.06 ms. A two-dimensionally ordered mesophase was formed within 1 ms after the neck point and developed into a microfibrillar structure. The time required for the disappearance of the two-dimensionally ordered structure increased with increasing molecular weight, leading to a retardation effect. No molecular weight dependence was observed in the rate of transformation from the two-dimensionally ordered structure to the PET crystal. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1653-1665, 2009