Polyester as-spun fihers were drawn with a draw ratio ( λ ) of 1.0-4.0 at ambient temperature. Their morphological structures have been studied by means of differential scanning calormetry (DSC) and X-ray diffraction.From DSC measurements

Tm was found to be 530.2 ± 0.4 k and there was a linear relationship between △Hm and λ:△Hm = 39.40 λ 5.05λ(J△g).There was little change of Tc with draw ratio.A broad exothermic region was observed in the zeighborhood of Tg. Its area increases with λ

and its lower temperature limit decreases with λ.The exothermic region is attributed to the crystallization of the oriented moleculat chains in the amorphous samp-les

i.e. the so-called “third phase”.