SYNOPSISYarns of different inherent viscosities, in the range 0.6-1.1 dL/g, spun in industrial plants, and drawn at room temperature to obtain mesomorphic samples, have been characterized. The evolution from the mesomorphic form toward the triclinic crystalline form has also been studied by combined differential scanning calorimetry ( DSC ) , dynamic mechanical analyses (DMA), and accurate wide angle X-ray diffraction experiments. The DMA analysis of the mesomorphic samples allows better resolution of the glass transition and crystallization phenomena, which are superimposed in the DSC scans. The degree of molecular orientation in the mesomorphic samples, and the temperature of crystallization from the mesomorphic form (SO-80°C) , are essentially independent of the polymer molar mass.

SYNOPSISThe dependence on the moisture content of the glass transition temperature (T,) and of the crystallization temperature from the quenched amorphous phase ( T,) for poly (ethylene terephthalate) ( P E T ) samples is studied by differential scanning calorimetry.For low moisture contents, very large and reversible decreases of T, but small decreases of T, are observed. This indicates that the strong increase of nucleation rate observed for PET in the presence of moisture is not related to the plasticizing effect that produces significant T, changes.

SYNOPSISThe nucleating activity of antimony catalyst remnants on the melt crystallization of poly (ethylene terephthalate) (PET) is proved through comparisons, for samples with Sb concentrations in the range 180-1850 ppm, of the crystallization behaviors before and after a complete extraction of the catalyst remnants. These comparisons are performed by analysis of the crystallization peaks of differential scanning calorimetry (DSC) , by the study of isothermal crystallization kinetics from X-ray diffraction experiments, and by optical microscopy observations of the size of the spherulites. The dependence of the crystallization temperature ( T,, as evaluated by the position of the DSC peak) on the Sb concentration, reported in the literature, is shown to be largely overestimated. In particular, it is found that the T, of commercial samples are essentially unaffected by the presence of the standard concentrations of Sb catalyst remnants. 0 1993 John Wiley & Sons, Inc.

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